To make any engineered device, structure or product, you need the right materials. Materials science teaches us what things are made of and why they behave as they do. Materials engineering shows us how to apply knowledge to make better things and to make things better.

The discipline of investigating the relationships that exist between the structures and properties of materials. Thus, Material Science is the branch of applied science dealing aforesaid properties of solid engineering materials. Whereas material engineering is the discipline of designing or engineering the structure of a material to produce a predetermined set of properties based on established structure-property correlation.

Four Major Components of Material Science and Engineering:

Ø Structure of Materials

Ø Properties of Materials

Ø Processing of Materials

Ø Performance of Materials

1.1 Introduction and Scope of Civil Engineering Material

Civil Engineering material is primarily concerned with the development of new or improved Civil Engineering structures such as buildings, bridges, roads, sewers, dams, airports. It can be used to repair existing structures that may be damaged due to, for example, attack by our aggressive environment, structural overload, earthquakes, storms, etc. The scope of civil engineering material is based on the field of civil engineering.

1.2 Types of Civil Engineering Materials (metals, timber, ceramics, polymers, composites)

Engineering Materials can be classified as following:

A. Civil Engineering Materials

Examples: Building Stones, Bricks and clay product, cementing materials: Lime and Cement Concrete, Mortar, Timber

B. Electrical Engineering Materials:

Examples: Copper, aluminum, iron and steel etc.------- Conductors:

Asbestos (A fibrous amphibole; used for making fireproof articles), Bakelite (type of plastic), mica, varnishes, and air etc. Insulator:

Iron, Nickel, cobalt, etc------ Magnetic materials.

C. Mechanical Engineering Materials:

Examples: Cast iron, steel, lubricating materials etc.

Other types of Construction Materials are:

1. Metals: It may be further divided as:

Ø Ferrous Metals: Metals containing iron are called Ferrous Metals. Examples: cast iron, wrought iron and steel.

Ø Non-ferrous Metals: Metals not containing iron are called as Non-ferrous metals, Examples: Copper, aluminium, zinc etc.

2. Non-metals: Building stones, cement, concrete, rubber, plastic, Asbestos etc.

3. Alloys: Product of more than one element is known as Alloys. Steel is an alloy of iron and carbon.

Ferrous Alloys: Product of ferrous metal and any other element is called ferrous alloy, Examples: silicon steel, high speed steel, spring steel etc.

Non-ferrous Alloy: Product of non-ferrous metal and other element is called non-ferrous alloy. Examples: brass, bronze, duralumin etc.

4. Timber: Timber is another name for wood, whether still standing in the form of trees or felled and turned into boards for construction. Some people may also refer to timber as lumber, or differentiate between timber as unprocessed wood and lumber as cut wood packaged for commercial sale. The timber industry around the world is huge, providing wood for a variety of products from paper to particleboard.

Uses: Cladding, Boards, Column, Beams

5. Ceramics Materials: Ceramics Materials: A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). The essential engineering properties of ceramics are that they have an ability to withstand high temperatures and retain their high strength and rigidity. Ceramics also offer electrical and insulating properties. Ceramics are phases, inorganic nonmetallic materials fabricated by shaping the powder with or without pressure into a compact, subjected to temperature treatment (sintering). Example: silica, soda lime glass, concrete cement, ferrites (i.e. solid solution), garnets (i.e. mineral), MgO, CdS, ZnO, SiC, etc.

6. Polymers: A polymer is a chemical compound or mixture of compounds consisting of repeating structural units created through a process of polymerization. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper. The list of synthetic polymers includes synthetic rubber, PVC.

7. Composite materials: Composite materials (also called composition materials or shortened to composites) are materials made from two or more constituent materials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure. Composite materials are generally used for buildings, bridges, bathtubs, and storage tanks, cultured marble sinks and countertops.

8. Organic Materials: These materials are derived directly from carbon. They usually consist of carbon chemically combined with hydrogen, oxygen or other non-metallic substances. Example: Plastics, PVC, polythene, fibre: terylene, nylon, cotton, natural and synthetic rubbers, leather etc.

1.3 Properties of Civil Engineering Materials

Following properties of material will be discussed here:

1. Physical Properties

2. Mechnical Properties

3. Thermal Properties

4. Electrical Properties and

5. Magnetic Properties

1. Physical Properties: It consist followings:

(a) The melting and freezing point: The melting or freezing point of a pure metal is defined as temperature at which the solid and liquid phases can exist in stable equilibrium. When a metal is heated to melting point, the liquid phase appears, and if more heat is supplied, the solid melts completely at constant temperature. The freezing of a pure liquid exhibit the phenomenon of super-cooling. Use of mercury in thermometer, manometers arises from it’s low melting point, while use of tungsten filaments in incandescent light bulbs in possible because of it’s extremely high melting point.

(b) Boiling Point: The boiling point of a liquid is the temperature at which it’s vapour pressure equals to one atmosphere. The boiling points of the metals except mercury are high. The boiling point of zinc is 907^oC & cadmium is 865^oC .

(c) Density: Mass per unit volume is termed as the density. In MKS, it’s unit is kg/m³

Mass per unit volume of a material in it’s natural state is called Bulk Density. Some building materials are having following values of bulk densities:

Material	Bulk Density (KN/m³)
Granite	25 to 27
Clay Brick	16 to 18
Sand	14.5 to 16.5
Gravel	14 to 17
Limestone(dense)	18 to 24
Concrete (light)	5 to 18
Concrete (heavy)	18 to 25
Steel	78.5
Plastic material(porous)	0.2 to 1.0
Pinewood (conifer tree)	5 to 6

Note: The ratio of bulk density of a material to it’s density is called density Index. The density index of most of building material is less than unity.

(d) Specific gravity: Specific gravity is the ratio of the density of a substance to the density (mass of the same unit volume) of a reference substance.

(e) Opacity: Opacity is the degree to which light is not allowed to travel through.

(f) Porosity: The degree by which the volume of material is occupied by pores is indicated by the term porosity. The strength, bulk density, durability, thermal con-ductility etc. of a material depends on it’s porosity.

(g) Water absorption: It is the ability of material to absorb and retain the water. It mainly depends on the volume, size and shape of pores present in the material.

(h) Water Permeability: It is the capacity of material to permit water to pass through it under pressure.

(i) Fire resistance: It is the ability to resist the action of high temperature without losing it’s load bearing

capacity.

(j) Durability: It is the property of material to resist the combined action of atmospheric and other factors.

(k) Refractoriness: It is the ability of a material to withstand prolonged action of high temperature without melting or loosing shape.

2. Mechanical Properties: Mechanical properties of engineering materials are such properties, which defines the behavior of materials under the action of load or force. The study of mechanical properties is very important in order to select the material for various engineering requirements. It consist followings:

(a) Strength: If a metal can withstand higher stresses before it’s fracture under the action of loading, it gives

it’s strength.

i.
Compressive Strength: Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. It provides data (or a plot) of force vs deformation for the conditions of the test method. When the limit of compressive strength is reached, brittle materials are crushed. Concrete can be made to have high compressive strength, e.g. many concrete structures have compressive strengths in excess of 50 MPa, whereas a material such as soft sandstone may have a compressive strength as low as 5 or 10 MPa. By contrast, a small plastic container might have a compressive strength of less than 250 N.

ii. Tensile Strength: Tensile strength is the capacity of a material or structure to withstand axially directed pulling forces. It provides data (or a plot) of force vs deformation for the conditions of the test method. When the limit of tensile strength is reached, ductile materials are fractured.

Material	*Comppressive Strength (kPa)*	*Tensile Strength (kPa)*
Bricks, hard	80000	2800
Bricks, light	7000	280
Brickwork, common quality	7000	350
Brickwork, best quality	14000	2100
Limestone	60000	2100
Portland Cement, less than one month old	14000	2800
Portland Cement, more than one year old	21000	3500
Portland Concrete	7000	1400
Portland Concrete, more than one year old	14000	2800
Sandstone	60000	2100

iii. Shear Strength: The stress component tangential to the plane on which the forces act. Shear strength is expressed in shear force per unit of area.

iv. Flexure Strength: Flexural strength, also known as modulus of rupture, bend strength, or fracture strength, a mechanical parameter for brittle material, is defined as a material's ability to resist deformation under load. The transverse bending test is most frequently employed, in which a rod specimen having either a circular or rectangular cross-section is bent until fracture using a three point flexural test technique. The flexural strength represents the highest stress experienced within the material at its moment of rupture.

v. Impact Strength: This strength is categorized to

i. The ability of a material to withstand shock loading.

ii. The work done in fracturing under shock loading: a specific test specimen in a specified manner.

A measure of the resiliency or toughness of a solid is indicated by impact strength. The maximum force or energy of a blow (given by a fixed procedure) which can be withstood without fracture, as opposed to fracture strength under a steady applied force is referred as the impact strength.

(b) Elasticity: It is the temporary deformation of materials under the action of load. This phenomenon takes places within elastic limit of materials. Steel is said to be more elastic than Rubber, because elastic limit of steel is higher than rubber. Elasticity is always desirable in metals used in machine tools and other structural members.

(c) Plasticity: It is permanent deformation of a material under the action of load. The Plasticity of a metal depends up on its nature and environmental condition. Lead (Pb) has good plasticity even at room temperature.

(d) Malleability: It is defined as the property of the metal by which if we can able to get a thin sheet without fracture that property of metal is called it’s malleability. “Gold” has good property of malleability. The following metals have malleability in decreasing order-- Gold, Silver, Aluminum, copper, tin, platinum, lead, zinc, iron, nickel.

(e) Ductility: It is defined as an ability of metal to draw into a thin wire without fracture. Under the application of load, before fracture, ductile material gives sufficient warning. Materials whose % of elongation is more than 15 are always referred as ductile material. During machining (cutting), formation of continuous chips indicates that the material is ductile. Materials which withstand high tensile stress are called ductile materials. Silver (Ag), copper (Cu), Aluminum (Al), Mild steel etc. are the example of ductile materials.

(f) Brittleness: Under the action of load, if all metal undergoes for instant fracture without giving any information to the operator then that property of metal is called as brittleness. Materials whose % of elongation is less than 5 are always referred as brittle materials. During machining, formation of discontinuous chips indicates that metal is brittle. Materials which withstand high compressive strength are called brittle. Concrete, Asbestos, glass, cast iron are the example of brittle materials.

(g) Hardness: It is defined as an ability of metal by virtue of which the metal gives resistance to cutting, bending, drilling, abrasion etc. by harder bodies then this ability is known as it’s hardness. If the metal is very hard it’s corresponding melting point and bond strength is also higher.

(h) Stiffness: It is defined as the property of metal by virtue of which a metal gives resistance to deformation (deflection) then we can say the metal is stiff. Under the application of load, if a metal deflects with a low angle of deflection, then it’s corresponding stiffness is higher and vice versa.

(i) Creep: Creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and near melting point. Creep always increases with temperature. The rate of this deformation is a function of the material properties, exposure time, exposure temperature and the applied structural load.

For example creep of a turbine blade will cause the blade to contact the casing, resulting in the failure of the blade.

Above 0.4 Tm (melting temperature) plastic deformation in metal takes place. This deformation is a function of time with the application of steady load. This Phenomenon is called creep. In short, it can be remembered as LTTE. Where, L = Load, T = temperature (constant parameters), T = Time, E = Elongation (variables).

(j) Fatigue (Endurance): Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. Fatigue occurs when a material is subjected to repeat loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators. Eventually a crack will reach a critical size, and the structure will suddenly fracture. Toughness: It is defined as an ability of metal by virtue of which how much energy it can sustain (observe) before its fracture under the action of loading. If a metal has high toughness then its corresponding impact strength is also higher, vice versa. It has already been understood that steel is tougher than cast iron. In Other word, ductile metals are having more toughness as compare with brittle materials.

(k) Abrasion Resistance: Abrasion resistance is a property which allows a material to resist wear and tear. Numerous companies manufacture abrasion resistant products for a variety of applications, including products which can be custom fabricated to meet the needs of specific users. When a product has abrasion resistance, it will resist erosion caused by scraping, rubbing, and other types of mechanical wear. This allows the material to retain its integrity and hold its form.

(l) Resilience: Resilience is the ability of a material to absorb energy when it is deformed elastically, and release that energy upon unloading. The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion.

Proof Resilience:

The maximum amount of energy that can be stored within elastic limit of the metal is called it’s proof

resilience.

Modulus of resilience.

Proof resilience per unit volume of material defines modulus of resilience.

3. Thermal Properties: It consist followings:

(a) Specific heat: The specific heat of the substance is defined as the amount of heat required to raise the temperature of unit mass of substance through 1^oC.

Q= m×s× (θ2-θ1) where “Q” is amount of heat, “m” is mass of substance and “s” is specific heat.

Substance	Specific Heat *(J/kg^oC)*
Sandy clay	1381
Quartz sand	830
Water, pure	4186
Wet mud	2512
Wood	1700

(b) Thermal conductivity: Thermal conductivity is the property of a material to conduct heat. The thermal conductivity of a metal is defined as the number of kilojoules of heat that would flow per second through a specimen 1sq. in cross-section and 1m in length when the temperature gradient is 1^oC. Silver & copper show the highest thermal conductivities among all metals. But some metals like German silver exhibit very low conductivities and hence find the applicable where heat losses by metallic conduction should be kept to a minimum. Silver is the best conductor and copper is next.

Material	Thermal Conductivity (W/m K)
Diamond	1000
Aluminum	205.0
Iron	79.5
Steel	50.2
Concrete	0.8
Wood	0.12-0.04

(c) Thermal Expansion in solids: -The thermal expansion takes place in all bodies and in all three states in matter i.e. solid, liquid and gas.

Linear coefficient of expansion: The linear coefficient of expansion of a solid is defined as the increase in length per unit length, for each degree rise in temperature.

Superficial coefficient of expansion: The Superficial coefficient of expansion of a solid is defined as the increase in are per unit area, for each degree rise in temperature.

Cubical coefficient of expansion: The Cubical coefficient of expansion of a solid is defined as the increase in volume per unit volume, for each degree rise in temperature.

(d) Thermal resistivity: It is defined as the property of material in which the resistance to flow the heat. It is the reciprocal of thermal conductivity.

4. Electrical Properties:

It comprises:

a. Conductivity: Electrical conductivity is a measure of how well a material accommodates the movement of an electric charge. It is the ratio of the current density and the electric field strength. Electrical conductivity or specific conductance is the reciprocal quantity, and measures a material's ability to conduct an electric current.

s = l / r = L/ R*A, r = R*A / L

s = J /E

b. Electrical Permittivity: A measure of the ability of a material to resist the formation of an electric field within it. When the charges are located in some other medium rather than vaccum then the force between the charges will be

Where ɛ is the absolute electric permittivity of the medium.

The force between the charges held at same distance from each other in vaccum is

Where ɛr is the relative electrical permittivity.

c. Dielectric strength: Dielectric strength is an engineering term that refers to the maximum voltage an insulating material can withstand before breaking down. It is the insulating capacity of a material against high voltage. A material having high dielectric strength can withstand sufficiently high voltage before its break.

5. Magnetic Properties:

a. Magnetic Permeability: Some materials become magnetized when placed in a magnetic field; the ability of a material to become magnetized is called magnetic permeability. An example of this is rubbing a piece of iron with a magnet: the iron will become magnetized and have its own magnetic field, meaning it has some degree of magnetic permeability.

b. Magnetic Retentivity: The property by virtue of which the magnetism (I) remains in a material even on the removal of magnetizing field is called retentivity or residual magnetism.

For ferromagnetic materials, by removing external magnetic field i.e. H = 0. The magnetic moment of some domains remain aligned in the applied direction of previous magnetizing field which results into a residual magnetism.

1.4 Material-Environment (Temperature, humidity, rain and fire) Interaction

Expansion:

Increases in temperature cause increases in volume of substance. As the average energy of particles increases, the spaces between the particles increases. They expand (increase their volume) as the temperature increases.

Contraction:

Decreases in the temperature cause decreases in the volume of substance too. As the average energy of particles decreases, the spaces between the particles decreases. They contract (decrease their volume) as the

temperature decreases. Fine Ceramics have low coefficients of thermal expansion — less than half those of stainless steels.

Warping:

Bending up and down due to different agents like deformity due to heat and moisture.

Weathering:

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity.

Crack Formation:

Crack may cause by dynamic and static stress on structure material is due to working loads, permanent load, temperature change. Permanent weathering, horizontal surfaces, dark surfaces and sharp edges increase the risk of cracking. Avoiding cracks greater than 0.1 mm is often planned in the design phase for technical reasons (e.g. waterproof concrete). This may also be necessary on aesthetic causes.

Soaking (filling the cracks without applying pressure) or injection (filling the cracks under pressure). Epoxy resins, cement paste or cement grouts are usually used for this purpose.

Corrosion:

Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. Corrosion is a gradual chemical and electro-chemical attack on a metal by its surroundings (air, industrial atmospheres, soils, acids, bases and salt solutions) and the metal is converted into an oxide, salt and some other compound.

Fe⁺²(Aq.)+ O2(g)+ 4×2H2O (l) > 2Fe2O3.XH2O(S) + 8H⁺ (Aq.)

Effect on of Strength due to fire:

Exposure to fire has significant effects on all construction materials. Wood is consumed as fuel during a fire and steel yields as it is heated to high temperatures. Concrete temperatures up to 95°C (200°F) have little effect on the strength and other properties of concrete. Above this threshold cement paste shrinks due to dehydration and aggregates expand due to temperature rise which results reduction on strength.

Effect of Strength due to combined effect of temperature and humidity:

The concrete specimens subjected to different humidity conditions at 35°C have shown some deviations in compressive strength results, however a trend of reduction of compressive strength has been observed.

Relative humidity is the ratio of the partial pressure of water vapor in an air-water mixture to the saturated vapor pressure of water at a given temperature.

2 Clay Products

CLAY: Clay is a naturally occurring aluminum silicate composed primarily of fine-grained minerals. Clay deposits are mostly composed of clay minerals, a subtype of phyllosilicate minerals, which impart plasticity and harden when fired or dried; they also may contain variable amounts of water trapped in the mineral structure by polar attraction. Organic materials which do not impart plasticity may also be a part of clay deposits. Clay minerals are typically formed over long periods of time by the gradual chemical weathering of rocks, usually silicate-bearing, by low concentrations of carbonic acid and other diluted solvents. These solvents, usually acidic, migrate through the weathering rock after leaching through upper weathered layers. In addition to the weathering process, some clay minerals are formed by hydrothermal activity. Clay deposits may be formed in place as residual deposits in soil, but thick deposits usually are formed as the result of a secondary sedimentary deposition process after they have been eroded and transported from their original location of formation. Clay deposits are typically associated with very low energy depositional environments such as large lakes and marine deposits.

Clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays, but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include both silts and clays. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4-5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg Limits. ISO 14688 grades clay particles as being smaller than 2 μm and silts larger.

Kaolinite is the most important mineral component of common clays. It is formed from all rocks containing felspar mineral ass per following reaction:

2KAlSi3O8 + 2H2O + CO2 = Al2SiO5(OH)4 + K2CO3 + 4SiO2

(Felspar Orthoclase + Carbonic acid = Kaolinite + Pot. Carbonate + Silica colloids)

Clay possesses following properties:

Ø Clay possesses plasticity when moist.

Ø Clay possesses rigidity when dried.

Ø Clay possesses strength and hardness when fired.

Classification of Clay:

1. Residual Clay: - Formed directly from rock by direct process and pure in chemical composition that is related to the parent rock.

2. Transported clay: - Formed by disintegration and decomposition of the pre-existing rocks by natural agencies followed by removal and transport of broken pieces.

Clays sintered in fire were the first form of ceramic. Bricks, cooking pots, art objects, dishware, and even musical instruments such as the ocarina can all be shaped from clay before being fired. Clay is also used in many industrial processes, such as paper making, cement production, and chemical filtering. Clay is also often used in the manufacture of pipes for smoking tobacco. Until the late 20th century bentonite clay was widely used as a mold binder in the manufacture of sand castings. Clay, being relatively impermeable to water, is also used where natural seals are needed, such as in the cores of dams, or as a barrier in landfills against toxic seepage (lining the landfill, preferably in combination with geo-textiles).

2.1 Constituents of Good Brick Earth

1. Alumina: It is the chief constituent of every kind of clay. A good brick earth should contain about 20% to 30% of alumina. This constituent imparts plasticity to the earth so that it can be molded. If alumina is present in excess, with inadequate quantity of sand, the raw bricks shrink and warp during drying and burning and become too hard when burnt.

2. Silica or Sand: It exists in clay either as free or combined. As free sand, it is mechanically mixed with clay and in combined form; it exists in chemical composition with alumina. A good brick earth should contain about 50% to 60% of silica. The presence of this constituent prevents cracking, shrinking and warping of raw bricks. It imparts uniform shape to the bricks. The durability of bricks depends on the proper proportion of silica in brick earth. The excess of silica destroys the cohesion between particles and the bricks become brittle.

3. Lime: A small quantity of lime not exceeding 5 % is desirable in good brick earth. It should be present in a very finely powered state because even small particles of the size of a pin head cause flaking (cracking) on the bricks. The lime prevents shrinkage of raw bricks. The sand alone is infusible. But it slightly fuses at kiln temperature in presence if lime. Such fused sand works as a hard-cementing material for brick particles. The excess of lime causes the brick to melt and hence it shape is lost. The lumps of lime are converted into quick lime after burning and this quick lime slakes and expands in presence of moisture. Such an action results in splitting of bricks into pieces. It acts as a flux.

4. Oxide of iron: A small quantity of oxide of iron to the extent of about 5 to 6 percent is desirable in good brick earth. It helps as lime to defuse sand. It also imparts red color to the bricks. The excess of oxide of iron makes the bricks dark blue or blackish. If, on the other hand, the quantity of iron oxide is comparatively less, the bricks will be yellowish in color.

5. Magnesia: A small quantity of magnesia in brick earth imparts yellow tint to the bricks and decreases shrinkage. But excess of magnesia leads to the decay of bricks.

Bricks:

Building bricks may be defined as structural units of rectangular shape and convenient size that are made from suitable types of clays by different processes s involving moulding, drying, burning. A good brick earth should have following compositions:

Ø Alumina or clay: 20 to 30% by weight

Ø Silica or Sand : 35 to 50% by weight

Ø Silt : 20 to 25% by weight

Remaining Ingredients which includes:

Ø Iron oxide (Fe2O3)-flux to bind particles-(4-6%)

Ø Magnesia (MgO)- Less -Yellowish color-High-decay

Ø Lime (CaO +Mg) = (4-6%)

Ø Sodium potash

Ø Manganese

Harmful Ingredients in Brick Earth:

1. Limestone and Kankar nodules: On heating, limestone is converted into lime which on contact with water swells and causes the brick to split and crumble into pieces. But a certain quantity of limestone is desirable as it binds the particle of brick together & reduces shrinkage on drying.

2. Alkalies: Alkali present in the brick earth, they lower the fusion point of clay and cause the brick to fuse, twist and warp during burning.

3. Pebbles of stone and gravel: They do not permit the clay to be thoroughly mixed and thus impair the uniformity of a brick.

4. Iron pyrites: If it present in earth decompose and oxidize in the brick and cause the brick to split.

5. Kallar or reh: It consists of sulphate of soda, mixed with common salt and carbonate of soda. It prevents the bricks from being properly baked (Dried out by heat or excessive exposure to sunlight)

6. Vegetation and organic matter: The presence of vegetation and organic matter in brick assist in burning. But if such matter is not completely burnt, the bricks become porous.

2.2 Manufacturing of Bricks:

1. Selection of suitable type of clay: Good type of bricks cannot be made from every type of clay. A suitable brick earth should have the following compositions. Aluminum (20-30%), Silica (50-60%), Iron Oxide (4- 6%), lime (4-6%) and other ingredients.

2. Preparation of Brick Earth and clay:

i. Digging: Top 20cm layer is removed due to presence of impurities. Manually or using power excavator. The excavated lumps is broken and leveled in the ground of heap of 60-120cm height.

ii. Weathering: Water is mixed in excavated soil and leave to few weeks. This improves the plasticity and strength.

iii. Blending: The clay is chemically analyzed and mixed with water if required.

iv. Tempering of Clay: Breaking of prepared clay, watering, kneading by feet of men and cattle or pugmill till making homogeneous mass.

v. Moulding of bricks: It can be done through hand moulding, ground moulding, Frog moulding, table moulding and machine moulding.

vi. Drying of bricks: It is done to make brick strong, to allow loss of moisture and to save fuel during burning stage.

Ø Air Dry: 4-10 days, 2-4% moisture remained.

Ø Sun Dried: Dried directly from sunlight. Takes 25 days to dry.

Ø
Artificial drying: Chamber drying and Tunnel Drying-2-4 Days.

vii. Burning of bricks: Dehydration-425-765°C, Oxidation-900°C and vitrification-900-1100°C- softening of Alumina and silica by fluxing agents. ( Clamps and Brick Kiln are used)-Loading, Preheating, Burning, Cooling, Unloading are the process of burning bricks. After 8 weeks ready for use.

2.3 Qualities of good bricks

Ø Well burnt bricks are copper colored and are free from cracks.

Ø They possess sharp and square edges.

Ø They are of uniform color, shape and size as per standard.

Ø When struck with each other, they produce clear metallic ringing sound.

Ø Fracture of good bricks show uniform and bright compact structure without any voids.

Ø They absorb minimum water when immersed in water. The absorption should not be more than 20 %

when immersed in water for 24 hours.

Ø Good bricks are hard on their surface and leave no impression when scratched with nails.

Ø Good bricks do not break when dropped from 1 m height.

Ø Good bricks when soaked in water and dried, do not show white patches or white deposits on their surface.

Ø The good quality bricks could be gauged easily by the percentage of bricks that get broken in transit and stacking in the course of ordinary handling (2 to 3%).

2.4 Classification of Brick:

1. First Class Brick: This type of brick has well burnt having even surface and perfectly rectangular shape. When two bricks are struck against each other a ringing sound is produced. The compressive strength shall not be less than 140 kg/cm² and its absorption after 24 hrs shall not exceed 20 %. It should show a uniform appearance. Texture and structure when seen on fracturing. It can be used for all types of construction in the exteriors walls when plastering is not required and suitable for flooring.

2. Second Class Brick: This type of brick has well burnt, even slight burning is accepted. It gives metallic- ringing sound with rectangular shape with some irregularity with uneven surface. . The compressive strength shall not be less than 70 kg/cm² and its absorption after 24 hrs shall not exceed 20-22 %. It should show slight difference in structure on fractured surface. It can be used for all types of construction in the exteriors walls when plastering is required and also suitable for interior walls and not used for flooring.

3. Third Class Brick: The third class bricks are poorly and unevenly burnt, that is, may be over burnt or under burnt. It gives dull thud (rather than metallic sound) and non –uniform shapes. It has a compressive strength of 35-70 kg/cm²and absorption between 22-25 %. It is used in ordinary type of construction and in dry situations.

4. Jhama or Fourth Class Bricks: This type or brick represents irregular shape and dark in colour due to over burning. It is strong having compressive strength of 150 kg/cm² with low absorption and porosity. These types of bricks are used in road construction (broken types), foundations and floor as a coarse aggregate material. It is not used in building construction due to distorted and irregular shapes.

5. ISI Classification: HI:

Compressive Strength: 440 Kg/cm2 Water Absorption: 5% Efflorescence: No

Tolerance in Dimension: ± 3%

Shape and Other Properties: Metallic Sound, Smooth and rectangular

HII:

Compressive Strength: 440 Kg/cm2 Water Absorption: 5% Efflorescence: No

Tolerance in Dimension: ± 8%

Shape and Other Properties: Slight deformation in shape

FI:

Compressive Strength: 175 Kg/cm2 Water Absorption: 12% Efflorescence: Very Little Tolerance in Dimension: ± 3%

Shape and Other Properties: Metallic sound, smooth, rectangular

FII:

Compressive Strength: 175 Kg/cm2 Water Absorption: 12% Efflorescence: Very Little Tolerance in Dimension: ± 8%

Shape and Other Properties: Slight deformation in shape

Compressive Strength: 70 Kg/cm2 Water Absorption: 20% Efflorescence: Very Little Tolerance in Dimension: ± 3%

Shape and Other Properties: Metallic sound, smooth, rectangular

II:

Compressive Strength: 70 Kg/cm2 Water Absorption: 20% Efflorescence: Very Little Tolerance in Dimension: ± 8%

Shape and Other Properties: Slight deformation in shape

LI:

Compressive Strength: 35 Kg/cm2 Water Absorption: 25% Efflorescence: Very Little Tolerance in Dimension: ± 3%

Shape and Other Properties: No metallic sound, smooth, rectangular, sharp edge

LII:

Compressive Strength: 35 Kg/cm2 Water Absorption: 25% Efflorescence: Very Little Tolerance in Dimension: ± 8%

Shape and Other Properties: Slight deformation in shape

Properties of Bricks:

1. Physical Properties:

a. Shape: The standard shape of an ideal brick is truly rectangular. It has well defined and sharp edges and corners. The surface of the bricks is regular and even. Special purpose bricks may, however, be either cut or manufactured in various other shapes.

b. Size: The size of the brick used in construction varies from country to country and from place to place in the same country. The basic standard size used in Nepal is 23× 13× 5.5 cm but in India the ideal size of brick 19× 9× 9 cm with which mortar joint gives net dimension of 20× 10× 10 cm.

c. Colour: The most common colour of building bricks fall under the class RED. It may vary from deep red to light red to buff and purple. A very dark shade of red indicates over burning whereas yellow colour indicates under burning.

d. Density: The density of bricks or weight per unit volume depends mostly on the type of clay used and method of brick moulding. In the case of standard bricks, density varies from 1600 kg/cubic meter to 1900 kg/cubic meter. A single brick (19× 9× 9 cm) will weigh between 3.2 to 3.5 kg.

2. Mechanical Properties:

a. Compressive Strength: It is the most important property of bricks especially because they are to be used in load bearing walls. The compressive strength of a brick depends on the composition of clay and degree of burning. It may vary from 35 kg/cm² to 200 kg/cm².

b. Flexure Strength: Bricks are often used in situations where bending loads are likely to develop in building. As such, bricks used in such places should possess sufficient strength against transverse loads. Flexure strength of bricks shall not be less that 10 kg/cm2. The best graded brick should have the flexure strength of 20 kg/cm².

3. Thermal Characteristics: Besides being hard and strong, an ideal brick should also provide adequate insulation against heat, cold and noise. The heat and sound conductivity of bricks varies greatly with their density and porosity. Very dense and heavy bricks conduct heat and sound at greater rate. They have poor thermal and acoustic insulation qualities.

4. Durability: By durability of bricks it is understood the length of time for which they remain unaltered and strong when used in construction. Experience has shown that properly manufactured bricks are among the

most durable of man-made materials of construction. The durability of bricks depends upon absorption value, frost resistance and efflorescence.

2.5 Different test for brick

1. Shape and Size Test: (I) Uniformity in Size: A good brick should have rectangular plane surface and uniform in size. This check is made in the field by observation.

(II) Uniformity in shape: A good brick will be having uniform shape throughout. This observation may be made before purchasing the brick.

To check it, 20 bricks are selected at random and they are stacked along the length, along the width and then along the height. For the standard bricks of size 190 mm × 90 mm × 90 mm. IS code permits the following limits: Lengthwise: 3680 to 3920 mm Widthwise: 1740 to 1860 mm Height wise: 1740 to 1860 mm.

2. Water Absorption Test:

a. 24 hrs. immersion cold water test: Brick specimens are weighed dry. Then they are immersed in water for a period of 24 hours. The specimen are taken out and wiped with cloth. The weight of each specimen in wet condition is determined. The differences in weight indicate the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by 100. The average of five specimens is taken.

b. 5 hrs. Boiling water test: Brick specimens are oven dried at 105°C- 115°C till it attains at constant mass. Cool the specimen at room temperature and record its weight. The specimen is immersed in boiling water for 5 hrs. and water is allowed to cool at 27±2°c with brick immersed. The specimen are taken out and wiped with cloth. The weight of specimen is determined within three minutes. The difference in weight indicates the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by 100.

3. Efflorescence Test: The presence of alkalis in brick is not desirable because they form patches of gray powder by absorbing moisture. Hence to determine the presence of alkalis this test is performed as explained below: Place the brick specimen in a glass dish containing water to a depth of 25 mm in a well-ventilated room. After all the water is absorbed or evaporated again add water for a depth of 25 mm. After second evaporation observe the bricks for white/grey patches. The observation is reported as ‘nil’, ‘slight’, ‘moderate’, and ‘heavy’ and serious.

Results:

(a) Nil: No patches

(b) Slight: 10% of area covered with deposits

(d) Heavy: More than 50 per cent area covered with deposits but unaccompanied by flaking of the surface.

(e) Serious: Heavy deposits of salt accompanied by flaking of the surface.

4. COMPRESSIVE STRENGTH TEST ON BRICK Aim: To determine the compressive strength of bricks

Apparatus: Compression testing machine, the compression plate of which shall have ball seating in the form of portion of a sphere center of which coincides with the center of the plate.

Specimens: Three numbers of whole bricks from sample collected should be taken. The dimensions should be measured to the nearest 1mm.

Sampling: Remove unevenness observed the bed faces to provide two smooth parallel faces by

grinding. Immerse in water at room temperature for 24 hours .Remove the specimen and drain out any surplus moisture at room temperature. Fill the frog and all voids in the bed faces flush with cement mortar (1 part cement, 1 part clean coarse sand of grade 3mm and down). Store it under the damp jute bags for 24 hours filled by immersion in clean water for 3 days. Remove and wipe out any traces of moisture.

Procedure:

(I) Place the specimen with flat face s horizontal and mortar filled face facing upwards between plates of the testing machine.

(II) Apply load axially at a uniform rate of 14 N/mm² (140 Kg/cm²) per minute till failure occurs and note maximum load at failure.

(III) The load at failure is maximum load at which the specimen fails to produce any further increase in the indicator reading on the testing machine.

2.6 Stabilized Earth Block, Sand Lime bricks and refractory bricks:

The Stabilized Compressed Earth Block (SCEB) Technology offers a cost effective, environmentally sound masonry system for the production of earth block. The product, a stabilized Compressed Earth Block has a wide application in construction for walling, roofing, arched openings. Stabilized Earth Blocks are manufactured by compacting raw material earth mixed with a stabilizer such as cement or lime under a pressure of 20 - 40 kg/cm² using manual soil press called Balram. The basic principal of all the machines is the compaction of raw earth to attain dense, even sized masonry.

Advantage of CEB

Ø Cost effective

Ø Environmentally friendly - conserves agricultural soil and non-renewable fuel

Ø Provides better thermal insulation

Ø Uses local resources

Ø Appealing aesthetics - elegant profile and uniform size

Techno-economic characteristics/ Specifications Dimensional Variation +/-2 mm, Wet compressive strength 20-30 kg/cm^2, Water absorption <15% by weight, Erosion <5% by weight, Expansion on Saturation-Expansion on Saturation, Surface characteristics-No pitting on the surface.

Sand Lime Bricks:

Sand lime bricks are made by mixing sand, fly ash and lime followed by a chemical process during wet mixing. The mix is then molded under pressure forming the brick. These bricks can offer advantages over clay bricks such as:

Ø Their color appearance is grey instead of the regular reddish color.

Ø Their shape is uniform and presents a smoother finish that doesn’t require plastering.

Ø These bricks offer excellent strength as a load-bearing member.

Refractory Brick:

Refractory brick, also known as fire brick, is a type of specialized brick which is designed for use in high heat environments such as kilns and furnaces. Numerous companies manufacture refractory brick in a range of shapes, sizes, and styles, and it can be ordered directly through manufacturers or through companies which supply materials to people who work with high heat processing of materials. High quality refractory brick has a number of traits which make it distinct from other types of brick. The primarily important property of refractory brick is that it can withstand very high temperatures without failing. It also tends to have low thermal conductivity, which is designed to make operating environments safer and more efficient.

Refractory brick can withstand impact from objects inside a high heat environment, and it can contain minor explosions which may occur during the heating process. It may be dense or porous, depending on the design and the intended utility. This brick product is made with specialty clays which can be blended with materials such as magnesia, silicon carbide, alumina, silica, and chromium oxide. Using refractory brick which is not designed for the application can be dangerous, as the bricks may fail, cracking, exploding, or developing other problems during use which could pose a threat to safety in addition to fouling a project.

Some places where refractory brick can appear include: fireplaces, wood stoves, cremation furnaces, ceramic kilns, furnaces and some types of ovens.

2.7 Miscellaneous Clay Products TILES

A tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, or even glass. Tiles are generally used for covering roofs, floors, walls, showers, or other objects such as tabletops. Alternatively, tile can sometimes refer to similar units made from lightweight materials such as wood, and mineral wool, typically used for wall and ceiling. Tiles are often used to form wall and floor coverings. Tiles are most often made from porcelain, fired clay or ceramic with a hard glaze, but other materials are also commonly used, such as glass, metal and stone. Tiling stone is typically marble, onyx, granite or slate. Thinner tiles can be used on walls than on floors, which require thicker, more durable surfaces. The following are the types of tiles:

Tiles, being thinner than bricks, should be carefully handled to avoid any damage. Classification of tiles:

1. Common Tiles: These tiles are of different shapes and sizes and are used for flooring, roofing and paving.

2. Encaustic Tiles: These tiles are used for decorative purposes in floors, walls, roofs and in ceiling.

Based on the purpose of use of tiles:

1. Roofing Tiles

2. Flooring Tiles

3. Wall Tiles

4. Drain Tiles

5. Glazed Earthenware Tiles

Note: Refer Engineering Materials by R.K. Rajput for Complete Materials.

Terracotta:

It is a type of earthenware, is a clay-based unglazed or glazed ceramic, where the fired body is porous. Its uses include vessels (notably flower pots), water and waste water pipes, bricks, and surface embellishment in building construction. The term is also used to refer to items made out of this material and to its natural, brownish orange color, which varies considerably. In archaeology and art history, "terracotta" is often used of objects not made on a potter's wheel, such as figurines, where objects made on the wheel from the same material, possibly even by the same person, are called pottery; the choice of term depending on the type of object rather than the material^.

Earthenware:

Earthenware is a common ceramic material, which is used extensively for pottery tableware and decorative objects. Although body formulations vary between countries and even between individual makers, a generic composition is 25% ball clay, 28% kaolin, 32% quartz and 15% feldspar. Earthenware is one of the oldest materials used in pottery. After firing the body is porous and opaque, and depending on the raw materials used will be colored from white to buff to red. Earthenware is also less strong, less tough and more porous than stoneware, but is less expensive and easier to work. Due to its higher porosity, it must usually be glazed in order to be watertight.

Stoneware:

Mugs, plates, casserole dishes, platters, bowls etc. are made up of stoneware. Many of these things may be made of stoneware. These pieces will either be made in earthenware (low-fired clay) or in stoneware (high- fired clay). Earthenware is white and porous clay that is fired at a low temperature (about 1915 degrees Fahrenheit). (Earthenware is usually called "ceramics" or "ceramic ware".) It is then decorated, glazed with a clear coat and fired. Stoneware is stronger clay that is fired to a high temperature (about 2185 degrees Fahrenheit) and becomes vitreous. It can then be left undecorated or decorated with colored glazes with an optional clear glaze coating and re-fired. Stoneware is clay that when fired to maturity becomes a sturdy, chip resistant material suitable for using in cooking, baking, storing liquids, as serving dishes and to use in the garden. These pieces are meant to be used due to their durability.

Difference between Stoneware and earthenware:

Stoneware	Earthenware (ceramic ware)
Impervious to water (water tight)	Not impervious to water (cannot hold water)
Chip resistant	Chips easily
Color: Buff or terra cotta	Color: white
Feel: textured	Feel: chalky
Look: like pottery	Look: rough white
Looks great undecorated or decorated.	Can only use when decorated.

Can withstand high/low temp.	Cannot withstand high/low temp.
Oven safe	Not oven safe
Suited for household use.	Suited for decorative use

Concrete blocks:

Concrete blocks are also called cement block, and foundation block – is a large rectangular brick used in construction. Concrete blocks are made from cast concrete, i.e. Portland cement and aggregate, usually sand and fine gravel for high-density blocks. Lower density blocks may used industrial wastes as an aggregate. Concrete blocks may be produced with hollow centres to reduce weight or improve insulation. The common size should be 410×200×200 mm and the actual size is usually about ³⁄8 in (9.5 mm) smaller to allow for mortar joints and strength is about 7 MPa to 34 Mpa.

Glazing:

Glazed brick is a type of brick that has a ceramic coating fused to its exterior surface. These bricks are typically fired twice, once for the creation of the brick itself and the second time to fuse the ceramic coating on the brick’s surface. Glazed brick is an attractive, durable option that finds use in interior and exterior constructions.

Advantages of Using Glazed Brick:

Glazed brick has been in use in construction for many years. It is popular because of the several varied advantages it can provide. It is durable, attractive and can provide a unique look to any building. Glazing of brick provides:

Durability: Glazed bricks provide superior durability and strength, which far exceeds that of normal bricks. These bricks last in good condition over the lifespan of most buildings. High degree of resistance to fire is another major asset of glazed bricks. Most of these products have exceptionally good fire ratings, which makes them superior from the safety aspect. It is also safe for the health of the occupants of the building because it does not emit any toxic fumes and does not degenerate with time. The tough satiny finish on glazed

bricks makes them highly impervious to graffiti and vandalism. As a result, they are widely used in business and educational institutions.

Versatility: Glazed bricks match the look of the other existing components of a building, so they are often used in renovation projects or to enhance the look of a building. These bricks are available in many sizes, shapes, colors and finishes such as matte or glossy. This provides every buyer with a choice that matches their requirements. Glazed bricks are tough enough to withstand any climatic condition. They are also better suited to harsh climates that see extremes of temperature, because they are resistant to frost and also remain unaffected by extremely hot temperatures. Freeze and thaw cycles in colder regions may affect other construction materials in a negative way, but glazed bricks remain largely impervious.

Ease of Maintenance: You can easily clean glazed bricks with mild detergent and water. Glazed bricks require minimal maintenance and care, which adds to their popularity as a building material. Glazed bricks have a high degree of resistance to most chemicals. They are also tough and impervious to heavy loads and impact. This makes them ideal choices for high traffic areas, whether in the interior or exterior of a building. Because they are fired at extremely high temperatures, glazed bricks are impervious to color fading. They maintain their aesthetic appeal for a very long time and are also resistant to staining.

Disadvantages of Glazed Brick:

One of the disadvantages of glazed bricks is the extremely high temperature required for processing. The double firing process is also not very good for energy conservation. Glazed bricks are also quite expensive and may not suit the budget of every building project. The heaviness of these bricks requires the building of a very secure foundation that will not be affected by the weight on top.

3 Stone and Aggregate

3.1 Physical Classification of Rock/Stone:

1. Geological Classification

a. Igneous Rock-magma

b. Metamorphic Rock-heat, pressure and chemical

c. Sedimentary Rock-sedimentation

2. Physical Classification of Stone:

a. Stratified Rock

b. Unstratified Rock

c. Foliated Rock

d. Non-Foliated

3. Chemical Classification:

a. Silicious Rock (Silica)

b. Argillacious Rock (Aluminum)

c. Calcareous Rock (Calcium Carbonate)

Physical Classification:

1. Stratified Rock: These rocks show a layered structure in their natural environment. They possesses plane of stratification or cleavage and can be easily split up along these planes. Examples: Sandstones, limestone, slate etc.

2. Unstratified Rock: Rocks which do not have strata and cannot be easily split into thin slabs fall into this category. Their structure may be crystalline or granular. Examples: Granite, Marble etc.

3. Foliated Rock: Certain mineral crystals have a tendency to grow perpendicular to the level of stress or pressure applied to them. In this case the rock will become foliated if a strong one directional force is present during recrystallisation.

4. Non-Foliated Rock: When the pressure applied to a recrystallising rock is uniform or if the mineral crystals do not have distinctive growth patterns, the texture of the metamorphic rock will be non-foliated. Slate, probably the most well known foliated rock, originates from the sedimentary rock Shale. The growth of calcite crystals under high heat and pressure causes Limestone to become the non-foliated rock, Marble. Quartz crystals grow during the metamorphism of Sandstone resulting in the formation of the non-foliated rock, Quartzite.

3.2 Quarrying, Dressing and Seasoning of stone:

Quarrying: A place where exposed surfaces of good quality natural rocks are abundantly available is known as ‘quarry’ and the process of taking out stones from the natural bed is known as ‘quarrying’. For extracting building materials such as dimension stone, construction aggregate, sand and gravel; quarries are generally used. This is done with the help of hand tools like pickaxe, chisels, etc., or with the help of machines. Blasting using explosives is another method used in quarrying.

Stone quarrying: The process of splitting the stones into usable shapes and different sizes for the process of building infrastructures is known as stone quarrying. Stones from quarries have been used in all types of stone creations, and they are used in the process of constructions.

Types of stone quarries: Generally stone quarries are classified into four major categories; they are boulder quarries, surface ledge (outcrop) quarries, commercial deep pit quarries, and subterranean quarries. Different strategies are required for each type of quarry to dig out the stones. Quarries like commercial deep bit quarries just came after the growth of technology in hoisting (lifting) stone.

Stone splitting methods:

Blasting: It is used in commercial stone quarrying and since 1970 it was getting used by farmers to break up boulders in the field. Blasting boulders involves drilling a single hole in the center of the boulder. In 19^th century boulder blast holes are usually 2 inches in diameter and range from 12 to 20 inches.

Plug feather method: The early plug and feather methods involves maximum three holes. The person will drill one, two, or three holes as per boulder; the holes are one inch diameter and two to four inch deep. The shim was kept from hitting the bottom of the holes.

Flat wedge method: It requires different type of cutting tool. The cap chisel was the tool used. It uses to chip the hole instead drilling it out. A hole is wider at top; it is narrow and half inch wide. The size varies and is around 2 ½ inches at the top, 1 ¾ inches on the bottom 2 inches deep. Holes were placed every four inches across the line of intended split.

Dressing of Stone: The stones after being quarried are to be cut into suitable sizes and with suitable surfaces. This process is known as the dressing of stones and it is carried out for the following purposes:

Ø To make the transport from the quarry easy and economical.

Ø To suit the requirements of stone masonry.

Ø To get the desired appearance for the stonework.

Frequently a rock is so stratified that it can be split up into blocks whose faces are so nearly parallel and perpendicular that they may be used with little or no dressing in building a substantial wall with comparatively close joints. On the other hand, an igneous rock such as granite must be dressed to a regular form. The first step in making rectangular blocks from any stone is to decide from its stratification, if any, or its cleavage planes, how the stone may be dressed with the least labor in cutting. The stone is then marked in straight lines with some form of marking chalk, and drafts are cut with a drafting chisel so as to give a rectangle whose four

lines lie all in one plane. The other faces are then dressed off with as great accuracy as is desired, so that they are perpendicular (or parallel) to this plane.

Seasoning of Stone: All stone is better for being exposed in the air until it becomes dry before it is set. This gives a chance for the quarry water to evaporate and in nearly all cases renders the stone harder, and prevents the stone from splitting from the action of the frost.

Many stones, particularly certain varieties of sandstone and limestone, that are quite soft and weak when first quarried acquire considerable hardness and strength after they have been exposed to the air for several months. This hardness is supposed to be caused by the fact that the quarry water contained in the stone holds in solution a certain amount of cementing material, which, as the water evaporates, is deposited between the particles of sand, binding them more firmly together and forming a hard outer crust to the stone, although the inside remains soft, as at first. On this account the stone should be cut soon after it is taken from the quarry and if any carving is to be done it should be done before the stone becomes dry, otherwise the hard crust will be broken off and the carving will be from the soft interior, and hence its durability much lessened.

3.3 Artificial Stone

This series of artificial marble is a high polymer solid material mixed by propyl methacrylate (PMMA), natural mineral hydrated aluminum oxide powder Al(OH)3, and pigment.

Artificial Stone Features:

1) Manufactured from specific polymer blends 2.) Artificial Stone Size:

a) 144" x 30" x 1/2“

b) 120" x 30" x 1/2“

c) 96 "x 30" x 1/2"

3) Extremely durable and easy to maintain and repair.

4) The material is non-porous and naturally resistant to a number of stains and acids

5) The material is solid color throughout

6) Color and pattern go all the way through the countertop

"Made from stone, Better than stone” artificial stone (engineered Stone) is mainly comprised of natural marble, stone meal, shell, glass, and etc. Artificial Stone produced from advanced manufacturing systems, radiation elements are almost completely removed from raw stone materials during the production process. Marbles made with such process are safer and healthier, giving user a peace of mind, a truly green and environmental friendly construction material.

Artificial stone refers to a synthetically created compound that resembles or carries the same properties as natural stone. There are many different types of artificial stone, including synthetic gemstones, stone veneer, cement compounds, and cast stone. Artificial stone has many different uses as a material, from the creation of

costume jewelry to the primary construction material in buildings. One of the earliest types of artificial stone is a ceramic compound known as Coade.

3.4 Classification of Aggregate:

Aggregates: Aggregates are a chemically inert material which when bonded by cement paste, forms concrete. Aggregate influence the strength of concrete to a great extent because they constitute bulk of the total volume of concrete. Aggregates are derived from igneous, sedimentary and metamorphic rocks.

Functions (Advantages) of the Aggregates:

1. It provides concrete to behave like artificial stone.

2. It is cheaper materials than cement.

3. It gives the body to the concrete, reduces shrinkage and effect economy.

4. It provides durability to the concrete.

5. It increases the density of the concrete.

6. It prevents segregation of concrete.

7. It provides 70 to 80% of volume of concrete (i.e. provides bulk of concrete).

8. It increases workability of the concrete.

Qualities (or Requirements) of Ideal (good) Aggregates

Ø It must be of proper shape and of well graded.

Ø It should be free from dust and should resist heat and freezing.

Ø It must be hard and strong enough to bear compressive and normal tensile loads on ordinary concrete.

Ø It must be chemically inert, i.e. should not react with cement or any other aggregate or admixture used for concrete making.

Ø It should possess sufficient hardness to resist scratching and abrasion in the set & hardened concrete.

Ø It should possess sufficient toughness to withstand impact and vibratory loads.

Ø It should be free from impurities, inorganic or organic in nature, which can effect adversely on the quality of concrete.

Ø It should be capable of producing an easily workable plastic mixture on combining with cement, water and other aggregate.

Classification of Aggregates:

1. Classification based on Geological origin.

2. Classification based on Size

3. Classification based on specific gravity or unit weight.

4. Classification based on shape.

1. Classification based on Geological origin.

Under this classification the aggregate may be divided in to followings:

(a) Natural Aggregate: These includes all those types of fine and coarse aggregates that are available in almost ready to use form from natural resources. Examples are sands from riverbeds, pits and beaches and gravel from river banks. Natural aggregates are generally derived from their formation like: Igneous rock, sedimentary rock and metamorphic rock.

(b) Artificial Aggregate (processed aggregate): These are specially manufactured for use in making quality concrete and includes broken pieces of burnt clay, shale etc. The broken bricks of good quality provide a satisfactory aggregate for the mass concrete, but not suitable for RCC work. If the crushing strength is less than 30 – 35 MPa, the brick aggregate is not suitable for water proof construction and for road work as well.

(c) By-product aggregate: This includes the material obtained as waste from some industrial products which are suitable for being used as aggregates. CINDER obtained from burning of coal in locomotives and KILN & SLAG obtained from blast furnaces as scum are best example of this category. Concrete made with blast furnace aggregate will have good fire resisting qualities.

2. Classification based on Size

The size of aggregates used in concrete varies from few centimeters or more to few microns. According to this basis, aggregates are classified as:

(a) Fine aggregate: It is a aggregate most of which passes through 4.75mm I.S. sieve. Sand is generally considered to have a lower size limit of about 0.07mm and is the universally available & commonly used natural fine aggregate. Material between 0.06 mm to 0.002 mm is classified as silt and still smaller particles as clay. The fine aggregate may be of following type-

(i) Natural sand: i.e. fine aggregate resulting from natural disintegration of rock or that which has been deposited by stream or glacial agencies.

(ii) Crushed sandstone: i.e. fine aggregate produced by crushing hard stone.

(iii) Crushed gravel sand: which is produced by crushing natural gravel.

(b) Coarse aggregate: The aggregate must of which retained on 4.75 mm I.S. sieve. Gravel from river beds form the best coarse aggregates in making common concrete. The coarse aggregate may be one of the following types:

(i) Crushed Gravel or stone obtained by crushing of gravel or hard rock.

(ii) Uncrushed gravel or stone resulting from natural disintegration of rock, or

(iii) Partially crushed gravel or stone obtained as a product of the blending of above two types.

The coarse aggregate is described by it’s nominal size, i.e. 40mm, 20mm, 16mm and 12.5mm etc. For example, a grade of nominal size 12.5mm means an aggregate most of which passes the 12.5mm I.S.Sieve.

(c) All-in-aggregate: Sometimes combined aggregates are available in nature consisting different fraction of fine and coarse aggregates, which are known as All-in-aggregate. In such cases there is no need to mix sand and stone chips separately. The all-in-aggregates are not generally used for making high quality concrete.

3. Classification based on Shape

The particle shapes of aggregates influence the properties of fresh concrete more than those of hardened concrete.

1.0 Rounded Aggregate

The aggregate with rounded edge (not spherical) particle (e.g. gravel, sand) has minimum voids ranging from 32 to 33%. It gives minimum ratio of surface area to the volume and hence requires less cement paste to make concrete.

The only disadvantage is that the interlocking between it’s particle is less and hence the development of bond is poor making it unsuitable for high strength concrete and pavements.

2.0 Irregular Aggregate

The aggregate having partly rounded particles and partly other has higher % of voids ranging from 35 to 38%. It requires more cement paste for a given workability. The interlocking between particles, though better than that of obtained with the rounded aggregate, is inadequate for high strength concrete.

3.0 Angular Aggregate

The aggregate with sharp, angular and rough particles (crushed rock) has a maximum % of voids ranging from 38 to 40%. The interlocking between the particles is good, thereby providing a good bond. The aggregate requires more cement paste to make workable concrete of high strength than that required by rounded aggregates. The aggregates are suitable for high strength concrete and pavement subjected to tension.

4.0 Flaky Aggregates (Elongated)

An aggregate is termed as flaky when it’s least dimension (thickness) is less than 3/5^th of it’s mean dimension. The mean dimension of the aggregate is the average of the sieve size through which the particle passes and retained. The particle size is said to be elongated when it’s greatest dimension (length) is greater than 9/5^th of it’s dimension.

4. Classification based on specific gravity or unit weight.

(a) Normal (standard) weight aggregate

The aggregates which have the specific gravity 2.5 to 2.7 are known as Normal weight aggregate. The commonly used aggregate like gravel, crushed rock such as basalt, quartz, sandstone, limestone, brick ballast produces the concrete with unit weight ranging from 23 to 26 kN/m³ and crushing strength at 28 days lies between 15 to 40 MPa. It is used for general RCC and PCC work.

(b) Heavy weight aggregate

The aggregate having Specific gravity varies from 2.8 to 2.9 are known as Heavy weight aggregates. These types of aggregate are generally achieved from magnetite (Fe3O4) and Barytes (BaSO4, rock name). Concrete having unit weight of about 30 to 37 kN/m³ can be produced by using magnetite, barites and scrap iron. This type of aggregate is used to construct radiation shield (Nuclear power plant) and Operation Theater, and also used to produce dense and crack free concrete. The main drawback with this aggregate is that it is difficult to have adequate workability without segration. The compressive strength of these concrete is of the order of 20 to 21 MPa. The cement aggregate ratio varies from 1:5 to 1:9 with water cement ratio in between 05 to 0.65.

The aggregate having unit weight in a range of 1.2gm/cm³ (12 kN/m³) is known as light weight aggregates. These aggregates can be either natural such as diatomite, pumice, volcanic, cinder etc or manufactured such as bloated (Abnormally distended especially by fluids or gas) clay, sintered (forged) fly ash or foamed blast furnace slag. They generally used for the manufacture of structural concrete and masonry blocks for reduction of the self weight of concrete. They can also be used to provide better thermal insulation and to improve fire resistance.

3.5 Gradation of Aggregate:

Sieve Analysis (or Dry Mechanical Analysis) is the method of grading of the construction material (basically Aggregate). It is also called particle size distribution of aggregate. Basically, there are three types of gradation of the aggregates:

Ø Well graded

Ø Uniformly (or poorly) graded and

Ø Gap Graded

For the construction purpose well graded material either for fine aggregate or for coarse aggregate is preferred as it consist almost all size of grains and gives compact or dense concrete. But, poorly graded aggregate consist same size of grains, so it is not considered as a good materials. Whereas gap graded consist the presence of some size of particles.

Procedure:

The sample shall be brought to an air-dry condition before weighing and sieving. This may be achieved either

by drying at room temperature or by heating at a temperature of 100” to 110°C.

Sieve analysis is useful for coarse grained materials which are more than 75 microns in size. The sample of aggregate is sieved through a stack of sieves. The sieve with largest opening is placed on the top of the stack. Downward, the size of the sieve opening reduces progressively.

Analysis of fine aggregate (IS 383 (1970))

Arrangement of sieve size from top to bottom should be in following order: 10.0mm, 4.75mm, 2.36mm, 1.18mm, 600- micron, 300-micron, 150-micron and 75-micron.

Analysis of coarse aggregate (IS 2386-1 (1963))

Arrangement should be like this: 80mm, 63mm, 50mm, 40mm, 31.6mm, 25mm, 20mm, 16mm, 12.5mm, 10mm, 6.3mm and 4.75mm.

Below the stack of sieve a pan is to be placed to collect the particles passing through smallest sieve opening. The sample is placed on the topmost sieve and whole set is to be shaken till each sieve contains constant amount of sample. The retained amount of sample in each sieve is weighed. The cumulative weight and % finer passing each sieve is calculated and plotted against the sieve opening (in log scale) to produce the Grain Size Distribution Curve.

The particle size corresponding to “the % finer than” can be obtained from the gradation curve & denoted as Dp. It is defined as the particle size such that p% of soil are smaller than Dp. For example: in graph shown below, D10 = 0.6mm means that 10% of the total weight of the sample consist of particles

smaller than 0.6mm. The general slope of the grain size distribution curve can be described by the term

“Coefficient of Uniformity (Cu) “

Cu = D60 / D10

A smaller Cu means a steeper curve which is the result of concentration of the particle size in smaller range

(particles are more uniform). The aggregate is said to be “well graded” if

1 < Cc < 3, where Cc is Coefficient of curvature Cu > 4 for gravel/aggregate

Cu > 6 for sand

If aggregate fails one or both of these criteria, it is considered as “Poorly Graded (or, Uniformly Graded).”

The coefficient of curvature (Cc) indicates general shape of the gradation curve and is defined by:

Cc = (D30)² / (D10*D60)

Sample Data and Caluclation:

From above graph, D30= 1.5, D10= 0.6, D60 =2.9

Cc = (D30)² / (D10*D60) = (1.5)² / (0.6*2.9) = 1.29 i.e. 1 < Cc < 3, where Cc is Coefficient of curvature

Cu = D60 / D10= 2.9 / 1.5 = 1.93 < 6 i.e. it indicates concentration of the particle size in smaller range (particles are more uniform)

3.6 Fineness Modulus of Aggregate:

From sieve analysis the particle size distribution in a sample of aggregate is found out. In this connection a term known as “Fineness Modulus” (F.M.) is being used. F.M. is a ready index of coarseness or fineness of the material. Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 80mm to 150 micron and dividing this sum by an arbitrary number 100. Larger the value of F.M. coarser is the material.

It is the proportion of coarse and fine aggregate. The FM is calculated by adding the cumulative percentages by mass retained on each of a specified series of sieves and dividing the sum by 100. The FM for fine aggregate should fall within the range of 2.2 to 3.2. The fineness modulus can be calculated as per the following:

Example :

Sieve analysis is conducted on a sample of aggregate through sieve sizes mounted one over the other in order of size with larger sieve on the top. The weight of material retained on each sieve after shaking is shown in table below. Determine Fineness Modulus (F.M.) of the given sample.

Sieve Size (mm)	25	20	16	12.5	11.2	10	4.75	Pan
Weight retained (gms.)	0.0	179.0	503.0	641.5	326.5	240.5	1322.5	251.5

Solution|

% Retained in designated sieve = {Weight retained in designated sieve ̸ (Total weight i.e. 5000)}×100

% Passing = 100 - % Retained in designated sieve

Fineness modulus of given sample = (cumulative percentages by mass retained i.e 521.24)/100 = 5.21

3.7 Bulking of sand (Fine Aggregate)

The increase in the volume of a given mass of sand (fine aggregate) caused by the presence of water is known as Bulking of sand. The bulking of sand is caused by the films of water which pushes the particle apart. The extent of bulking depends up on the % of moisture present in the sand and it’s fineness.

It has been observed that bulking of sand increases gradually with moisture content up to certain point and then begins to decrease with further addition of water due to merging of films until when the sand is inundated (covered with water). At this stage the bulking is practically zero. Thus, bulking effect will be maximum if water content in sand lies in between 4 to 6%. Above figure shows variation of % bulking with moisture content. The relation shows, fine sand bulks considerably more and the maximum bulking is obtained at higher water content than that of coarse sand. In general, bulking may be to an extent of 30% of original dry volume of sand in the fine sands ( particle size 0.25 mm to 0.15 mm) and 15% in the case of coarse sand (particle size around 2mm). If the sand is measured by volume and no allowance is made for bulking, the mix will be richer than that specified because for given mass moist sand occupies considerably larger volume than that of dry sand of same mass. This results in a mix deficient of sand increases the chances of the Segregation of concrete, and then yield of concrete also will be reduced. Hence, an increase in bulking from 15 to 30% will result in an increase of concrete strength by as much as 14%. If no allowance is made for bulking of sand, the concrete strength may vary (reduce) by as much as 25%.

Determination of bulking of Sand APPARATUES.

250 ml measuring cylinder, weighing balance.

PROCEDURE

(i) Take 500gm (W1) of the aggregate.

(ii) Keep the sample in an oven in a tray at a temperature of 100°C-110° C for 24 ± 0.5 hours.

(iii) Cool the sand in an air tight container and weight it (W2)

Water content of the sample = (W1-W2)x 100/W1

(iv) Take out about 250gm of sand and pour it into a pan.

(v) Add 2% (by weight) of water and mix well.

(vi) Pour the sand sample into a 250 ml measuring cylinder and consolidate by shaking.

(vii) Level the surface and read the volume in ml (Yi).

(viii) Take out the whole quantity of sand and continue the experiment by adding 2% water more each time and note the corresponding volume of sand (Y2, Y3….) until the dump sand volume starts decreasing.

(ix) Beyond this point, add 4% more water each time until the sample become fully saturated.

(x) To the standard sample in the measuring cylinder, add about 50 ml water ore and stir the sample well.

(xi) Note down the surface level of inundated sand (Y ml).

CALCULATIONS

Bulking =(Y1-Y) x100/Y

GRAPH

A graph drawn with % water content along X-mas and % bulking along Y- axis.

From the graph, pick out maximum % of bulking occurred, % of water content at maximum bulking, % of water content When bulking is zero & % of bulking for the initial water content (W) of the sample.

FIELD TEST FOR BULKING OF FINE AGGREGATES AIM

To determine necessary adjustment for the bulking of fine aggregate, in the field.

APPARATUES

250 ml measuring cylinder

PROCEDURE

(I) pour the dump sand in to a 250 ml measuring cylinder up to the 200 ml mark.

(II) Fill the cylinder with water and stir well (sufficient water should be poured to submerge the sand compleately and it can be see that the sand surface is now below its original level)

(III) Take the reading at the sand surface (Y ml)

CALCULATIONS

% of bulking= {(200/Y) - 1] x100

Report the percentage bulking of the sand to the nearest whole number.

3.8 Testing of Coarse Aggregate

3.8.1 Water Absorption Test

This test helps to determine the water absorption of coarse aggregates as per IS: 2386 (Part III) – 1963. For this test a sample not less than 2000g should be used.

Procedure to determine water absorption of Aggregates.

i) The sample should be thoroughly washed to remove finer particles and dust, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22 and 32^oC.

ii) After immersion, the entrapped air should be removed by lifting the basket and allowing it to drop 25 times in 25 seconds. The basket and sample should remain immersed for a period of 24 + ½ hrs afterwards.

iii) The basket and aggregates should then be removed from the water, allowed to drain for a few minutes, after which the aggregates should be gently emptied from the basket on to one of the dry clothes and gently surface-dried with the cloth, transferring it to a second dry cloth when the first would remove no further moisture. The aggregates should be spread on the second cloth and exposed to the atmosphere away from direct sunlight till it appears to be completely surface-dry. The aggregates should be weighed (Weight ‘A’).

iv) The aggregates should then be placed in an oven at a temperature of 100 to 110^oC for 24hrs. It should then

be removed from the oven, cooled and weighed (Weight ‘B’).

Formula used is Water absorption = [(A - B)/B] x 100%.

Three such tests should be done and the individual and mean results should be reported. The limit of water absorption for Fine aggregate should be less then or equal to 5% and that of caorse aggregate should be 1%.

Example of water absorption test:

Observation data of three coarse aggregate sample in laboratory for water absorption capacity are given below. Find the average water absorption capacity of C.A.

No. of bricks	Oven dry weight (gm)	Saturate weight (gm)
I	2404	2409
II	2375	2380
III	2486	2491

3.8.2 Shape Test of Aggregate:

THEORY:

The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. For base course and construction of bituminous and cement concrete types, the presence of flaky and elongated particles are considered undesirable as these cause inherent weakness with possibilities of breaking down under heavy loads. Thus, evaluation of shape of the particles, particularly with reference to flakiness and elongation is necessary.

The Flakiness index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than three- fifths (0.6times) of their mean dimension. This test is not applicable to sizes smaller than 6.3mm.

The Elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than nine-fifths (1.8times) their mean dimension. This test is not applicable for sizes smaller than 6.3mm.

3.8.3 Flakiness index and Elongation Index of Coarse Aggregates

AIM:

i. to determine the elongation index of the given aggregates

ii. to determine the flakiness index of the given aggregates

APPARATUS:

The apparatus for the shape tests consists of the following:

(i) A standard thickness gauge

(ii) A standard length gauge

(iii) IS sieves of sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5,10 and 6.3mm

(iv) A balance of capacity 5kg, readable and accurate up to 1 gm.

PROCEDURE:

i) Sieve the sample through the IS sieves (as specified in the table).

ii) Take a minimum of 200 pieces of each fraction to be tested and weigh them.

iii) In order to separate the flaky materials, gauge each fraction for thickness on a thickness gauge. The width of the slot used should be of the dimensions specified in column (4) of the table for the appropriate size of the material.

iv) Weigh the flaky material passing the gauge to an accuracy of at least 0.1 per cent of the test sample.

v) In order to separate the elongated materials, gauge each fraction for length on a length gauge. The width of the slot used should be of the dimensions specified in column (6) of the table for the appropriate size of the material.

vi) Weigh the elongated material retained on the gauge to an accuracy of at least 0.1 per cent of the test sample.

Size of aggregates		Weight of fraction consisting of at least 200 pieces,g	Thickness gauge size, mm	Weight of aggregates in each fraction passing thickness gauge,mm	Length gauge size, mm	Weight of aggregates in each fraction retained on length gauge, mm
Passing through IS Sieve, mm	Retained on IS Sieve, mm	Weight of fraction consisting of at least 200 pieces,g	Thickness gauge size, mm		Length gauge size, mm
1	2	3	4	5	6	7
63	50	W₁	23.90	X₁	-	-
50	40	W₂	27.00	X₂	81.00	Y₁
40	31.5	W₃	19.50	X₃	58.00	Y₂
31.5	25	W₄	16.95	X₄	-	-
25	20	W₅	13.50	X₅	40.5	Y₃
20	16	W₆	10.80	X₆	32.4	Y₄
16	12.5	W₇	8.55	X₇	25.5	Y₅
12.5	10	W₈	6.75	X₈	20.2	Y₆
10	6.3	W₉	4.89	X₉	14.7	Y₇
Total		W =		X =		Y =

OBSERVATIONS:

Flakiness Index = (X1+ X2+…..) /(W1 + W2 + ….) X 100 Elongation Index= (Y1 + Y2 + …)/(W1 + W2 + …) X 100 RECOMMENDED VALUE:

S. No:	Type of pavement	Maximum limits of flakiness index, %
1	Bituminous carpet	30
2 (i)	Bituminous / Asphaltic concrete	25
(ii)	Bituminous Penetration macadam
(iii)	Bituminous surface dressing (single coat, two coats & precoated)
(iv)	Built up spray grout
3 (i)	Bituminous macadam	15
(ii)	WBM base course and surface course	15

3.8.4 Aggregate Abrasion Value

This test helps to determine the abrasion value of coarse aggregates as per IS: 2386 (Part IV) – 1963. The apparatus used in this test are Los Angles abrasion testing machine, IS Sieve of size – 1.7mm, Abrasive charge – 12 nos. cast iron or steel spheres approximately 48mm dia. and each weighing between 390 and 445g ensuring that the total weight of charge is 5000 +25g and Oven.

Sample Preparation:

The test sample should consist of clean aggregates which has been dried in an oven at 105 to 110°C to a substantially constant weight and should conform to one of the grading shown in the table below:

*Tolerance of ± 12 percent permitted.

Grading	No of Steel balls	Weight of charge in gm
A	12	5000 ± 25
B	11	4584 ±25
C	8	3330 ± 20
D	6	2500 ± 15
E	12	5000 ± 25
F	12	5000 ± 25
G	12	5000 ± 25

Procedure to determine Aggregate Abrasion Value: The test sample and the abrasive charge should be placed in the Los Angles abrasion testing machine and the machine rotated at a speed of 20 to 33 revolutions/minute for 1000 revolutions. At the completion of the test, the material should be discharged and sieved through 1.70mm IS Sieve.

Reporting of Results:

i) The material coarser than 1.70mm IS Sieve should be washed dried in an oven at a temperature of 100 to 110^oC to a constant weight and weighed (Weight ‘B’).

ii) The proportion of loss between weight ‘A’ and weight ‘B’ of the test sample should be expressed as a percentage of the original weight of the test sample. This value should be reported as,

Aggregate abrasion value = (A-B)/B x 100%.

S. No.	Type of Pavement	Max. permissible abrasion value in %
1	Water bound macadam sub base course	60
2	WBM base course with bituminous surfacing	50
3	Bituminous bound macadam	50
4	WBM surfacing course	40
5	Bituminous penetration macadam	40
6	Bituminous surface dressing, cement concrete surface course	35
7	Bituminous concrete surface course	30

3.8.5 Aggregate Impact Value

This test is done to determine the aggregate impact value of coarse aggregates as per IS: 2386 (Part IV) –

1963. The apparatus used for determining aggregate impact value of coarse aggregates is:

Impact testing machine conforming to IS: 2386 (Part IV)- 1963,IS Sieves of sizes – 12.5mm, 10mm and 2.36mm, A cylindrical metal measure of 75mm dia. and 50mm depth, A tamping rod of 10mm circular cross section and 230mm length, rounded at one end and Oven.

Preparation of Sample:

i) The test sample should conform to the following grading:

- Passing through 12.5mm IS Sieve – 100%

- Retention on 10mm IS Sieve – 100%

ii) The sample should be oven-dried for 4hrs. at a temperature of 100 to 110^oC and cooled.

iii) The measure should be about one-third full with the prepared aggregates and tamped with 25 strokes of the tamping rod.

A further similar quantity of aggregates should be added and a further tamping of 25 strokes given. The measure should finally be filled to overflow, tamped 25 times and the surplus aggregates struck off, using a tamping rod as a straight edge. The net weight of the aggregates in the measure should be determined to the nearest gram (Weight ‘A’).

Procedure to determine Aggregate Impact Value;

i) The cup of the impact testing machine should be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by 25 strokes of the tamping rod.

ii) The hammer should be raised to 380mm above the upper surface of the aggregates in the cup and allowed to fall freely onto the aggregates. The test sample should be subjected to a total of 15 such blows, each being delivered at an interval of not less than one second.

Reporting of Results:

i) The sample should be removed and sieved through a 2.36mm IS Sieve. The fraction passing through should be weighed (Weight ‘B’). The fraction retained on the sieve should also be weighed (Weight ‘C’) and if the total weight (B+C) is less than the initial weight (A) by more than one gram, the result should be discarded and a fresh test done.

ii) The ratio of the weight of the fines formed to the total sample weight should be expressed as a percentage.

Aggregate impact value = (B/A) x 100%

Three such tests should be carried out and the mean of the results should be reported.

S.No.	Type of pavement	Value not more than
1.	Wearing Course	30
a)	Bituminous surface dressing
b)	Penetration macadam
c)	Bituminous carpet concrete
d)	Cement concrete
2.	Bitumen bound macadam base course	35
3.	WBM base course with bitumen surfacing	40
4.	Cement concrete base course	45

Aggregate Impact Value Classification

<10% Exceptionally Strong

10 – 20% Strong

20-30% Satisfactory for road surfacing

>35% Weak for road surfacing

3.8.6 Aggregate Crushing Value

This test helps to determine the aggregate crushing value of coarse aggregates as per IS: 2386 (Part IV) –

1963. The apparatus used is cylindrical measure and plunger, Compression testing machine, IS Sieves of sizes

– 12.5mm, 10mm and 2.36mm

Procedure to determine Aggregate Crushing Value:

i) The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110^oC for 3 to 4hrs.

ii) The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod.

iii) The weight of aggregates is measured (Weight ‘A’).

iv) The surface of the aggregates is then leveled and the plunger inserted. The apparatus is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40t load in 10 minutes. After this, the load is released.

v) The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is

weighed (Weight ‘B’).

vi) Three tests should be conducted.

Aggregate crushing value = (B/A) x 100%.

3.8.7 Sodium Sulphate Soundness Test:

Soundness test is a good measure of how resistant an aggregate is to chemical weathering. Soundness test determines the resistance to disintegration of aggregates due to alternate cycles of dry and wet condition. Sample of size 10–14 mm and mass 455 gm for the test was washed with distilled water and oven dried at 105–110°C. A saturated solution of sodium sulphate was produced with the density of 1.32 g/cm³. The test specimen was then subjected to five 48 hours immersion and drying cycles. The sodium sulphate soundness value was calculated as:

SSV = (W1ssv–W2ssv/W1ssv)*100 (%)

Where, W1ssv is the initial weight of the sample and W2ssv is the weight retained on 10 mm after the test.

SSV less than 12% mean the aggregates samples are sound and resistant against chemical weathering and frost susceptibility.

4.1 Clay as a cementing Material:

4 Cement

Properties of the clays include plasticity, shrinkage under firing and under air drying, fineness of grain, color after firing, hardness, cohesion, and capacity of the surface to take decoration. On the basis of such qualities clays are variously divided into classes or groups; products are generally made from mixtures of clays and other substances. The purest clays are the china clays and kaolins. "Ball clay" is a name for a group of plastic, refractory (high-temperature) clays used with other clays to improve their plasticity and to increase their strength. Individual clay particles are always smaller than 0.004 mm. Clays often form colloidal suspensions when immersed in water, but the clay particles flocculate (clump) and settle quickly in saline water. Clays are easily molded into a form that they retain when dry, and they become hard and lose their plasticity when subjected to heat.

Kaolinite is the most important mineral component of common clays. It is formed from all rocks containing felspar mineral ass per following reaction:

2KAlSi3O8 + 2H2O + CO2 = Al2SiO5(OH)4 + K2CO3 + 4SiO2

(Felspar Orthoclase + Carbonic acid = Kaolinite + Pot. Carbonate + Silica colloids)

4.2 Lime

Lime is obtained by burning lime stone, depending upon percentage of calcium carbonate (CaCO3) presence in limestone. It is classified into Class A, B, and C, and they are used for masonry, plastering, mortar, etc. By burning Kankar, shells of sea animals and boulders of limestone from the bank of Old River, lime stone is obtained. Lime is the high-temperature product of the calcinations of limestone. Although limestone deposits are found in every state, only a small portion is pure enough for industrial lime manufacturing.

The basic processes in the production of lime are:

1. quarrying raw limestone;

2. preparing limestone for the kilns by crushing and sizing;

3. calcining limestone;

4. processing the lime further by hydrating;

5. miscellaneous transfer, storage, and handling operations.

Important technical terms

Ø Calcinations

It is the process of heating limestone to redness in contact with air. During calcination process, moisture and carbon dioxide are removed from the limestone and the remaining product is known as Lime; it’s chemical composition is oxide of calcium (CaO).

CaCO3 (Lime Stone) = CaO (Lime) + CO2

Ø Quick Lime

It is obtained by calcining pure limestone is called Quick lime (CaO). It has great affinity for moisture. It is amorphous (i.e. not crystalline)

Ø Slaking

Chemical combination of quick lime with required quantity of water for killing the heat and getting into powder form for use.

CaO (Quick lime) + H2O = Ca(OH)2 (Hydrate of lime)

Sources of Lime

1. Lime stone

2. Kankar found below ground

3. Shells of sea animals

4. White chalk is pure limestone and kankar is an impure limestone

Properties of Lime:

Ø Easily Workable

Ø Provides bonding strength to the masonry

Ø Possesses good plasticity

Ø Offers good resistance to the moisture

Ø Stiffens early

Ø An excellent cementing property

Ø Lime masonry provides durable due to low shrinkage in drying

Uses of Lime:

Ø Used as a matrix for concrete

Ø Used as a binding material

Ø Used for plastering

Ø Used as white washing and base coat for distempers

Ø Used for knotting for timber work before painting

Ø Used to produce artificial stone

Ø Creates the nature of plasticizer mixing with Portland cement

Ø Used as a flux for steel manufacturing

Ø Hydraulic lime is used in underground structures

Ø Used for the manufacturing of paints

Ø Used to stabilize the soil

Classifications of Limes

1. Fat Lime:

It is that lime which has high calcium oxide content and can set and become hard only in the presence of carbon dioxide (from atmosphere). Perfectly white in color.

The fat lime is named as high calcium lime, pure lime, rich lime, or white lime. It is obtained from the pure limestone, shell and coral. It absorbs carbon dioxide when it is left in air, and gets transferred into calcium carbonate. When compared with quick lime, the volume of fat lime gets increased to about 2 – 2.5 times.

Properties of Fat lime

Ø It hardens very slowly.

Ø It is having the high degree of plastic (capacity for being molded or altered).

Ø The color is pure white.

Ø In the presence of air, it tends to set very slowly.

Ø It slakes vigorously (combining with water).

Uses of Fat lime:

Ø It is used in white washing and plastering of walls.

Ø It forms lime mortar with sand, which sets in thin joints.

Ø This type of mortar can be used to apply in thin joints of brickwork and stone work.

2. Hydraulic lime:

Lime containing small quantities of silica, alumina and iron oxide, which are in chemical combination with calcium oxide and can set and become hard even in the absence of CO2 and can set under water.

Hydraulic lime is a variety of lime, a slaked lime used to make lime mortar. It contains small quantity of silica, alumina and iron oxide which are in chemical combination of CaO. Hydraulicityis the ability of lime to set under water. Hydraulic lime is produced by heating, calcining limestone that contains clay and other impurities. Calcium reacts in the kiln with the clay minerals to produce silicates that enable the lime to set without exposure to air. Any unreacted calcium is slaked to calcium hydroxide. Hydraulic lime is used for

providing a faster initial set than ordinary lime in more extreme conditions (including under water). Hydraulic lime is a useful building material for the following reasons:

Ø It has a low elastic modulus.

Ø There is no need for expansion (movement) joints.

Ø It allows buildings to "breathe", and does not trap moisture in the walls.

Ø It has a lower firing temperature than Portland cement, and is thus less polluting.

Ø Stone and brickwork bonded with lime is easier to re-use.

Ø Lime acts sacrificially in that it is weaker and breaks down more readily than the masonry, thus saving weaker stone such as sandstone and limestone from the harmful effects of temperature expansion and mortar freeze.

Ø It is less dense than cement.

Ø Lime re-absorbs the carbon dioxide (CO2) emitted by its calcinations (firing), thus partially offsetting the large amount emitted during its manufacture.

1. Poor lime:

This is one among the classifications of lime. This lime is called as impure lime or lean lime. The properties of poor lime are,

Ø The poor lime consists of 30% clay.

Ø It slakes very slowly. The thin paste is formed along with water.

Ø It never gets dissolved with water and gets frequently changed.

Ø It is use to hardens very slowly.

Ø The binding property is very poor.

4.3 Indian standard classification of lime

CLASS A:

It is an eminently hydraulic lime normally used for structural purposes. It is normally supplied as hydrated lime. CaO = 60-70%, clay 20-30%.

CLASS B: Semi hydraulic lime as the name suggests contain both hydraulic lime and fat lime. It is used for mortar for masonry work. It is supplied both as hydrated or quick lime. CaO = 70%, clay=15-20%.

CLASS C: It is predominantly fat lime for finishing coat in plastering and white washing with suitable admixtures such as Surkhi (Surkhi is finely powdered burnt clay and generally made from slightly underburnt bricks) or any other pozollanic material to produce artificial hydraulic lime. It is supplied both as quick lime and hydrated lime. CaO = 85%, clay = Nill.

CLASS D: It is the lime containing substantial proportions of magnesium oxide and is similar to fat lime. It is used for finishing coat in plastering, white washing etc.

CLASS E: It is Kankar lime generally used for masonary mortar and is supplied as generally as hydrated lime.

4.4 Cement, its composition (Bogue compounds) and properties, Cement manufacturing process

Cement is the material with adhesion and cohesion properties obtained from lime stones capable of bonding mineral fragments into a compact whole. By adding water in cement property of setting increased so called hydraulic cement. Cement is obtained by burning and then grinding the mixture of silica, alumina and iron oxide-bearing materials (Clay).

Classification of Cement:

1. Natural: it can be made from stones containing 20-40% clay along with carbonate of lime and carbonate of magnesia. Brown in color and sets rapidly with water.

2. Artificial: Portland cement or special cement. The paste of cement with water sets and hardness can be achieved. It can be manufactured by processing.

Portland cement: The basic ingredients of Portland cement are Calcareous materials (Limestone or chalk- CaCO3& MgCO3) and argillaceous material (Shale or clay).

Ingredients of Cement:

1. Lime (CaO, 60-67%): Combines with silica from clay forms tricalcium & dicalcium silicate (3CaO.SiO2- C3S & 2CaO.SiO2- C2S) responsible for setting and hardening of cement. Higher amount caused cement unsound and disintegration of cement. Lesser amount cause less strength and set quickly. Right proportion

,ales the cement sound and strong.

2. Silica (SiO2, 17-25%): Responsible to strength of cement due to the formation of dicalcium and tricalcium silicates. Higher amount cause higher strength but takes much time to set.

3. Alumina (Al2O3, 3-8%): Combines with other materials cause quick setting of cement. Act as a flux during burning. Excess of it reduces strength of cement.

4. Iron Oxide (Fe2O3, 0.5-6%): Responsible for the color of cement and also for strength and hardness with other materials.

5. Calcium sulphate (CaSO4, 2%): Responsible for the flash-setting of cement.

6. Magnesia (MgO, 0.1-4%): Responsible for colour and hardness.

7. Sulphur and alkalies (1.7-4.3%): Cause efflorescence (powder in surface) in the cement work.

Manufacturing of Cement:

1. Grinding the raw materials.

2. Mixing the raw material in required proportion.

3. Burning in a kiln at temperature 1300-1500°C-nodular shaped clinker.

4. Cooling of clinker and ground to fine powder.

5. Addition of Gypsum of about 3-5%.

6. Packing-Use the product as a name of Portland cement.

Depending upon mixing and grinding Manufacturing are:

1. Wet Process:

Ø Limestone collected from quarries should first crush to smaller fragments.

Ø Crushed materials are fed to ball or tube mill- mixed with clay with addition of little water –slurry (35- 50% water) - Corrected slurry (tested for chemical composition) is then fed to rotary kiln.

Ø Rotary kiln has the diameter of about 3-8 m and length of 30-200m lined with refractory material.

Ø Slurry moves on hot chains and losses moisture called flakes and then subjecting to move up and down and Fusing process takes place at temperature of about 1100-1500°C. During this process about 20-30% material gets fused and lime, silica and alumina get recombined.

Ø The fused mass turns to nodular form of size about 3-20 mm known as clinker and collected in SILOS and weighs 1100-1300 gm/lt.

Ø Clinker is cooled and Gypsum- 2% (CaSO4.2H2O) is added to prevent from flash- setting of cement- increase initial setting time.

Ø The ball mill and tube mill contain several compartments and produce defined fineness of cement.

Ø The material is then fed to packing unit.

Ø Coal/fuel required is about 350 Kg for 1-ton production.

Fig: Rotary kiln

2. Dry Process:

a. Treatment of raw materials: Crushing, drying, grinding, proportioning and blending (mixing) of Lime stone and clay.

Ø Breaking of raw material to 6-14 mm using crushers.

Ø Rotary drying kiln is used to dry the crushed materials.

Ø Grinding is done in two stages as ball mill and tube mills and stored in SILOS.

Ø
Proportioning and blending the raw materials in different stages with adding low quantity of water- 12%.

Fig: Rotary kiln

b. Burning or Calcinations: Well-proportioned powdered mixture is charged into rotary kiln having 60-90 rph. The greenish black colored glass like lusture material called clinker is prepared in this stage. During this process up to 400°C dehydration takes place initially. Then dissociation of Ca & Mg carbonates proceeds up to 900°C and then C2S, C3S, C3AL, C4AF compound formed up to 1500°C-Clinker.

c. Grinding of the Clinker: Calcined hot clinker is first fed into cooling chamber and then Gypsum is added and mixture is pulverized. Then grinding is done in two stage as coarser grinding and finer grinding.

d. Packing and storage of cement: Placed first into concrete storage tanks-SILOS and packed into high density polyethylene bags, jute and packing cloths of 50 Kg capacity. Coal/Fuel consumption is about 120 Kg for 1-ton production.

Clinker (Bogue Compounds) and its properties

Ø Tricalcium Silicate (3CaO.SiO2-C3S): 45-65%, Very good binding quality, medium rate of reaction, minimum rate of heat liberation. The strength of cement in first 28 days is due to C3S.

Ø Dicalcium Silicate (2CaO.SiO2-C2S): 25-35%, slow rate of hydration reaction, slow hardening, begin hardened after 28 days.

Ø Tricalcium Aluminate (3CaO.Al2O3-C3A): 5-15%, Fast reaction, high heat evolution. Rapid hardening cement. Causes initial setting of cement.

Ø Tetra-Calcium-Alumino-Ferrite (4CaO.Al2O3.Fe2O3-C4AF): 8-18%, slow reaction, poor cementing value, less heat evolution.

Fig: Compressive strength of cement compounds with age.

Most of the strength developing properties of cement are controlled by C3S and C2S (the sum of their percentage varies from 70 to 80%).

High Percentage of C3S and low C2S result:

Ø Rapid hardening

Ø High early strength and high heat generation

Ø Less resistance to chemical attack

Low Percentage of C3S and high C2S result:

Ø Slow hardening

Ø Much more ultimate strength with less heat generation

Ø Greater resistance to chemical attack

4.5 Hydration, Heat of Hydration and gain of strength of cement:

The process by which cement, aggregates and water mix and form a new substance is a chemical process which has its own unique properties and products. The main product of the binding of cement and water is heat, which is given off during the hardening of the concrete. This is known as the heat of hydration. When heat of hydration is taken into consideration while designing and pouring concrete, it can be managed properly during the curing and hardening process. However, if the designers do not allow for the heat, it can cause issues with cracking and possibly even compromise the structural integrity of the concrete. It is extremely important to know about heat of hydration and its effects on concrete from the time it is poured and throughout its lifetime.

Hydration of Cement:

The chemical reaction that take place between cement and water is referred as hydration of cement. When water is added to cement, each of the compounds undergoes hydration and contributes to the final concrete product. Only the calcium silicates contribute to strength. Tricalcium silicate is responsible for most of the early strength (first 7 days). Dicalcium silicate, which reacts more slowly, contributes only to the ultimate strength at later times.

Tricalcium silicate + Water ---> Calcium silicate hydrate + Calcium hydroxide + heat 2Ca3SiO5 + 7H2O ---> 3CaO.2SiO2.4H2O + 3Ca(OH)2 + 173.6kJ

The above diagrams represent the formation of pores as calcium silicate hydrate is formed. Note in diagram

(a) that hydration has not yet occurred and the pores (empty spaces between grains) are filled with water. Diagram (b) represents the beginning of hydration. In diagram (c), the hydration continues. Although empty

spaces still exist, they are filled with water and calcium hydroxide. Diagram (d) shows nearly hardened cement paste. Note that the majority of space is filled with calcium silicate hydrate. That which is not filled with the hardened hydrate is primarily calcium hydroxide solution. The hydration will continue as long as water is present and there are still unhydrated compounds in the cement paste.

Dicalcium silicate also affects the strength of concrete through its hydration. Dicalcium silicate reacts with water in a similar manner compared to tricalcium silicate, but much more slowly. The heat released is less than that by the hydration of tricalcium silicate because the dicalcium silicate is much less reactive. The products from the hydration of dicalcium silicate are the same as those for tricalcium silicate:

Dicalcium silicate + Water--->Calcium silicate hydrate + Calcium hydroxide +heat 2 Ca2SiO4 + 5H2O---> 3 CaO.2SiO2.4H2O + Ca(OH)2 + 58.6 kJ

4.6 Types of Cement (OPC, PPC, RHC, white cement) and their uses:

1. Ordinary Portland Cement (OPC): Commonly used cement, medium rate of strength development and heat generation, resistance toward shrinkage and cracking, less resistance in chemical attack. The OPC was classified into three grades, namely 33 grade, 43 grade and 53 grade depending upon the strength of the cement at 28 days when tested as per IS 4031-1988. If the 28 days strength is not less than 33N/mm2, it is called 33 grade cement, if the strength is not less than 43N/mm2, it is called 43 grade cement, and if the strength is not less than 53 N/mm2, it is called 53 grade cement. But the actual strength obtained by these cements at the factory is much higher than the specifications.

Uses: used in any construction work when there is no exposure to sulphate in the soil or in ground water.

2. Rapid Hardening Cement (RHC): It is also known as high early strength cement. Develops strength rapidly. Rapid hardening cement develops at the age of three days, the same strength as that is expected to develop in OPC at 7 days.

Properties:

· It contains relatively more tricalcium silicate (C3S). This is done by adding greater proportion of limestone in the raw materials compared to that of OPC.

· Higher finer particles (air permeability surface area = 3250 sq. cm/gm) than the OPc. This factor helps quicker and complete hydration of cement particle during setting. The extra fineness, however, may be often the cause of development of cracks. Gives much heat of hydration so not used in mass concrete construction

· Setting time for rapid hardening cements are, however the same as for OPC.

Uses:

Pre-fabricated concrete work, fast removal of formwork, road repair works and cold weather concrete to prevent from frost action.

3. Extra Rapid hardening cement: Inter grinding calcium chloride (max. 2%) with RHC. The normal addition of calcium chloride should not exceed 2 percent by weight of the rapid hardening cement. Whole work (Transport, placed, compacted and finished) within 20 minutes and not stored up to a month. The strength of extra rapid hardening cement is about 25 per cent higher than that of rapid hardening cement at one or two days and 10–20 per cent higher at 7 days.

Uses: Used in cold weather condition due to rapid hardening, quick setting and high heat production, 25 % extra strength than RHC at 1-2 days and 10-20 % at 7 days. Not used in pre-stressed concrete work.

4. Sulphate- resisting cement: Sulphate (Mg) reacts with free calcium hydroxide forms CaSO4 and with hydrate with calcium Aluminate to form calcium sulphoaluminate (Vol. 227%) caused the cracks. C3A Contain – 5% and so 2C3A+C4AF should be within 25 %. Uses: Marine construction, foundation and basements, fabrication of pipes used in marshy region, sewage treatment work concrete.

5. Portland slag Cement: Obtained by mixing Portland cement clinker, gypsum and granulated blast furnace slag in suitable proportions and grinding the mixture to get uniform mixture. It has low heat of hydration, refined grain, resistance to chemical attack. Uses: Mass concrete work.

6. Quick setting Cement: Set quickly and obtained by reducing the amount of gypsum content along with aluminum sulphate during grinding of clinker. This content should be mixed, placed and compacted quickly. It has initial and final setting time of 5 minutes and 30 minutes respectively. Uses: Under Water and running water Construction in which rate of pumping decreasing.

7. Low Heat Cement: Obtained by reducing the C3S (5%) and C3A hydrates quickly and increasing C2S (46%) which hydrates slowly. Less compressive strength. It has initial and final setting time of 1 hr and 10 hr respectively. Uses: Mass concrete work.

8. Portland Pozzolana Cement (PPC): Integration of OPC clinker with siliceous or aluminous material called pozzolanic materials (volcanic ash, burnt clay, fly ash) up to 10-25%.

Advantages:

· Possess higher tensile strength

· Less heat of hydration (i.e. evolves less heat during setting),

· Offer greater resistance to expansion, aggressive water.

· Offers higher resistance to chemical attack and to the action of sea water.

Disadvantages:

· Less compressive strength in early days

Uses:

· Marine and hydraulic structures (mass concrete works) such as dams weirs etc.

· It is also used in sewage work and for laying concrete for water.

9. Air Entraining Cement: Air-Entraining Cement is made by mixing a small amount of an air-entraining agent with ordinary Portland cement clinker at the time of grinding. Air bubbles are entrapped. Air-entraining agents:

Ø Alkali salts of wood resins.

Ø Synthetic detergents of the alkyl-aryl sulphonate type.

Ø Calcium lignosulphate derived from the sulphite process in paper making.

Ø Calcium salts of glues and other proteins obtained in the treatment of animal hides.

These agents in powder, or in liquid forms are added to the extent of 0.025–0.1 per cent by weight of cement clinker. There are other additives including animal and vegetable fats, oil and their acids could be used. Wetting agents, aluminum powder, hydrogen peroxide could also be used.

10. White Cement:

Special type of Portland cement which on use gives a milky or snow-white appearance. White cement is manufactured from pure limestone (Chalk) and clay (i.e. china clay) that are totally free from oxides of iron, manganese and chromium.

For certain applications, usually aesthetic ones, it may be desirable to use a lighter or white Portland cement. while white cement is seen as a luxury product, there are a number of practical applications. ―Remove all the coloring components (Iron, Chromium and Manganese) in Portland cement to make white Portland cement is much easer said than done. The raw materials that are used must be chosen carefully and screened to minimize the presence of coloring oxides, and the production process must be monitored to maintain the lightness and whiteness.

· It dries quickly

· Has superior aesthetic value

Uses:

· Used as mortars for marble and tiles

· Floor finish, plaster work, ornamental work etc.

4.7 Testing of cement (fineness, soundness, consistency, setting time, compressive strength and tensile strength)

1. Fineness test of cement by sieve test:

We need to determine the fineness of cement by dry sieving as per IS: 4031 (Part 1) – 1996.The principle of this is that we determine the proportion of cement whose grain size is larger then specified mesh size.

Apparatus:

The apparatus used are 90μm IS Sieve, Balance capable of weighing 10g to the nearest 10mg, A nylon

or pure bristle brush, preferably with 25 to 40mm, bristle, for cleaning the sieve.

Procedure to determine fineness of cement:

i) Weigh approximately 10g of cement to the nearest 0.01g and place it on the sieve.

ii) Agitate the sieve by swirling, planetary and linear movements, until no more fine material passes through it.

iii) Weigh the residue and express its mass as a percentage R1, of the quantity first placed on the sieve to the nearest 0.1 percent.

iv) Brush all the fine material off the base of the sieve gently.

v) Repeat the whole procedure using a fresh 10g sample to obtain R2.

vi) Then calculate R as the mean of R1 and R2 as a percentage, expressed to the nearest 0.1 percent.

vii) When the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values.

Reporting of Results:

Report the value of R, to the nearest 0.1 percent, as the residue on the 90μm sieve. The allowable value

for OPC is 10% & rapid hardening cement is 5%.

2. SOUNDNESS:

This test is performed to detect the presence of uncombined lime and magnesia in cement. Soundness of cement is determined by Le-Chatelier method as per IS: 4031 (Part 3) – 1988. Apparatus:

Fig: Le Chatelier apparatus

It consists of small brass cylinder as shown in previous Fig. Two indicators with pointed ends are attached to the cylinder on either side of the split. The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 – 1969

Method:

i. The cement paste is prepared; percentage of water is taken as determined in consistency test.

ii. The cylinder is placed on a glass plate and is filled with the cement paste. Covered at top with another glass plate.

iii. The whole assembly is immersed in water at 24˚C to 35˚C for 24 hours.

iv. After 24 hours the distance between the indicators is measured. The mould is immersed in water again and brought to boil in 30 minutes. After boiling for 1 hour the mould is removed, and after cooling, the distance between the tip of indicators is again measured.

v. Increase in this distance represents the expansion of the cement.

vi. According to IS it should not exceed 10 mm for any type of Portland cement.

3. CONSISTENCY TEST OF CEMENT

This test is conducted to determine the percentage of water required for preparing cement paste of standard consistency for other test (e.g. setting time, soundness and compressive strength test)

This test is performed with the help of Vicat’s apparatus as described below.

Fig: Vicat’s apparatus

Vicat’s Apparatus –

Vicat apparatus conforming to IS: 5513 – 1976, Balance, whose permissible variation at a load of 1000g should be +1.0g, Gauging trowel conforming to IS: 10086 – 1982. It consist of a metal frame to which

is attached a movable rod weighing 300 g (along with cap and attachment) and having diameter and length as 10mm and 50 mm respectively. The movable rod is provided with releasing pin to let the rod free and is attached with an indicator to take reading on vertical scale which is graduated from 0 to 40 mm n either direction which gives the penetration. These are the following three attachements:

i. Plunger: used for consistency test

ii. Square needle . . .used for initial setting time test

iii. Annular collar: used for final setting time test

Procedure to determine consistency of cement:

The consistency is measured by the Vicat apparatus by using a 10 mm diameter plunger fitted into the needle holder.

i. Trial paste of cement (300g) and water (30% by weight or 90 g) of cement is mixed and placed in the mould.

ii. Fill the Vicat mould with paste and level it with a trowel.

iii. The plunger is then brought into contact with the top surface of the paste and released.

iv. Under the action of its weight the plunger will penetrate the paste, the depth of penetration depends on the consistency of the paste.

v. Considered to be the standard when the plunger penetrates the paste to a point 5 to 7 mm from the bottom of the mould

vi. The time of gauging should be between 3 to 5 minutes.

vii. The water content of the standard paste is expressed as a percentage by weight of the dry cement. Usual range of value being between 26 and 33 %.

viii. Repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 5 to 7mm. The value lies between 26 to 33%.

SETTING TIME TEST

We need to calculate the initial and final setting time as per IS: 4031 (Part 5) – 1988. To do so we need Vicat apparatus conforming to IS: 5513 – 1976, Balance, whose permissible variation at a load of 1000g should be

+1.0g, Gauging trowel conforming to IS: 10086 – 1982.

A) INITIAL SETTING TIME:

Initial setting time is determined as to give sufficient time for the various operations such as mixing, transportation, placing and compaction of cement mortar or concrete.

i. Cement paste is prepared (as mentioned in the consistency) and is filled in the Vicat mould.

ii. A round or square needle with cross-sectional area of 1 mm² is attached to the moving rod. Lower the needle gently in order to make contact with the surface of the cement paste and release quickly, allowing it to penetrate the test block. Repeat the procedure at regular interval till the needle fails to pierce the test block to a point 5.0 ± 0.5mm measured from the bottom of the mould.

iii. The time period elapsing between the time, water is added to the cement and the time, the needle fails to pierce the test block by 5.0 ± 0.5mm measured from the bottom of the mould, is the initial setting time.

iv. Initial set is expressed as the time elapsed since the mixing water was added to the cement. This time should be about 30 minutes for ordinary cement.

Precautions: Temperature of water and cement paste should be kept within 27±2˚C and at an atmosphere of 90% relative humidity.

B) FINAL SETTING TIME:

Final setting time is determined to find that after laying the mortar or concrete, the hardening should be rapid so that the structure may be used as soon as possible.

i. Cement paste is prepared (as mentioned in the consistency) and is filled in the Vicat mould.

ii. A needle with annular collar (1 mm square needle fitted with a metal attachment hollowed out so as to leave a circular cutting edge 5 mm in diameter and set 0.5 mm behind the top of the needle) is attached to the moving rod of Vicat Apparatus.

iii. Final set is said to have taken place when the needle, gently lowers to the surface of the paste, make an impression on it but the circular cutting edge fails to do so.

iv. Final setting time is reckoned from the moment when mixing water was added to the cement.

v. Final setting time should be about 10n hours for ordinary cement.

According to Indian Standard Specifications:

	Ordinary	Rapid hardening	Low heat
Initial setting time not less than	30 minutes	30 minutes	60 minutes
Final setting time not more than	10 hours	10 hours	10 hours

Physical Characteristic of various types of cement

4. COMPRESSIVE STRENGTH OF CEMENT:

Out of many test applied to the cement, this is the utmost important which gives an idea about all the characteristics of cement. By this single test one can judge that whether cement has been manufactured or not. For cube test two types of specimens either cubes of 7.07 cm X 7.07 cm X 7.07 cm.

This cement mortar (1:3—185g cement, 55g sand and 74g water) is poured in the mould. After 24 hours these moulds are removed and test specimens are put in water for curing. The top surface of these specimens should be made even and smooth. These specimens are tested by compression testing machine after 7 days curing or 28 days curing. Load should be applied gradually till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of cement.

APPARATUS: Compression testing machine, weighing machine

PREPARATION OF CUBE SPECIMENS

I. Clean 9 cube molds of size 7.06 cm and apply oil.

II. The test is performed on 1:3 cement mortar cubes made by gauging 185g of cement, 555g of standard sand and 74g of water.

III. 9 cubes of 7.06cm wide (2.78 inches) are filled with a mortar of composition (1 cement: 3 Standard sand) with water calculated in percentage terms for total dry weight of materials according to formula:

P = (Pn/4) ×3.5 = 0.875Pn

Pn = The quantity of water (expressed in percentage terms of dry weight of cement) which gives a needle penetrates to a depth of (33-35 mm from top of Vicat mould OR 5-7 mm measured from bottom of Vicat mould ) during a normal consistency. Range generally (26- 33%).

IV. The test specimens are stored in moist air (i.e. 90% humidity) for 24 hours and after this period the specimens are marked and removed from the molds and kept submerged in clear freshwater until taken out prior to the test.

V. The temperature of the water must be maintained at 27 ± 2˚C.

VI. As per Indian standard specifications average compressive strength for three cubes should not be less than 11.7 N/mm² and 17.5N/mm² after 2 days and 7 days respectively.

F

i g

Fig: Universal Testing Machine (UTM)

5. TENSILE STRENGTH OF CEMENT:

Ø 1:3 cement mortar with 8% water content of the weight of the solid is mixed and-molded in a standard briquette as shown below.

Ø Curing is done for 24 hrs. at a temperature of 27 ±2°C 24 hrs. at 90 % relative humidity.

Ø Tested in direct tensile testing machine.

Ø Average strength for six briquettes after 3 days and 7 days should not less than 2.0 N/mm² and 2.5 N/mm2

respectively.

25.4 mm

Fig: Briquette for tensile strength test

4.8 Mortar: function and types (mud, lime, cement and gauged)

Mortar is a mechanical mixture in varying proportions of binding materials like cement or lime, clay and fine aggregates. Mortar is termed as a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder such as cement or lime, and water. Mortar can also be used to fix, or point, masonry when the original mortar has washed away.

Function of Mortar:

Ø It binds together and fills the gap between blocks of stone and bricks.

Ø Holds the coarse aggregate together in any concrete

Ø Provides the durable and weather resisting layer between different courses of masonary in the structure

Ø Receives the load and transforms to the foundation

Ø Does pointing and plastering to the structure

Ø Does work for groutin

Mud Mortar:

Clay is the inherent binder of soils which are used in building including for soil- based mortars. Such mortars are generally used with adobe and compressed soil blocks or, sometimes, fired clay brick and soft stone construction. A mud mortar is prepared by simply mixing soil with water until it is in a plastic (workable) state (Required consistency). Once applied, a mud mortar sets quite rapidly on drying without the need for elaborate curing procedures. The beneficial characteristics of mud mortars including good bond to compatible surfaces, relatively high compressive strength and ease of preparation allow them to be used in a range of applications. Life span of this lime is 5 to 15 years.

Uses:

Ø Cob walls: Cob walls are built of mortared mud balls in courses 40 to 80 cm high.

Ø Masonry structures

Ø
Plasters

Lime mortar:

Lime mortar is a type of mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, dating back to the 4th century BC and widely used in Ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to Ancient Egyptian construction. With the introduction of ordinary portland cement (OPC) during the 19th century the use of lime mortar in new constructions gradually declined, largely due to portland's ease of use, quick setting and compressive strength. However the soft, porous properties of lime mortar provide certain advantages when working with softer building materials such as natural stone and terracotta. For this reason, while OPC continues to be commonly used in brick and concrete construction, in the repair of older, stone-built structures and the restoration of historical buildings the use of OPC has largely been discredited.

Cement mortar: Cement mortar is a building compound created by mixing sand and a selection of aggregates with a specified amount of water with cement. The mortar can be used for a number of applications, such as plastering over bricks or other forms of masonry.

Mortar has been used for centuries as a means of adhering bricks or concrete blocks to one another. Cement mortar continues to be used in many different types of construction. Professional building projects often employ mortar as the binder between bricks in walls, fences, and walkways. 1: 8 Cement mortar is nearly twice as strong as 1:3 lime mortar. Uses of cement mortar:

Ø To bind masonry units like stones, bricks and hollow cement blocks.

Ø To give impervious surface to roof slab and walls (plastering).

Ø To give neat finishing to concrete works.

Ø For pointing masonry joints.

Ø For preparing hollow blocks.

Ø Used as DPC

Gauzed Mortar:

Following from the development of ―modern‖ Portland cements, the potential for masonry construction greatly increased. This was attributed to the reliable strength development and much increased rate of strength gain, which enabled construction to be planned and executed far more rapidly. The early limes previously used produced acceptable working properties for the masons. However, the rate of strength gain was low, especially in cold weather conditions. This meant that even a high quality lime, with a good ultimate strength, could prove very problematic for winter usage. Indeed it is probable that the majority of masonry construction proced little, if at all, during the winter months.

The availability of the new Portland cements changed this situation and enabled construction to carry on throughout the year, with the obvious exception of periods of very severe winter weather with heavy precipitations or freezing temperatures. One solution was to use both lime and cement as a binder, with the lime and cement together forming the proportions of one part of binder to two and a half or three of sand. The proportion of Cement, Lime and sand-1:1:6, 1:3:12.

Uses:

Thick brick wall, plastering, thin joints for masonry.

5 Mechanical Behavior

5.1 Types of stress/strains (True and Engineering) and their relationship

Stress:

Internal for of resistance to deformation acting per unit area. Every body offers resistance against any disturbance to its natural state of formation. This internal resistance which the body offers to meet with the load is called stress.

Stress is the force per unit area of a body. If P is the total load acting on the original cross section area A0 then stress is given by relation:

Stress, ∂ = P/A0 (kN/m²)

Types of stress:

Engineering Stress:

When the dimension of the material is taken as the original dimension then the stress is known as engineering stress. It is the ratio of applied load to the original cross-sectional area. If P is the total load acting on the original cross-section area Ao, then stress is given by relation:

Engineering Stress, σeng = P/A0 (kN/m²)

True Stress:

When we apply the load in the material the corresponding dimension of the material changes. The true stress is the ratio of the load at a particular time to the corresponding area.

σTrue=P/Ai

P = Applied load

Ai = Instantaneous cross-section area.

Fig 5.1: Engineering and true stress-strain diagram

Strain:

Strain is the deformation of materials caused by the action of stress. Strain is calculated by first assuming a change between two body states: the beginning state and the final state. Then the difference in placement of two points in this body in those two states expresses the numerical value of strain. Strain therefore expresses itself as a change in size and/or shape.

Given that strain results in the deformation of a body, it can be measured by calculating the change in length of a line or by the change in angle between two lines (where these lines are theoretical constructs within the

deformed body). The change in length of a line is termed the stretch, absolute strain, or extension, and may be written as. Then the (relative) strain, ε, is given by

Where, Ɛ = Strain in measured direction

l = Original length of the material

lo = Current length of the material

The extension is positive if the material has gained length (in tension) and negative if it has reduced length (in compression). Because is always positive, the sign of the strain is always the same as the sign of the extension.

Strain is a dimensionless quantity. It has no units of measure because in the formula the units of length cancel out. Strain is often expressed in dimensions of meters/meter or inches/inch anyway, as a reminder that the number represents a change of length. But the units of length are redundant in such expressions, because they cancel out. When the units of length are left off, strain is seen to be a pure number, which can be expressed as a decimal fraction.

5.2 Stress-Strain Curve of Ductile and Brittle material

a. Ductile Material:

The stress-strain curve characterizes the behavior of the material tested. It is unique for each material and is found by recording the amount of deformation (strain) at distinct intervals of tensile or compressive loading. It is most often plotted using engineering stress and strain measures, because the reference length and cross- sectional area are easily measured. Stress-strain curves generated from tensile test results help engineers to gain insight into the constitutive relationship between stress and strain for a particular material.

In addition to providing quantitative information that is useful for the constitutive relationship, the stress- strain curve can also be used to qualitatively describe and classify the material. Typical regions that can be observed in a stress-strain curve are:

· Elastic region, Yielding

· Strain Hardening

· Necking and Failure

Fig 5.2: Stress strain diagram

A stress-strain curve with each region identified is shown. The curve has been sketched using the assumption that the strain in the specimen is monotonically increasing - no unloading occurs. It should also be emphasized that a lot of variation from what's shown is possible with real materials, and each of the above regions will not always be so clearly delineated. It should be emphasized that the extent of each region in stress-strain space is material dependent, and that not all materials exhibit all of the above regions. We describe each of the regions in more detail in the following sections.

In the Fig 5.2 the initial portion up to proportional limit (σpl) of the stress strain diagram for most materials used in the structures is a straight line. For the initial portion of the diagram the stress (σ) is directly proportional to the strain (ε). Therefore, for a specimen subjected to a uniaxial load we can write: σ ∞ ε

This relationship is known as the Hooke's Law.

Hooke's law describes only the initial linear portion of the Stress-Strain curve for a bar subjected to uniaxial extension. The slope of the stress-strain diagram is called the modulus of elasticity or Young's Modulus.

E= σ/ ε

The elastic limit is the stress beyond which there is permanent deformation of the material. Below the elastic limit all the deformation is recovered when the load is removed. The elastic limit of a solid requires careful definition: For metals, the elastic limit is defined as the 0.2% offset yield strength. This represents the stress at which stress-strain curve for uniaxial tensile loading deviates by a strain of 0.2% from the linear elastic line. It is the stress at which dislocations move large distance through the crystal of the metal.

Beyond Proportional Limit stress increases with less increase in strain upto point Elastic Limit. Strain increases faster than stress at all points on the curve beyond Elastic imit and don't obey Hoole's law. Up to Elastic Limit point, any steel specimen that is loaded and unloaded would return to its original length. This is known as elastic behavior. Elastic Limit is the point after which any continued stress results in permanent, or inelastic, deformation. Beyond Elastic Limit the material starts yielding at which the clear change in strain takes place without increasing the stress. The value of stress corresponding to Yield Limit is known as yield stress. The stress in the material exceeds the yields stress, permanent (plastic) deformation begins to occur. The strain associated with this permanent deformation is called Plastic Strains. Most structures are designed so that the materials used will only undergo elastic deformation. It is necessary to know the stress at which plastic deformation begins. For metal which experience a gradual elastic-plastic transition, the yield stress may be taken to be the point at which the stress-strain curve is no longer linear. A more precise way of determining the limit is to use the stress at a strain of 0.002; this value is known as Yield Strength.

When the material has passed through the yielding point, the stress continues to increasing the strain, but a slower range than the elastic range until the maximum value is reached which is tremens as the ultimate tensile strength. The ultimate tensile stress is about 1.1-3 times the yield stress on ductile materials. The increase in stress upon yield stress is due to material strain hardening. Beyond Ultimate Stress point, the stress decreases and the specimen starts necking. The necking continues until the specimen fractures. The corresponding stress is known as Fracture stress.

This curve is drawn on the assumption that the dimension of the specimen is taken as the original one and is called the Engineering stress-strain curve. Considering the stress and strain at loading instant and dimension are also taken at that instant the corresponding stress-strain diagram drawn is called True stress-strain curve which can be shown in the above diagram.

b. Brittle Material

Brittle materials such as concrete and carbon fiber do not have a yield point, and do not strain-harden which means that the ultimate strength and breaking strength are the same. A most unusual stress strain curve is shown in the figure. Typical brittle materials like glass do not show any plastic deformation but fail while the deformation is elastic. One of the characteristics of a brittle failure is that the two broken parts can be reassembled to produce the same shape as the original component as there will not be a neck formation like in the case of ductile materials. A typical stress strain curve for a brittle material will be linear. Testing of several identical specimens will result in different failure stresses. The curve shown below would be typical of a brittle polymer tested at very slow strain rates at a temperature above its glass transition temperature. Some engineering ceramics show a small amount of ductile behavior at stresses just below that causing failure but the initial part of the curve is a linear.

In brittle materials such as rock, concrete, cast iron, or soil, tensile strength is negligible compared to the compressive strength and it is assumed zero for many engineering applications. Glass fibers have a tensile strength stronger than steel, but bulk glass usually does not. This is due to the Stress Intensity Factor associated with defects in the material. As the size of the sample gets larger, the size of defects also grows. In general, the tensile strength of a rope is always less than the tensile strength of its individual fibers.

Fig 5.3: Typical stress-strain curve for ductile/brittle material

In brittle material the elastic deformation doesn‘t exist. There may not be the significant indication of fracture.

It doesn‘t strain hardened. From the above figure it indicates the fracture stress and there is no neck formation.

5.3 Fracture of metal: ductile and brttle

The failure of material by stress-induced and its separation into two or more parts is known as fracture. Of course, fractures still do occur, and often results in disastrous consequences. A broken axle may cause an automobile accident: a fractured turbine shaft may leave a community without electricity. Basically there are two types of fracture called brittle fracture and ductile fracture which are caused due to tension loading.

1. Brittle Fracture: -

The term “brittle fracture” may be defined as a fracture which takes place by rapid propagation of a crack with negligible deformation. It has been observed that in amorphous materials, the fracture is completely brittle. But in crystalline materials, it occurs after a small deformation. It has been observed that in amorphous materials, the fracture is completely brittle. But in crystalline materials, it occurs after a small deformation.

The final stage in tensile testing separation of the specimen into two pieces. This process of fracture is termed as brittle fracture and involves little prior inelastic deformation: failure occurs abruptly without localized reduction in area. Under uniaxial tension loading, fracture occurs at 90 degrees with the axis of loading. There is no plastic deformation (i.e. there is no necking) and the failure plane has a granular appearance. Polycrystalline materials can fracture in a brittle manner, either along grain boundaries or through the grains.

Griffith‘s theory for brittle fracture OR “Mechanism of Brittle Fracture”

It has been understood that the stress required for the material at which it fractured is only a small fraction of it’s cohesive strength. Therefore, Griffith suggests that the low observed strength were due to the presence of micro-cracks, which acts at the point of concentration

Fig 5.4 Griffith’s elliptical crack model

In order to explain this mechanism of brittle fracture, let us consider a crack of elliptical cross-section in rectangular specimen of glass which is subjected to an axial tensile stress (σ) as shown in above figure. Let, σ

= Applied tensile stress, c = Half crack length

When tensile stress is applied to the specimen, then the stress is distributed throughout the specimen in such a way that the maximum stress occurs at it‘s tips. The expression for maximum stress at the tip of the crack is given by the relation:

σmax= 2σ √(c/r)

Where,

r = radius of the curvature at it ‘s tip.

σ = Tensile stress applied to the specimen c, a = Half-length of crack

We know that before fracture some amount of energy is always stored in the material, which is called Elastic Strain Energy and is given by the following relation:

UE = - (π c² σ²) / E

Where,

UE = Elastic Strain Energy

E = Young ‘s Modulus of Elasticity

A negative sign (-) indicates that the elastic strain energy stored in the material is released as the crack formation takes place. According to Griffith ‘s theory such a crack will propagate when the released elastic strain energy is just sufficient to provide the surface energy for the creation of new surfaces.

If γ be the specific surface energy per unit area in J/m2, then the surface energy due to the presence of crack of length 2c is given by the relation:

US = 2×(2c×1) × γ = 4cγ

The total change in potential energy, resulting from the creation of the crack

Thus, Total change in Potential Energy,

U = UE + US

According to Griffith, such crack will propagate under the effect of a constant applied stress σ (and produce brittle fracture when an incremental surface energy is compensated by a decrease in elastic strain energy. Mathematically,

d (U)/dc = d/dc {(-2π c2 σ2) / E + 4cγ} = 0

-2πcσ2 / E + 4γ = 0 2πcσ2 / E = 4γ

σ = √ (2γE / πc)

Where above expression gives us the stress required to propagate a crack in a brittle material as a function of micro crack. It is valid only for a perfect brittle material like glass.

For the material having γ and E are constant, then

Cc = 2γE / π σ²

σ = √ (2γE / π) × 1/√c

Cc = Critical crack size for fracture for a given stress (σ),

If actual crack size (c) is less than Cc i.e c < Cc, such cracks will not propagate for applied stress (σ)

σ = k × 1/√c

where, k = √ (2γE / π) is Griffith ‘s constant Thus,

σ α 1/√c

Critical crack size (c or a)

Therefore, fracture stress (σ) is inversely proportional to the square root of half crack length (c).

Fig 5.5: Energy in terms of Crack length

Surface energy has a constant value per unit area (or unit length for a unit thickness of body) and is therefore a linear function of (crack length), while the stored strain energy released in crack growth is a function of (crack length)², and is hence parabolic. These changes are indicated in Figure 5.5.

2. Ductile Fracture: - Fracture of the ductile materials occurs in the necked region, which has undergone appreciable plastic deformation. As necking occurs, a tri-axial state of stress develops in the region of necking. This is most popular in round specimens. Failure begins when micro-cracking causing a fibrous surface to develop. This is followed by a rapid fracture oriented at 45o with the axis of loading.

5.4 Hardness: Types (Scratch, indentation and rebound) and its tests (Brinell and rockwell)

The hardness test is a mechanical test for material properties which are used in engineering design, analysis of structures, and materials development. The principal purpose of the hardness test is to determine the suitability of a material for a given application, or the particular treatment to which the material has been subjected. The ease with which the hardness test can be made has made it the most common method of inspection for metals and alloys.

It is the property of the metal by virtue of which it is able to resist abrasion, indentation (or penetration) and scratching by harder bodies. It is measured by the resistance of the metal which it offers to scratching.

The hardness of metal is determined by comparing its hardness with ten standard minerals. The increasing order of their hardness on the Original Moh ‘s scale are shown in table below.

Mohs Hardness Scale
Mineral	Hardness
Talc	1
Gypsum	2
Calcite	3
Fluorite	4
Apatite	5
Orthoclase	6
Quartz	7
Topaz	8
Corundum	9
Diamond	10

The test is conducted by placing a sharp point of one specimen on an unmarked surface of another specimen and attempting to produce a scratch.

Mohs Hardness Testing Procedure

i. Hold one of the standard hardness specimens in the other hand and place a point of that specimen against the selected flat surface of the unknown specimen.

ii. Firmly press the point of the standard specimen against the unknown specimen, and with firm pressure, drag the point of the standard specimen across the surface of the unknown specimen.

iii. Examine the surface of the unknown specimen. With a finger, brush away any mineral fragments or powder that was produced. Did the test produce a scratch? Be careful not to confuse mineral powder or residue with a scratch. A scratch will be a distinct groove cut in the mineral surface, not a mark on the surface that wipes away. Use a hand lens to get a good look at what happened.

iv. Conduct the test a second time to confirm your results.

BRINELL ‘S HARDNESS TEST

Fig 5.6: Brinell principle, Hardness Test

· The Brinell hardness test method consists of indenting the test material (10 mm ± 0.01 mm diameter hardened steel or tungsten carbide ball) subjected to a load of 3000 kg.

· Test Specimen: the thickness of the test specimen should always be more than 8 times the depth of indentation.

· For softer materials the load can be reduced to 1500 kg or 500 kg to avoid excessive indentation.

· The full load is normally applied for 10 to 15 seconds in the case of iron and steel and for at least 30 seconds in the case of other metals. Moreover, the load should be applied gradually and smoothly.

· The diameter of the indentation left in the test material is measured with a low powered microscope.

· The Brinell harness number is calculated by dividing the load applied by the surface area of the indentation. When the indentator (i.e. steel ball) is retracted two diameters of the impression, d1 and d2 , are measured using a microscope with a calibrated graticule and then averaged as shown.

Rockwell ‘s Hardness Test

This test is performed when quick and direct reading desirable. Performed when the materials have hardness, beyond the range of Brinell ‘s Hardness Test and is widely used in industry.

The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration.

When equilibrium has again been reached, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration. The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

There are several considerations for Rockwell hardness test

- Require clean and well positioned indenter and anvil

- The test sample should be clean, dry, smooth and oxide-free surface

- The surface should be flat and perpendicular to the indenter

- Low reading of hardness value might be expected in cylindrical surfaces

- Specimen thickness should be 10 times higher than the depth of the indenter

- The spacing between the indentations should be 3 to 5 times of the indentation diameter

- Loading speed should be standardized.

Fig 5.7: Rockwell hardness testing machine

5.5 Impact Strength and its Test (Charpy and Izod)

Many machine parts are subjected to suddenly applied load called impact blows. It has been observed that a metal may be hard, strong or of high tensile strength, but it may be unsuitable for uses where it is subjected to sharp blows. Th capacity of a metal to withstand such blows without fracture is known as impact resistance or impact strength.

Aim

To know the toughness of the metal under the application of impact load.

To determine the notch sensitivity of a metal under the application of impact load.

In practice Impact test is conducted by several means but all the machines works on the same principle. The very effective impact testing machine by which better impact test results can be found out are given below:

1. Charpy Testing machine (Charpy Test)

2.
Izod Testing Machine (Izod test)

Note: These tests can be performed from the same machine.

1.0 Charpy Test

Specimen for Charpy test is shown in fig. below and in this test the specimen is fixed inside the machine like

simply supported beam having a notch at it’scentre.

Procedure

Specimen is placed over the anvil as shown in above figure. When the pendulum arm is released from known value of angle, then the striking edge (S.E.) or pendulum strikes the specimen with high velocity at the opposite side of the notch. Therefore striking edge may cause fracture for the specimen. After breaking, the pendulum rises on opposite side through the same angle. Neglecting all the mechanical losses during the test, the energy required to fracture this specimen can be found out from the difference of Initial Energy and the Residual (final) energy of Striking Edge. Energy required for Fracture = I.E. – R.E.

Where, I.E. = Initial Energy R.E.= Residual Energy

2.0 Izod Test

This test is conducted by the same machine which is already used for Charpy test, the test calculations for fracture energy is exactly like that of Charpy test. But, in this case the dimension of specimens is different while the striking edge will strike the specimen at the same side of notch. The view of machine set up and specimen size is shown in figure below. In this case the specimen is placed inside the machine like cantilever beam. (Complete Yourself)

6 Metals and Alloys

6.1 Iron: types, manufacturing process, properties and uses Ferrous and Non-ferrous Metals

Ferrous groups of metals are such which contains iron, steel and their alloys whereas non-ferrous metals are such which contains no iron. In Ferrous metal iron is the major constituent. In all jobs ranging from manufacture of primitive type of agricultural implements to advanced types of aircrafts, ferrous metals and their alloys occupy a prominent position. Ferrous and non-ferrous metals are mostly used in engineering field because they confirm to the engineering requirements.

Classification of Ferrous Metals IRON

A. Pig Iron

It is the first or basic form in which iron is prepared as a metal from its ores. When iron ore (i.e. mineral from which metal is extracted) is smelted (to heat and melt) by using Blast-furnace, the initial formation which comes from furnace is called Pig Iron. It is an impure form of iron that is tapped from a blast furnace. Pig iron cannot be used directly in practice but pig iron is used as raw materials for further production of wrought iron and steel.

Composition: It contains iron and varying quantities of other elements amongst which carbon, silicon, manganese, Sulphur and phosphorus are the most important. These may amount to as much as 10% of the weight and 25% of the volume of pig iron.

Manufacture (Formation) of pig iron:

It is manufactured in following stages:

(a) Selection of Ore:

In nature, iron occurs in combined form as oxide, sulphate, carbonate and silicate etc. from such raw resources iron can be extracted economically and are called iron ore. Following are common ores:

1. Hematite (Fe2O3):

Also called Red Iron Ore containing 70% Iron. It has dark brown to red color and is the most common iron ore.

2. Magnetite (Fe3O4):

Black Iron Ore containing 72.4 % of Iron.

3. Siderite (FeCO3)

Spastic Iron Ore containing 48.2 % Iron. Rarely used as iron ore.

Note: Selection of suitable ore is controlled by its occurrence in abundance and its quality (purity).

(b) Dressing of Ore:

The process of reduction in size and removing of impurities to get within required limit is called dressing of ore. This is achieved by passing the ore through a series of crushers and washing mills.

It is done through Blast Furnace. Blast furnace is a cylindrical, shell-like vessel made of steel. It is 15-30 m high and 6-8 m in diameter. The interior of the furnace is lined with refractory bricks. Molten ore gets reduced by reacting carbon monoxide form coke and iron is produced in molten form.

The stack zone: Largest zone extending from top to middle of furnace. The charge coming from above and hot gases from below interact resulting in the dehydration of the ore at 400-600 °C.

The Bosch Zone: It receives the hot air from the blowers through tuyers and the dehydrated charge from the stack zone and reduction of the ore takes place.

3 Fe2O3 + C = 2 Fe3O4 + CO

3 Fe2O3 + 9C = 6 Fe + 9CO Fe3O4 + 4CO = 3Fe + 4CO2

The Hearth Zone: Lowermost part of the furnace. It serves as the receiving pot for the molten iron and slag. Since the molten iron and slag have different densities (Slag is lighter) and drawn from the different holes. The iron is about 95% and other impurities as carbon, Sulphur, silicon, manganese and phosphorous. The slag (called blast furnace slag) is an Alumino-silicate waste product.

400⁰C

600⁰C

1000⁰C

1200⁰C

Hearth

BOSH 1500⁰C

Fig 6.1: Outline of Blast Furnace

Types of Pig Iron:

a) Grey Pig iron: Typical grey colored surface of iron when broken fresh. Soft in character and rich in carbon. Also called foundry pig.

b) White pig iron: Broken surface shows dull white appearance. Also called forge pig iron, as it is hard and brittle.

c) Bessemer Pig iron: Used for manufacture of steel in Bessemer process as this type is practically free from Sulphur and phosphorus.

B) Wrought Iron

Wrought Iron is the purest form of iron containing all impurities below 0.5 %. It was originally produced by slow reduction of the metal from the ore in the forge fire. This reduction process results very impure iron which requires further refining by mechanical working i.e. by hammering or shaping to the form in which it is used. It is very low in carbon content (less than 0.12%) and the iron silicate or slag is distributed through the base metal in fibers which gives it a woody or fibrous appearance when fractured. Wrought Iron is used for some selected engineering applications.

Manufacture of Wrought Iron

It is manufactured from Pig Iron with following two processes:

(i) Puddling Process: It comprises following procedure:

· A small reverberatory furnace called puddling furnace is to be used which has lining of iron oxide bricks.

· Pig iron charge is heated to a 1200⁰C. At this temperature, melted pig iron is oxidized on coming in contact with iron oxide lining.

· The molten charge is regularly stirred or puddle through puddling hole to ensure oxidation with iron oxide lining.

· Carbon is driven off as carbon dioxide and remaining molten charge, containing some slag forms the Wrought Iron. It is squeezed to remove any extra slag.

(ii) Aston Process:

· Pig iron is refined by heating in a Bessemer Converter.

· All impurities is to be removed by directing current of air and molten pig iron is cast into mould.

· A mixture of iron oxide and silica in predetermined proportion is heated separately in a furnace to fusing temperature which forms slag (iron silicate).

· The refined pig iron is put into the mixing machine and hot slag is poured on to it with the help of slag ladle (A spoon-shaped vessel with a long handle; used to transfer liquids).

· Slag is at lower temperature than pig iron. The process mixing slag with iron is called ―shooting‘ and it

results formation of iron-slag balls.

· The iron-slag balls so formed are subjected to pressing machines where extra quantity of slag is squeezed out. The resulting material from pressing machine is Wrought Iron.

Properties and uses:

· It has tensile strength varying between 2500 to 4000 kg/cm². Ultimate compressive strength range between 1500 to 2000 kg/ cm².

· Bluish in color. It is malleable, ductile and tough. It is resistance to corrosion.

· Density of 7.8 gm/cc³ and a melting point of 1500⁰C.

· It shows good resistance to fatigue and sudden shock with ease welding.

Uses:

· For making plates, pipes, tubes. Used in building, marine and railway industries.

(C) Cast Iron:

Cast Iron is produced from remelted pig iron by a process of melting and casting into shape.

Composition: Cast iron contains 2-4 % of carbon. Along with carbon and iron, cast iron also contains Sulphur (S), Silica (Si) and Manganese (Mn). In general cast iron is hard and brittle. It has high compressive strength. Remelting of pig iron is done in a special furnace called cupola.

Manufacture of Cast Iron (Cupola)

· A cupola is an essence a small sized blast furnace of height 5m, diameter 1 m and cylindrical in shape. The cylinder has an inner lining of refractory bricks and is provided with tuyers near bottom for injecting the supply of air blast.

· The raw materials like pig-iron, steel scrap, fuel and fluxes are added from the charge door at the top to a previously heated cupola.

· The air blast is continuously fed through tuyers.

· All impurities of pig iron get oxidized and form a slag that starts floating at the upper layer.

·
The molten cast iron is removed from the lower draw hole and charged directly into mould of desired shapes. These are called Cast Iron.

Properties of cast iron

No generalization of properties of cast iron is possible because properties of cast iron depend on the followings:

1. The composition of cast iron,

2. The rate of cooling and

3. The nature of heat treatment.

Following are the properties which depend on composition:

Carbon: When most of carbon is present as graphite (free carbon), cast iron becomes soft & weak (e.g. grey cast iron). But when carbon presents as cementite, the metal is hard and strong.

Alloying elements:

(a) Nickel:

Nickel cast iron: It contains Nickel in between 0.5 to 3%. Machinability is uniform. Chilled cast iron: Nickel lies in between 3 to 5%. This has high resistance to abrasion. High nickel cast iron: Nickel lies up to 20%. It has resistance to corrosion.

Chromium: Addition of chromium increases hardness and tensile strength of cast iron.

Molybdenum: Addition of this increase the hardness of cast iron.

Heat Treatment: This treatment changes the properties of cast iron to a great extent. White cast iron when subjected to Annealing becomes soft, very ductile and easily machinable.

Impurities: The influence of certain common impurities like phosphorous, sulphur, silicon and manganese is quite pronounced. The presence of carbon increases fluidity makes more softness, Decrease in melting point and increases in casting. The presence of phosphorous increases fluidity and brittleness at ordinary temperature.

Classification of cast iron:

Cast iron is further classified into followings:

· Grey Cast Iron (GCI.)

· White Cast Iron (WCI.)

· Malleable Cast Iron (MCI.)

· Alloy Cast Iron (ACI.)

(1) Gray Cast Iron: It is basically an alloy of carbon and silicon with iron. It contains:

· Carbon (C): 3 to 3.5%

· Silicon (Si): 1.0% to 2.75%

· Sulphur (S): 0.02 to 0.10%

· Manganese (Mn): 0.4% to 1.0%

· Phosphorus (P): 0.15 to 1.0%

· Iron (Fe): Remaining

Properties and uses:

Grey cast iron has low tensile strength, high compressive strength and no ductility. It finds application in making castings, dies, moulds, machine frames and pipes.

(2.) White Cast Iron: - It contains,

· Carbon = 2 to 2.3%,

· Silicon = 0.85 to 1.2%

· Manganese = 0.1 to 0.4%

· Phosphorus = 0.05 to 0.2%

· Sulphur = 0.12% to 0.35%

· Iron (Fe) = Remaining

It is hard, Brittle, high resistance to wear, High Tensile strength, Poor Fluidity.

Uses:

a. Due to high wear resistance used in car wheel and railway brake blocks.

b. Inferior castings due no rusting.

(3.) Molten Cast Iron: - It contained iron=93.5%, Graphite=1.75%, Combined carbon=1.75% and other impurities. It is hard, Brittle, Good fluidity, less tendency to rust, Mixture of GCI & WCI.

Uses: Manhole covers and pipes.

(4.) Malleable cast Iron: - Obtained by long time annealing (Heating, Holding and Transformation) of cast iron. It is soft, Tough and easily machined.

Uses: Brake peddles Tractor springs, hangers, and washing machine parts.

(5) Alloy Cast Iron: When some amount of Nickel (Ni), Chromium (Cr), Molybdenum (Md) etc. are added to the composition of cast iron, the resulting iron which produce is called Alloy Cast Iron. Comparatively it has better properties and strength than other cast irons. It has following properties.

v It has high strength and hardness.

v It has better castability.

v It can be machined and forged easily.

v It possesses resistance to wear and heat.

v It has better corrosion resistance.

Uses:

Alloy cast irons are generally used for making cylinder, internal combustion Engine, Piston rings, pipes etc.

6.2 Steel: composition and types (carbon and alloy steel)

Steel is an alloy of iron (Fe) and Carbon (C). It is produced from pig iron with the help of Bessemer converter. The best thing about steel is that it has very high compressive strength of cast iron and very high tensile strength of wrought iron. As such it is suited for all types of situation as structural materials. By varying carbon content and by suitable heat treatment the properties of steel can be altered from a very soft, workable wire to hard, strong steel for use in tools and machinery where great strength and hardness are required.

Composition: Steel contains maximum up to 2% of carbon (about 1.7%) theoretically. It is tough, strong and ductile.

Basic Oxygen Furnace: In the basic oxygen furnace, the iron is combined with varying amounts of steel scrap (less than 30%) and small amounts of flux. A lance is introduced in the vessel and blows 99% pure oxygen causing a temperature rise to 1700°C. The scrap melts, impurities are oxidized, and the carbon content is reduced by 90%, resulting in liquid steel.

Other processes can follow – secondary steel-making processes – where the properties of steel are determined by the addition of other elements, such as boron, chromium and molybdenum, amongst others, ensuring the exact specification can be met.

Around 0.6 tonnes (600 kg) of coke produces 1 tonne (1000 kg) of steel, which means that around 770 kg of coal are used to produce 1 tonne of steel through this production route.

Basic Oxygen Furnaces currently produce about 70% of the world‘s steel. A further 29% of steel is

produced in Electric Arc Furnaces.

Electric Arc Furnace: The Electric Arc Furnace process, or mini-mill, does not involve ironmaking. It reuses existing steel, avoiding the need for raw materials and their processing. The furnace is charged with steel scrap, it can also include some direct reduced iron (DRI) or pig iron for chemical balance. The EAF operates on the basis of an electrical charge between two electrodes providing the heat for the process. Electric Arc Furnaces do not use coal as a raw material, but many are reliant on the electricity generated by coal-fired power plant elsewhere in the grid. Around 150 kg of coal are used to produce 1 tonne of steel in electric arc furnaces.

Manufacture of Steel

The Bessember Process

Bessemer converter (Isometric Figure) Bessemer converter

The Bessemer converter is an egg or pear shaped vessel supported on trunions in such a way that it can be tilted and even rotated about it‘s horizontal axis. The inner walls of the converter are lined with a refractory material.

Stages

(1) The Bessemer converter is first tilted to a horizontal position. Molten pig iron (raw material) is then fed directly from the furnace. Air is also simultaneously blown into the converter through the tuyers and the converter is straightened up.

(2) Air is kept blowing continuously through the charge. During this process, most of the impurities of the pig iron like Si, C, Mn, S& P gets oxidized on reacting with iron oxide formed as a result of reaction of iron and air. Chemical representation of this change is as follow: 2FeO + Si → 2Fe + SiO2

Due to this reaction maximum amount of heat is produced when amount of Si is more than 1.5 %. FeO + Mn → Fe + MnO

C+ FeO→ CO+ Fe

(3) When oxidation process has progressed sufficiently, predetermined quantities of ferromanganese are added for two purposes:

· It supplies carbon for the steel and

· It deoxidizes any iron oxide left during oxidation of other impurities.

(4) Converter is then tilted into the discharge position and molten metal poured into moulds of special rectangular shapes. The solidified steel is known as INGOT, which is the initial material for preparing other steel shapes.

Some other processes are also available for the manufacture of steel which are as follows:

1. Open Hearth Process

2. The Electric Process

3. Linz-Donawitz Process Have a self study for Knowledge (Refer Book).

4. Duplex Process etc.

6.3 Types of carbon steel and their uses

6.3.1 Plain Carbon Steel

It contains Carbon and iron only in it‘s structure. It contains no alloying elements (such as Si, P, S Mn,

etc.). It has three types:

(a) Low Carbon Steel or (Mild Steel):

It contains:

Carbon (C) : Up to 0.35% Iron (Fe) : Rest

Properties:

It is tough and ductile in nature.

It has better machinability and weldability. It can be forged easily into required form.

It has better tensile strength.

Tensile strength = 400 to 600 MN/m²

Uses:

It is generally used in R.C.C., Locomotives (A wheeled vehicle consisting of a self-propelled engine that is used to draw trains along railway tracks), Sheet metals, Fabricated items, Machine components etc.

(b) Medium Carbon Steel:

It contains:

Carbon (C) : 0.35% to 0.55% Iron (Fe) : Rest

Properties:

It is stronger than mild steel (M.S.)

It has better hardness as compared to mild steel. It is tough and less ductile.

Tensile strength = 550 to 850 MN/m²

It can be machined and forged into required shapes.

Uses:

It is generally used for making Rails, Automobile components, rifle barrels etc.

(c) High Carbon Steel:: Carbon (C) : 0.55% to 1.3% Iron (Fe) : Rest

Properties:

It is hard and strong.

It is less tough as compared to mild steel.

It has better forgeability and castability.

It has better resistance to wear and heat. Tensile strength = 800 to 1050 MN/m²

Uses:

It is generally used for making structural members, Hammers, Gears, Automobile components, Spring, hacksaw blade, carpenter ‘s hand tool, light duty dies etc.

6.4 Properties, advantages and uses of stainless steel, tool steel, brass, aluminium and duraluminum

Alloy Steel

When alloying elements like Silicon (Si), Chromium (Cr), Molybdenum (Mo), Vanadium (V), Cadmium (Cd), Cobalt (Co) etc. are added in small quantities into the composition of plain carbon steel, the resulting steel is called Alloy Steels. Alloy steel possesses superior properties & strength as compared to plain carbon steel.

Alloy steel containing less than 10% of alloying elements are called low alloy steel, where as high alloy steel contains more than 10% of alloying elements. Alloy steels are of following types:

(a) Tool Steel

Steels which are used for tool making are called Tool Steel. Modern technology accepts High Speed Steel (HSS) as better tool steel, thus HSS can be better used for metal cutting. A typical composition of HSS is as given below:

Carbon (C) : 0.65% to 0.75% Tungsten (W) : 18%

Chromium (Cr) : 4% 18/4/1 HSS Vanadium (V) : 1%

Iron (Fe) : Rest

Properties:

It is sufficiently strong, hard and tough. It has better corrosion resistance.

It has better red hardness.

It can be forged and machined into the required tool form easily. Reasonable cost.

It has better wear resistance.

(b) Stainless Steel

It is a rustless or corrosion resistance steel which contains chromium (Cr) and Nickle (Ni) as a allowing elements. A typical stainless steel which is generally used in practice will have following composition:

Carbon (C) : 0.3% to 0.4% Chromium (Cr) : 18% Stainless Steel Nickel (Ni) : 8%

Iron (Fe) : Rest

Properties:

It is strong, hard and tough.

It has excellent corrosion resistance.

It has better formability and machinability.

It has better resistance to heat, ware and abrasion. Cost should be reasonable.

Uses:

In Nuclear power plants.

In Processing Industries (i.e. Farmatutical production) In food Industries. For making surgical equipments.

For making Injection Needle.

For making domestic utensils etc.

(c) Spring Steel:

Steels are which are useful for spring manufacturing process is called Spring Steel. A typical composition of spring steel contains the following:

Carbon (C) : 0.5%

Silicon (Si) : 2% Silco-Manganese Steel Manganese (Mn) : 0.7%

Iron (Fe) : Rest

Properties:

It is strong and tough.

It has high Resilience (An occurrence of rebounding or springing back). It has corrosion resistance.

Itcab be easily made into spring form.

Its cost is higher as compared to other steel which can be used for spring steel.

Uses:

- Manufacturing of all types of springs.

(d) Heat Resistive Steel (HRS):

This alloy steels are used in places where steel objects are subjected to temperature. It contains high carbon % along with C, Cr, Ni, W and Co.

It should have following Properties:

It should have high creep resistance. It should be hard and strong.

It should have low coefficient of expansion. It should have corrosion resistance.

It should have better formability and castability. It should be stable at high temperature.

(e) Die Steel

Steel which are used for die making purpose are called Die steel. Die steel should have the following properties:

It should be sufficiently hard, strong and tough. It should have corrosion resistance.

It should have dimensional stability during operation.

should be of better heat resistance capacity.

It should be friendly to some machining process and manufacturing process.

BRASS:

It includes a group of copper zinc and other alloys having 5-60 % zinc.

Plain Brasses:

1. Commercial Brass: 10% Zinc content, Yellowish in color.

Important Character: Cold worked, good hot working properties, Good welding nature.

Typical Uses: Marine hardware, grill work, forging, rivets, screws and screw wires.

2. Red Brass: 15% Zinc content, Red in color.

Important Character: Strong resistance to corrosion

Typical Uses: Plumbing pipes, Heat exchanger, electrical sockets 3. Low Brass: 20% Zinc content, Gold Red in color.

Important Character: Can easily be soldered and welded.

Typical Uses: Ornamental metal work.

4. Cartridge Brass: 30% Zinc content, Typical Brassy in color. Important Character: Stronger and harder variety of brass Typical Uses: Automotive radiator cores, springs, lamp fixtures.

5. Yellow Brass: 35% Zinc content, Brassy in color.

Important Character: Strongest, resistant to corrosion.

Typical Uses: Plumbing accessories, grill work, springs, screws and chains. 6.

―Muntz Metal‖: 60% Zinc content, Reddish in color.

Important Character: Can be worked hot only, stable under no-corroding water only Typical Uses: Making of condensers, tubes, architectural work, valve stems.

Special Brasses:

1. Naval Brass: Cu=60%, Zn=39%, Tin=01%

Important Character: Hot worked, better resistant to corrosion than MuntzMetal .

Typical Uses: Marine hardware, motor boat shafting, condenser tubes. 2. Admirability Brass: Cu=70%, Zn=29%, Tin=01%

Important Character: Better resistance to corrosion than Cartridge brass.

Typical Uses: best condenser tube material 3. Lead Brass: Cu, Zn, Pb<5% Important Character: Softer than plain brasses, can easily cut by machine tools.

Typical Uses: Plumbing work.

4. Aluminium Brass: Cu, Zn, Al upto 5%

Important Character: Increased hardness, tensile strength, elasticity and ductility.

Typical Uses: Machinery castings, rolled bars

5. Iron Brass: Cu, Zn, Fe upto 3%

Important Character: Higher Strength and better working properties.

Typical Uses: Marine Construction

DURALLUMINIUM:

It is an aluminium alloy which is commonly used in Aero Parts, Automobiles, and Rivets. It contains:

Ø Aluminium (AL) : 95%

Ø Copper (Cu) : 4.5%

Ø Magnesium (Mg) : 0.5% (make them lighter and more easily welded)

Or

Ø Aluminium (AL) : 94%

Ø Copper (Cu) : 4.0%

Ø Magnesium (Mg) : 0.5%

Ø Manganese (Mn) : 0.5%

Ø Iron (Fe) : 0.5%

Ø Silicon(Si) : 0.5%

Properties:

Ø It is tough and ductile and durable.

Ø It has excellent corrosion resistance.

Ø It has excellent machinability.

Ø It has low specific gravity.

Ø It is a good conductor of heat and electricity.

Uses:

Ø Production of rivets, nuts, volts, sheets, tubes

Ø Cables production

Ø Airplanes parts.

Ø Surgical, orthopedic works.

ALUMINIUM:

Aluminum is a very common component of the earth crust (about 8%) but not found independently. The most common ore of aluminum is Bauxite (Al2O3.nH2O).

Uses:

Ø For structural purpose i.e. frame, railing & roofing material.

Ø For making door, window frame, gates, water reservoir & ventilations.

Ø For making aircraft.

Ø For the fabrication of automobiles bodies that need high tolerance.

Ø For making economical conducting materials in electrical industries.

Ø For making aluminum tanks, condensers, heat exchanger, containers etc. in chemical and food processing industry.

Ø For making cooking utensils.

Ø It has considerable resistance to nuclear radiation, so it is used in Nuclear Energy Projects.

Ø For making lithographic plates.

Ø For making sporting goods.

Ø For making road signs and barriers.

Properties of Aluminum:

Ø It is white metal and shows brilliant luster when fresh.

Ø It is lightest material and has sp.gr. of 2.7

Ø It has low melting point of about 650oC.

Ø It has high electrical and thermal conductivities.

Ø It has tensile strength of about 900 kg/cm2.

Ø It has high ductility and so can be transformed into any shape.

Ø It has good castability, so it can be cast in any shape and size by any method.

Ø It has highly resistance to corrosion.

Ø It forms excellent alloy with a number of metals such as cu, Mg, Si, Zn, Mn, Cr

MANUFACTURING PROCESS: Block Diagram

STEP1: Crushing and Grinding: Alumina recovery begins by passing the bauxite through screens to sort it by size. It is then crushed to produce relatively uniformly sized material. The ore is then fed into large grinding mills and mixed

with a caustic soda solution (Sodium Hydroxide) at high temperature and pressure which dissolve oxides of silicon and aluminum. The grinding mill rotates like a huge drum while steel rods - rolling around loose inside the mill - grind the ore to an even finer consistency. The material finally discharged from the mill is called slurry.

The resulting liquor contains a solution of sodium aluminate and undissolved bauxite residues containing Iron, Silicon, and Titanium. These residues - commonly referred to as "red mud" - gradually sink to the bottom of the tank and are removed.

⚫ STEP 2: Digesting: The slurry is pumped to a digester where the chemical reaction to dissolve the

alumina takes place. In the digester the slurry - under 50 pounds per square inch pressure - is heated to 300 °Fahrenheit (145 °Celsius). It remains in the digester under those conditions from 30 minutes to several hours.

More caustic soda is added to dissolve aluminum containing compounds in the slurry. Undesirable compounds either don't dissolve in the caustic soda, or combine with other compounds to create a scale on equipment which must be periodically cleaned. The digestion process produces a sodium aluminate solution. Because all of this takes place in a pressure, the slurry is pumped into a series of "flash tanks" to reduce the pressure and heat before it is transferred into settling tanks

STEP 3: Settling: Settling is achieved primarily by using gravity. Just as a glass of sugar water with fine sand suspended in it will separate out over time, the impurities in the slurry - things like sand and iron and other trace elements that do not dissolve - will eventually settle to the bottom.

The liquor at the top of the tank (which looks like coffee) is now directed through a series of filters. After washing to recover alumina and caustic soda, the remaining red mud is pumped into large storage ponds where it is dried by evaporation.

The alumina in the still warm liquor consists of tiny, suspended crystals. However there are still some very fine, solid impurities that must be removed. Just as coffee filters keep the grounds out of your cup, the filters here work the same way.

The giant-sized filters consist of a series of "leaves" - big cloth filters over steel frames - and remove much of the remaining solids in the liquor. The material caught by the filters is known as a "filter cake" and is washed to remove and caustic soda. The filtered liquor - a sodium aluminate solution - is then cooled and pumped to the "precipitators."

STEP 4: Precipitation: Imagine a tank as tall as a six-story building. Now imagine row after row of those tanks called precipitators. The clear sodium aluminate from the settling and filtering operation is pumped into these precipitators. Fine particles of alumina - called "seed crystals" (alumina hydrate) - are added to start the precipitation of pure alumina particles as the liquor cools. Alumina crystals begin to grow around the seeds, and then settle to the bottom of the tank where they are removed and transferred to "thickening tanks." Finally, it is filtered again then transferred by conveyor to the "Calcination kilns."

STEP 5: Calcination: Calcination is a heating process to remove the chemically combined water from the alumina hydrate. That's why, once the hydrated alumina is calcined, it is referred to as anhydrous alumina. "Anhydrous" means "without water."

From precipitation, the hydrate is filtered and washed to rinse away impurities and remove moisture. A continuous conveyor system delivers the hydrate into the calcining kiln. The calcining kiln is brick-lined inside and gas-fired to a temperature of 2,000 °F or 1,100 °C. It slowly rotates (to make sure the alumina dries evenly) and is mounted on a tilted foundation which allows the alumina to move through it to cooling equipment. (Newer plants use a method called fluid bed calcining where alumina particles are suspended above a screen by hot air and calcined.)

The result is a white powder: pure alumina. The caustic soda is returned to the beginning of the process and used again. At this point, the alumina is ready for conversion into aluminum at a smelter. Alumina is also used in making chemical and ceramics.

Converting Alumina to Aluminum:

Note: Two tons of alumina is required to make one ton of aluminum.

⚫ Smelting: Molten cryolite(a sodium aluminum fluoride mineral) could be used to dissolve alumina and the resulting chemical reaction would produce metallic aluminum. The process takes place in a large Carbon or Graphite lined steel container called a "reduction pot". In most plants, the pots are lined up in long rows, called potlines. The key to the chemical reaction necessary to convert the alumina to metallic aluminum is the running of an electrical current through the cryolite/alumina mixture. The process requires the use of direct current (DC) - not the alternating current (AC) used in homes. The immense amounts of power required to produce aluminum is the reason why aluminum plants are almost always located in areas where affordable electrical power is readily available.

The electrical voltage used in a typical reduction pot is only 5.25 volts, but the amperage is VERY high

- generally in the range of 100,000 to 150,000 amperes or more. The current flows between a carbon anode (positively charged), made of petroleum coke and a cathode (negatively charged), formed by the thick carbon or graphite lining of the pot.

When the electric current passes through the mixture, the carbon of the anode combines with the oxygen in the alumina. The chemical reaction produces metallic aluminum and carbon dioxide. The

molten aluminum settles to the bottom of the pot where it is periodically syphoned off into crucibles while the carbon dioxide - a gas - escapes. Very little cryolite is lost in the process, and the alumina is constantly replenished from storage containers above the reduction pots. The metal is now ready to be forged, turned into alloys, or extruded into the shapes and forms necessary to make appliances, electronics, automobiles, airplanes, cans and hundreds of other familiar, useful items.

Alloys of Aluminum:

Aluminium Alloys are classified as: Aluminium Alloy

§ Cast Alloy

Non-heat treatable Heat Treatable

§ Wrought Alloy

With Mg

With Copper (Duralumin)

With Mg + Si

DURALLUMINIUM

It is an aluminium alloy which is commonly used in Aero Parts, Automobiles, and Rivets etc. It contains:

Aluminium (AL) : 95% Copper (Cu) : 4.5% Magnesium (Mg) : 0.5%

Or

Aluminium (AL) : 94% Copper (Cu) : 4.0% Magnesium (Mg) : 0.5% Manganese (Mn) : 0.5% Iron (Fe) : 0.5% Silicon(Si) : 0.5%

Properties:

It is tough and ductile and durable. It has excellent corrosion resistance. It has excellent machinability.

It has low specific gravity.

It is a good conductor of heat and electricity.

Uses:

- Production of rivets, nuts, volts, sheets, tubes - Cables production

- Airplanes parts.

-Surgical, orthopedic works.

6.5 Different Forms of rolled steel section:

In metalworking, rolling is a metal forming process in which metal stock is passed through a pair of rolls. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallisation temperature, then the process is termed as hot rolling. If the temperature of the metal is below its recrystallisation temperature, the process is termed as cold rolling.

6.6 Reinforcing Steel (TOR and TMT)

TOR Steel) (Twisted Ore Reinforced Steel: The correct technical term for TOR steel is Cold Twisted Deformed (CTD) Steel Reinforcement Bar. These are steel bars with surface deformations formed by twisting the steel after elongation. The elongation process imparts higher yield strength to steel (increases from 250 to say 500MPa) and surface corrugations impart higher bondage with concrete.

TOR steel is one of the best grade of steel used in concrete reinforced. It's a kind of high adherence steel.

TMT Bars: TMT Bars, Thermo mechanically treated bars are high strength deformed steel bars used in reinforced cement concrete (RCC) work manufactured with the help of advancement of technology. TMT bars are latest production in Mild steel bars and have superior properties such as strength, ductility, welding ability, bending ability and highest quality standards at international level. In this process, steel bars get intensive cooling immediately after rolling. When the temperature is suddenly reduced to make surface layer hard, the internal core is hot at the same time. Due to further cooling in atmosphere and heat from the core, the tempering takes place. This process is expected to improve properties such as yield strength, ductility and toughness of TMT bars. With above properties, TMT steel is highly economical and safe for use. TMT steel bars are more corrosion resistant than TOR steel.

Features of TMT Bars

Ø Better ductility and malleability

Ø High yield strength and toughness

Ø More bonding strength

Ø Earthquake resistance

Ø Corrosion resistance

Ø High thermal resistance

Ø Economical and safe in use

Ø No loss in strength at welded joints

Ø Ordinary electrodes can be used for welding the joints

6.7 Corrosion:

Corrosion occurs in the presence of moisture. For example when iron is exposed to moist air, it reacts with oxygen to form rust (Fe2O3.XH2O). The amount of water complexes with the iron oxide (ferric oxide) varies as indicated by the letter "X". The amount of water present also determines the color of rust, which may vary from black to yellow to orange brown. The formation of rust is a very complex process which is thought to begin with the oxidation of iron to ferrous (iron "+2") ions.

Fe > Fe+2 + 2 e-

Both water and oxygen are required for the next sequence of reactions. The iron (+2) ions are further oxidized to form ferric ions (iron "+3") ions.

Fe+2------------------- > Fe+3 + 1 e-

The electrons provided from both oxidation steps are used to reduce oxygen as shown. O2 (g) + 2 H2O + 4e > 4 OH-

The ferric ions then combine with oxygen to form ferric oxide which is then hydrated with varying amounts of water. The overall equation for the rust formation may be written as:

Fe+2(Aq.)+ O2(g)+ 4×2H2O (l)------ > 2Fe2O3.XH2O(S) + 8H+ (Aq.)

The formation of rust can occur at some distance away from the actual pitting or erosion of iron as illustrated below. This is possible because the electrons produced via. the initial oxidation of iron can be conducted through the metal and the iron ions can diffuse through the water layer to another point on the metal surface where oxygen is available. This process results in an electrochemical cell in which iron serves as the anode, oxygen gas as the cathode, and the aqueous solution of ions serving as a "salt bridge" as shown below

Methods of protection from corrosion:

1. Design: Engineering design is a complicated process that includes design for purpose, manufacturability, inspection, and maintenance. One of the considerations often overlooked in designing manufactured products is drainage. The corrosion of the automobile side panel above could have been minimized by providing drainage to allow any water and debris to fall off of the car instead of collecting and causing corrosion from the far side of the panel.

All of the other methods of corrosion control should be considered in the design process. When Ni is added, it prevents the corrosion of iron (Fe) at a pH higher than 12.5 by the formation of a stable oxide. In addition, Ni extends the passive region down to pH 7. Formation of the spinel double oxide (NiFe2O4) on the steel during weathering provides an additional measure of protection from further corrosion.

When Cr is added to Fe, the passive region is extended further than in case of Ni down to pH equal to 4.5, and no ions are formed at high values of pH. Thus, Cr is more effective in corrosion protection of Fe than Ni.

When W is added to Fe, the anion (WO4)-2 is formed at pH as low as 5. This anion, when combined with the Fe cation during early stages of weathering, forms a salt that concentrates in the pores of the rust and acts as a corrosion inhibitor. No ions are formed at high pH values in Fe-W systems. Thus, this alloy is also passive at high pHs.

When Al is added to Fe, a stable FeAl2O4 protective oxide forms in a wide pH region (from 4 to 14).

2. Material Selection:

A. Carbon Steel

Most large metal structures are made from carbon steel-the world's most useful structural material. Carbon steel is inexpensive, readily available in a variety of forms, and can be machined, welded, and formed into many shapes.

This large statue by Pablo Picasso in front of the Chicago city hall is made from a special form of carbon steel known as weathering steel. Weathering steel does not need painting in many boldly exposed environments. Unfortunately, weathering steel has been misused in many circumstances where it could not drain and form a protective rust film. This has given the alloy a mixed reputation in the construction industry.

Where other means of corrosion control are not practical, other alloys can be substituted for carbon steel. This normally doubles or more the material cost for a structure, and other corrosion control methods must be considered before deciding on the use of more expensive alternates to carbon steel. Some forms of carbon steel are subject to special types of corrosion such as hydrogen embrittlement, etc. It is common practice to limit the allowable strength levels of carbon steel to avoid brittle behavior in environments where environmental cracking may occur. High strength bolts cannot be galvanized for the same reason-concerns that they may hydrogen embrittle due to corrosion on the surface. Protective coatings, cathodic protection, and corrosion inhibitors are all extensively used to prolong the life of carbon steel structures and to allow their use in environments such as the Kennedy Space Center where the environment would otherwise be too corrosive for their use.

B.
Stainless Steels

The stainless steel body on this sports car is one example of how stainless steels can be used. The stainless steel is virtually immune to corrosion in this application-at least in comparison to the corrosion that would be experienced by conventional carbon steel or aluminum auto bodies. Stainless steels are a common alternative to carbon steels. There are many kinds of stainless steels, but the most common austenitic stainless steels (300-series stainless steels) are based on the general formula of iron with approximately 18% chromium and 8% nickel. These austenitic stainless steels are frequently immune to general corrosion, but they may experience pitting and crevice corrosion and undergo stress corrosion cracking in some environments.

C. Aluminum

Aluminum alloys are widely used in aerospace applications where their favorable strength-to-weight ratios make them the structural metal of choice. They can have excellent atmospheric corrosion capabilities. Unfortunately, the protective properties of the aluminum oxide films that form on these alloys can break down locally and allow extensive corrosion.

The highway guardrail shown on the right is located near the ocean in Florida. The aluminum alloy maintains a silvery shine except in locations where the passive film has suffered mechanical damage. The wear caused by the rail touching the wooden post at this location destroyed the passive film on the edges of the rail and allowed intergranular corrosion to proceed and cause the exfoliation corrosion shown above. While the corrosion above is very interesting and makes for an interesting web site, it is important to note that the railing is decades old and would have never lasted as long in this location if it were made of carbon steel.

Intergranular corrosion is a major problem on airplanes and other structures made from aluminum alloys. It frequently occurs at bolt and rivet holes or at cutouts where the small grain boundaries perpendicular to the metal surface are exposed.

D. Copper Alloys

Brasses and bronzes are commonly used piping materials, and they are also used for valves and fittings. They are subject to stress corrosion cracking in the presence of ammonia compounds. They also suffer from dealloying and can cause galvanic corrosion when coupled with steel and other structural metals. Most copper alloys are relatively soft and subject to erosion corrosion.

E. Titanium

Titanium is one of the more common metals in nature, but its limited use means that small-scale production operations result in a relatively expensive metal. In the United States it finds extensive use in the aerospace industry. The Japanese make extensive use of titanium in the chemical process industries. There are two general types of titanium alloys-aerospace alloys and corrosion resistant alloys. The crevice corrosion of an aerospace alloy flange in a saltwater application is a classic example of how titanium gets misused

3. Protective coating: The application of enamel is the most common anti-corrosion treatments. They work by providing a barrier of corrosion-resistant material between the damaging environment and the structural material. Painting either by roller or brush is more desirable for tight spaces; spray would

be better for larger coating areas such as steel decks and waterfront applications. Flexible polyurethane coatings, like Durabak-M26 for example, can provide an anti-corrosive seal with a highly durable slip resistant membrane. Painted coatings are relatively easy to apply and have fast drying times although temperature and humidity may cause dry times to vary.

4. Inhibitors and other means of Environmental Alteration: Corrosion inhibitors are chemicals that are added to controlled environments to reduce the corrosivity of these environments. Examples of corrosion inhibitors include the chemicals added to automobile antifreezes to make them less corrosive. Most of the Kennedy Space Center's corrosion inhibitor research involves the effectiveness of inhibitors added to protective coatings.

5. Corrosion allowances: Engineering designers must consider how much metal is necessary to withstand the anticipated load for a given application. Since they can make mistakes, the use of the structure can change, or the structure can be misused, they usually are required to over design the structure by a safety factor that can vary from 20% to over 300%. Once the necessary mechanical load safety factor has been considered, it becomes necessary to consider whether or not a corrosion allowance is necessary to keep the structure safe if it does corrode.

6. Anodization: It is the formation of an oxide layer over the surface of aluminium metal sheet. The oxide layer acts as a protective covering and saves the aluminium underneath from atmospheric corrosion.

7. Controlled permeability formwork: Controlled permeability formwork (CPF) is a method of preventing the corrosion of reinforcement by naturally enhancing the durability of the cover during concrete placement.

8. Cathodic protection: Cathodic protection (CP) is a technique to control the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Cathodic protection systems are most commonly used to protect steel, water, and fuel pipelines and tanks; steel pier piles, ships, and offshore oil platforms.

9. Dipping: This consists of heating the coating metal to its melting point in a dipping tank. The metal to be protected is then dipped into this tank whereby a thin layer of molten material gets deposited over it. Galvanization in which zinc coating is given over iron and steel sheets.

6.8 Heat Treatment of Metals

Basically, heat treatment of metal consists of raising the material some specified temperature. The process is performed to change certain characteristics of metal to make them more suitable for a particular kind of service. It includes: Heating, Holding, and Transformation over time relative to critical temperature. Some of the reasons for heat treatment are:

1. To soften a part so that it can be machined more easily

2. To relieve internal stresses so that a part will maintain its dimensional stability.

3. To refine the grain structure

4. To thoroughly harden a part so that it will be stronger

5. To case harden a part so that it will be more wear resistant

6. To improve mechanical properties: strength, ductility, shock resistance to corrosion

Processes of Heat Treatment:

1. Annealing: The metal is first heated to a temperature in a particular manner and then cooled back to normal temperature. This process make the steel soft, improve machinability, to refine grain size, increase ductility, modify electrical and magnetic property.

a. Full annealing: The steel is heated to temperature above the critical temperature and kept at that temperature at sufficient time and the allowed to cool gradually to the room temperature. Usually done for steel contains 0.3-0.6 % Carbon.

b. Isothermal Annealing: This process involves heating the material above the critical temperature and keeping it at that for a definite time-as is done in the case of full annealing. Then cooling is done rapidly to slightly lower than critical temperature and the cooled gradually to room temperature. This process is suitable for small sections.

c. Sub- critical annealing: This process involves heating the material slightly below the critical temperature and holding at this temperature foe 2-4 Hrs followed by air cooling. This process is suitable for cold sawing and shearing.

2. Normalizing: The heating of steel approximately 4°C above the critical temperature followed by cooling below this range in still air. The process eliminate coarse grain structure during rolling, forging, increase strength of medium carbon steel and improve machinability of low carbon steel, reduce internal stress. This process is applied for casting and forging.

3. Quenching and tempering and hardening: Quenching is the rapid method of cooling of a metal in bath of liquid during heat treatment after holding. The sudden cooling cause the increase in hardness of steel. After quenching the steel is transform and then heated the temperature below critical and hold for air cooling is called tempering. The hardenability of steel is broadly defined as the property which determines the depth and distribution of hardness induced by quenching. Hardenability is a characteristic determined by the following factors as chemical composition, Austenite grain size and structure of alloy before quenching.

7 TIMBER

7.1 Timber: source, types, classification, characteristics, advantages and uses

Timber: Hard solid substance found inside the bark of tree is known as wood. The wood that is used for engineering purpose is called timber. It is important due to

Ø Highly Workable

Ø Resistance against shock

Ø Good looking texture

Ø High salvage value (Residual value)

Total forest area:

The forests of the world are 4.2 billion ha. in extent, covering 27% of the land surface. Fifty percent of the world forest area consists of operable forests (i.e. where commercial cuttings have occurred or could occur). The forest area in developed countries amounts to 45% (about 2 billion hectares (ha)) of the total area, out of which 49% (940 million ha) is operable. In developing countries, forests cover 55% (2.2 billion ha) of the land area, of which 46% (about 1 billion ha) is operable. Predominant in developing countries are the tropical forests of Latin America, South-east Asia and Africa, accounting for 1.7 billion ha.

Types of Tree:

Depending upon the mode of growth

Endogenous tree: - The growth of the tree is inward and outward i.e longitudinally. Stems of such trees are tough enough, too flexible to use for engineering purpose. Bamboo, cane are some examples.

Exogenous tree: - The growth of tree is outward by the addition of one concentric ring in a year (annual rings) by which life of tree can easily found.

1. Conifer or evergreen trees:-Distinct annual rings. Soft wood having light color, light weight, weak strength and pointed leaf. Example- Deodar, pine, chir, kali etc.

2. Deciduous trees:-Same annual rings. Broad leaf, hard wood, heavy weight.

Examples- Sal, shisham, Babul etc.

Characteristics of good timber:

Ø Straight and compacted fiber.

Ø Uniform color

Ø Freshly cut surface should give a sweet smell

Ø Give clear ringing sound when struck

Ø Heavy weight ( relatively- 650 kg/m3)

Ø Free from shakes, knots, cracks and ruptures

Ø Silky luster and smooth surface

Ø No clogging while sawing

Ø Compacted medullary rays

Ø Resistance against fungi, insects and other environmental attack and fire

Ø Durable as well as workable

Advantages:-

Ø Easily available and transported as well. Ø Light in weight but high strength

Ø Easy to handle and planed and joined easily

Ø High salvage value than other materials

Ø Repair, addition and alternation to timber construction is easy

Ø Superior in thermal insulation, sound absorption and electrical resistance

Ø Used as furniture and decorative purpose

Ø Due to strong and flexible used in earthquake resisting purposes.

Ø Used in marine construction due to corrosion resistance behavior

Ø Can resist shock and impact better than concrete

Disadvantages:-

Ø Readily combustible ( can be reduced but not eliminated by treatment)

Ø Less resistance to weathering, fungi, insects and can decayed

Ø Due to humidity it swells and undergoes shrinkage

Ø Length wise strength is three times greater than lateral direction so care should be taken for shear load.

Ø Closely together timber built buildings present conflagration hazards

Ø USES: Timber is used for the following works: For heavy construction works like columns, trusses, piles.

Ø For light construction works like doors, windows, flooring and roofing.

Ø For other permanent works like for railway sleepers, fencing poles, electric poles and gates. Ø For temporary works in construction like scaffolding, centering, shoring and strutting, packing of materials.

For decorative works like showcases and furniture's.

Ø For body works of buses, lorries, trains and boat

Ø For industrial uses like pulps (used in making papers), card boards, wall papers. Ø For making sports goods and musical instruments.

7.2 Growth and Structure of Exogeneous Tree

The basic parts of a tree are the roots, trunk(s), branches, twigs and leaves. Tree stems consist mainly of support and transport tissues (xylem and phloem). Trees may be broadly grouped into exogenous and endogenous trees according to the way in which their stem diameter increases.

Exogenous trees, which comprise the great majority of modern trees (all conifers, and all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark.

Endogenous trees, mainly in the monocotyledons (e.g. palms), grow by addition of new material inwards. As an exogenous tree grows, it creates growth rings.

In temperate climates, these are commonly visible due to changes in the rate of growth with temperature variation over an annual cycle.

Fig: Cross section of an exogenous tree

Annual or growth rings ~ In temperate climates there are two distinctive growth seasons, spring and summer ~ the spring growth is rapid and is shown as a broad band

whereas the hotter, dryer summer growth shows up narrow. In tropical (marine) countries the growth rings are more even and difficult to distinguish.

Bark ~ the outer layer, corklike and provides protection to the tree from knocks and other damage.

Bast~ the inner bark, carries enriched sap from the leaves to the cells where growth takes place.

Pith or medulla ~ the centre of the tree, soft and pithy especially in the branches.

Sapwood ~ new growth carries the raw sap up to the leaves. Usually lighter in colour than the heartwood, especially in softwoods.

Trunk ~ main structure of the tree, produces the commercial timber.

Root structure ~ Absorbs water and minerals from the soil. It is the anchor of the tree.

Cambium ~ layer of living cells between the bast and the sapwood.

Crown ~ the branches and leaves that provide its typical summer shape.

Heartwood ~ mature timber, no longer carries sap, the heart of the tree, provides the strength of the tree. Usually a distinctive darker colour than the sapwood can be shown.

Medulla ray ~ (rays) food storage cells radiating from the medulla ~ provides a decorative feature found in quarter cut timber.

7.3 Defects in Timber:

Types:

1. Natural Defects: Developed during the growths :( Engineering point of view)

a. Knots: Marks the position of growth of branch on the tree. Place of weakness. In cut boards it can be seen as darker appearance.

a. Tight Knot

b. Loose Knot

b. Shakes: Cracks or fissures (Shrinkage on aging, movement caused by wind in the growing tree)— Hearth, Hearth and star, Ring.

a. hearth shake b. hearth & ring shake c. ring shake

c. Cross Grain: fiber in normal tree are usually parallel to the axis of growth but in some timber the fiber makes some angle or slope with the axis called cross grained. Slope= e/L and should be allowable (8.3% or 1 in 12).

d. Rind galls: Overgrowths of timber in some parts of tree is called rind galls.

2. Artificial Defects: Develops after its felling and conversion to different sizes.

a. Wane: Absence of wood in corners of piece of lumber.

b. Blue Stain: Discoloration that penetrates the wood fiber.

c. Machine burn: darkness due to overheating by machine knives.

d. Pitch: An accumulation of resinous material on the surface or pockets below the surface of timbe

e. Wormholes: Small holes in the wood caused by insects and beetles.

f. Bow: A curve along the face of a board that usually runs from end to end.

g. Checking: A crack in the wood structure of a piece, usually running lengthwise. Checks are usually restricted to the end of a board and do not penetrate as far as the opposite side of a piece.

h. Split: A longitudinal separation of the fibers which extends to the opposite face of a piece of sawn timber

i. Twist: Warping in lumber where the ends twist in opposite directions.

7.4 Seasoning of Timber: air, water, kiln, chemical, electrical and boiling

Normally about 45 % free water contained in Timber. Seasoning is lowering the moisture content upto 15- 30% (Generally).

Objective of seasoning:

Ø Reduction in weight:

Ø Increase in Strength :

Ø Improvement in Workability:

Ø Freedom from Shrinkage defects, warp and split:

Ø Longer life and durability-safe from attack of fungi and insects:

Ø To maintain the shape and size constant

Ø To make fit for painting and gluing

1. To reduce or eliminate attack by decay. Wood that is dried below 20 percent moisture content is not susceptible to decay.

2. To reduce the weight. The weight of lumber will be reduced by 35 percent or more by removing most of the water in the wood.

3. To increase the strength. As wood dries, the stiffness, hardness and strength of the wood increases. Most species of wood increase their strength characteristics by 50 percent or more during the process of drying to 15 percent moisture content.

Types:

1. Natural Seasoning: Air Seasoning& water Seasoning

2. Artificial Seasoning: Kiln Seasoning, Chemical Seasoning, Electrical Seasoning, Boiling Seasoning

Air Drying:

Piling lumber for air drying

1. Stack Ground: Levelled, free from debris, dry land and at least few cm above general GL.

2. Stack Pillars: Constructed at regular intervals of bricks, concrete, masonary and 50 cm above GL.

3. Stack Propers: Not exceeding 1.5 m.

The traditional method of seasoning timber was to stack it in air and let the heat of the atmosphere and the natural air movement around the stacked timber removes the moisture. The basic principle is to stack the timber so that plenty of air can circulate around each piece. The timber is stacked with wide spaces between each piece horizontally, and with strips of wood between each layer ensuring that there is a vertical separation too.

Drying time: In warm weather (April through October), 1-inch (2.54 cm) lumber can be dried to 15 or 20 percent moisture content in 45 to 60 days (2-inch lumber in 60 to 90 days). In the winter months, lumber will require twice as long to dry. Lumber at 15 percent to 20 percent moisture content is adequate for building unheated structures such as garages or barns. If the wood is to be used inside a heated structure, further drying in a commercial kiln is necessary (6 percent to 8 percent moisture content for indoor use). Lumber Size: (19 mm × 38 mm-(184 mm × 184 mm)-24 Ft Long.

Water Seasoning: Wood log are placed in running water so that the sap are filled by water. The longer ends of logs being kept pointing up-stream. These processes also reduce the warping at cut length. By this process the sap, sugar and gum should be washed out by filling water which would be replaced by drying in open place.

Kiln Seasoning:

Ø Forced air circulation by using large fans, blowers, etc.

Ø
Heat of some form provided by piped steam. Ø Humidity control provided by steam jets.

Kilns are usually divided into two classes:

1. Progressive

2. Compartmental

1. Progressive Seasoning: In the progressive kiln, timber enters at one end and moves progressively through the kiln much as a car moves through a tunnel. Temperature and humidity differentials are maintained throughout the length of the kiln so that the lumber charge is progressively dried as it moves from one end to the other. A progressive kiln has the stack on trolleys that ‘progressively’ travel through chambers that change the conditions as it travels through the varying atmospheres.

2. Compartmental Seasoning: A compartmental kiln is a single enclosed container or building, etc. The timber is stacked as described above and the whole stack is seasoned using a programme of settings until the whole stack is reduced to the MC required. Compartment kilns differ from progressive kilns in that the timber is loaded into the kiln and remains in place throughout the drying process. Compartment kilns are usually smaller than progressive kilns, and because of their construction the temperature and humidity conditions within them can be closely controlled.

Chemical Seasoning: Seasoned using chemical solution like sodium chloride, sodium nitrate to prevent from cracking.

4. Seasoning by Boiling: Boiling up to 4-5 hours for washed out sap, gum and sugar.

5. Electrical Seasoning: Fresh timber is Good conductor of Electricity and high electricity passed through the timber log and hence heat is generated and moisture is reduced. This method is employed in plywood manufacturing process.

7.5 Preservation of Timber:

Preservation of timber means protecting timber from fungi and insects attack so that its life is increased. Timber is to be seasoned well before application of preservatives. The following are the widely used preservatives:

1. Tar: Hot coal tar is applied to timber with brush. The coating of tar protects the timber from the attack of fungi and insects. It is a cheapest way of protecting timber. The main disadvantage of this method of preservation is that appearance is not good after tar is applied it is not possible to apply other attractive paints. Hence tarring is made only for the unimportant structures like fence poles.

2. Paints: Two to three coats of oil paints are applied on clean surface of wood. The paint protects the timber from moisture. The paint is to be applied from time to time. Paint improves the appearance of the timber. Solignum paint is a special paint which protects the timber from the attack of termites.

4. Chemical salt: These are the preservatives made by dissolving salts in water. The salts used are copper sulphate, magnesium chloride, zinc chloride and sodium fluoride. After treating the timber with these chemical salt paints can be applied to get good appearance.

5. Creosote: Creosote oil (polycyclic aromatic hydrocarbons, phenol, cresols) is obtained by distillation of coal tar. The seasoned timber is kept in an air tight chamber and air is exhausted. Then creosote oil is pumped into the chamber at a pressure of 0.8 to 1.0 N/mm2 and the temperature of 50°C. After 1 to 2 hours timber is taken out of the chamber.

6. ASCO: This preservative is developed by the Forest Research Institute, Dehradun. It consists of 1 part by weight of hydrated arsenic pentoxide (As2O5.2H2O), 3 parts by weight of copper sulphate (CuSO4 5H2O) and 4 parts by weight of potassium dichromate (K2Cr2O7) or sodium dichromate (Na2Cr2O7 2H2O).This preservative is available in powder form. By mixing six parts of this powder with 100 parts of water, the solution is prepared. The solution is then sprayed over the surface of timber. This treatment prevents attack from termites (social insect). The surface may be painted to get desired appearance.

7.6 Properties and Uses of Bamboo:

Bamboo is a trendy star of the eco-friendly construction movement, with a wide variety of flooring, furniture and other items being manufactured with the strong, fast-growing grass. Bamboo is one of the fastest- growing plants on Earth, with reported growth rates of 100 cm (39 in) in 24 hours. However, the growth rate is dependent on local soil and climatic conditions, as well as species, and a more typical growth rate for many

commonly cultivated bamboos in temperate climates is in the range of 3–10 centimeters (1.2–3.9 in) per day during the growing period. Bamboo, like true wood, is a natural composite material with high strength-to- weight ratio useful for structures.

Uses:

1. Application in buildings - bamboo housing: Bamboo has also long been used as scaffolding; the practice has been banned in China for buildings over six storeys, but is still in continuous use for skyscrapers in Hong Kong. In the Philippines, the nipa hut is a fairly typical example of the most basic sort of housing where bamboo is used; the walls are split and woven bamboo, and bamboo slats and poles may be used as its support. In Japanese architecture, bamboo is used primarily as a supplemental and/or decorative element in buildings such as fencing, fountains, grates and gutters.

2. Structural reinforcement: These days the research is doing on the application of bamboo as a reinforcement in concrete structures as a similar manner of steel reinforcement. The primary data indicates that bamboo does have the necessary strength to fulfil this function, but untreated bamboo will swell from the absorption of water from the concrete, causing it to crack. Several procedures must be followed to overcome this shortcoming.

3. Panel Products: There is a wide variety of products which can be referenced in manufacturers

‘websites and brochures that contain product data, design details, and information on handling and finishing.

Panel products consist of processed wood

material bound together to form sheets. Their properties and performance are closely related to the type of particles, the type of glue or binder used and how they are manufactured.

4. Geo-technical applications: The bamboo is used to stabilize soil and soil mass movement. It can also be used for the construction of pile in the foundation. A seagoing bamboo raft of Taiwan, somewhere around 40 feet long. A raft is any flat structure for support or transportation over water.

5. Hydraulic applications: The bamboo is used to divert the flow of water in the river. It can also be used to control the scouring in meandering portion of river.

6. Erosion Control Bio Engineering: Bamboo is used as a bio-engineering plant for the erosion control. The US Department of Agriculture apparently studied bamboo as an erosion control plant and found it very successful.

7. Boat building: TUBS MARINE of Angeles City, Philippines, has built hybrid (with steel) bamboo boats and bamboo fishing sleds. This indicates that bamboo is used for the construction of boat.

8. Textiles: Since the fibers of bamboo are very short (less than 3 mm), they are impossible to transform into yarn in a natural process.[29] The usual process by which textiles labeled as being made of bamboo are produced uses only rayon made from the fibers with heavy employment of chemicals. To accomplish this, the fibers are broken down with chemicals and extruded through mechanical spinnerets; the chemicals include lye, carbon disulfide and strong acids.

9. Paper: Bamboo fiber has been used to make paper in China since early times. A high-quality, handmade paper is still produced in small quantities. Coarse bamboo paper is still used to make spirit money in many Chinese communities.

10. Musical instruments/ Sporting goods: Bamboo musical entrustments and sporting goods are produced these days.

Properties of Bamboo:

Bamboo is a renewable resource due to its short growth time requirement. It only takes about four years from planting to harvest time to prepare it for flooring applications. This flooring also has the added benefit of being highly resistant to moisture absorption. Therefore, if humidity is an issue, bamboo flooring offers a material which will remain true in shape.

Bamboo is a typical natural composite material, which is longitudinally reinforced by strong fibers. The fibers are distributed densely in the outer surface region, and sparsely in the inner surface region, and their volume fraction changes with respect to radius. The structure of bamboo has been characterized by tensile tests and its mechanical properties have been related to its structure. Bamboo is a very complex material and many things affect it including: 1) Direction,

2) Moisture content (MC %),

3) Diameter,

4) Wall thickness,

5) Distance to node

6) Height,

7) Age, and

8) Species.

These are further explained below.

1) Because bamboo grains are aligned parallel in the axial (vertical) direction, bamboo is an anisometric material. This means the the mechanical properties depend on the direction of the force; for instance, compression of the bamboo in the axial direction will result in a different compressive strength then compression in the radial direction. 2) Generally speaking, dry bamboo has higher mechanical properties than wet bamboo. Raw bamboo naturally has a high moisture content, where MC = 100*(wet weight-dry weight)/dry weight. This moisture content can be brought down by using various treatment methods.

3) Generally, smaller bamboo has stronger mechanical properties (such as ultimate compressive strength) for its size. However, larger bamboo can withstand larger forces.

4) Thicker walls have better mechanical properties generally.

5) As the distance to the node decreases, the mechanical properties improve.

6) The height along the bamboo (when measured from the ground) affects its properties. Generally, the part of the bamboo nearer the bottom has stronger properties.

7) Very young bamboo and old bamboo have weaker mechanical properties than bamboo that is around the age of 3-7 years.

8) The species of bamboo also matters; some are not useful as a building material. Because so many properties affect bamboo, it can be difficult to find bamboo property values which are reliable across a large number of cases. Two reliable charts of mechanical properties are given below.

7.7 Wood based products: veneer, plywood, imperg timber, compreg timber, boards

1. Veener: Veener are thin sheets or slices of wood of superior quality, having thickness varying from 0.4 mm to 6 mm or more.These are obtained with the aid of circular rotary saw or rotary peeling machine and are peeled off the log by a sharp knife in a long continuous sheet by rotating the log on its longitudinal axis. The veener is too thin to be used as a separate, but is glued or cemented to other veeners. The veeners are used in the construction of aircraft.

3. Plywood: Ply wood is made by cementing together several layers of wood which may be thin veeners or thicker boards. The resign should be phenol-formaldehyde resin or urea-formaldehyde. Plywood is made of three or more thin layers of wood bonded together with an adhesive. Each layer of wood, or ply, is usually oriented with its grain running at right angles to the adjacent layer in order to reduce the shrinkage and improve the strength of the finished piece. Most plywood is pressed into large, flat sheets used in building construction. Other plywood pieces may be formed into simple or compound curves for use in furniture, boats, and aircraft.

Sizes: Plywood sheets range in thickness from. 06 in (1.6 mm) to 3.0 in (76 mm). The most common thicknesses are in the 0.25 in (6.4 mm) to 0.75 in (19.0 mm) range. Although the core, the crossbands, and the face and back of a sheet of plywood may be made of different thickness veneers, the thickness of each

must balance around the center. For example, the face and back must be of equal thickness. Likewise the top and bottom crossbands must be equal.

The most common size for plywood sheets used in building construction is 4 ft (1.2 m) wide by 8 ft (2.4 m) long. Other common widths are 3 ft (0.9 m) and 5 ft (1.5 m). Lengths vary from 8 ft (2.4 m) to 12 ft (3.6 m) in 1 ft (0.3 m) increments. Special applications like boat building may require larger sheets

Advantage:

1. Better appearance and available in large size.

2. Easily workable and capable of being shaped to numerous designs.

3. Elastic material, least affected by changes in atm.

4. Uniform tensile strength in all directions.

5. Light in weight and greater strength.

6. Highly resistant to cracking, warping

Uses: Construction of aircraft parts, furniture, partitions, ceiling covers, doors, window, packing cases and decorative inside and outside building walls, shops and buses.

3. Board:

a.
Lamin Board: Lamin board is a board having a core of strips, each not exceeding 7 mm in thickness glued together face to face to form a slab which is glued between two or more veeners. The lamin board is light, strong and do not split or crack easily.

Uses: Used in Walls, ceilings, partitions and packing cases.

b.
Block Board: A block board is constructed in the same way as lamin board. In this the core consists of smaller timber block upto 25 mm in width. These blocks are cementededge to edge and on each face piles upto 3 mm thickness are glued.

Uses: Construction of railways carriages, bus bodies, marine and river craft, furniture making, partitions, paneling, prefabricated houses

c. Batten Board: A batten board is a board having a core made up of strips of wood usually 80 mm wide, each laid separately or glued and glued between two or more outer veeners. Uses: These boards are used for door panels, table tops.

4. Impreg timber: The impregnation process is carried out by using autoclave, where chemicals are impregnated into timber using vacum and pressure:

Ø Timber will be taken into autoclave and primary vacum is established. Timber cells will be purged of air and vacum will be stored;

Ø Autoclave is filled with timber preservative;

Ø Pressure is used to compress protective chemicals into timber cells;

Ø Autoclave is emptied and cleaned from timber protective chemicals;

Ø With final vacuuming process, excess preservative dilution will be removed, and is pumped back to reserve tank;

Ø Palivere impregnation autoclave is able to fit materials up to 20m in length, the inside diameter of the autoclave is 2,6m.

Compreg timber:

Compreg is a very special timber composite material with exquisite mechanical properties. The generic name compreg indicates that it is both impregnated and compressed. It is used in applications where long durability, hardness, and dimensional stability is required e.g. gears, rolls and wear strips of industrial conveyors, woodworking machine tables or lining of car floors. Due to special build, compreg is resistant to X-rays, which is being used in medical and military applications. However, by no means is it only a material for industrial applications. Regardless of its hardness, it is comparatively easy to machine, which makes it an excellent choice for manufacturers of exclusive wood working products

8 Miscellaneous Materials

8.1 Types, properties and uses of Asphalt, Bitumen and Tar

8.1.1 Asphalt

Asphalt is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It is formed by partial evaporation or distillation of certain petroleum oils. It is soluble in varying degree in carbon disulphide. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch. Until the 20th century, the term asphaltumwas also used.

Properties:

Ø It is sticky or adhesive and binds strongly as cement.

Ø It is usually solid or semi solid in state.

Ø It is black brownish in colour.

Ø It is water proof.

Ø It is durable and retains its properties for several years.

Ø It is elastic in nature.

Ø It becomes plastic and workable when heated.

Ø It possesses binding properties when soften by heat.

Ø It is not seriously affected by adverse weather.

Ø It is good conductor of heat, sound and electricity.

Ø It is ductile and can be stretched without breaking.

Ø It is soluble in varying degree in carbon disulphide

Types:

1. Natural Asphalt:

a. Lake Asphalt-It is obtained from lakes at Trindad and Bermudez (South America) at depths of 3 to 60m. It is composite mineral containing 40-70 % of pure bitumen.

b. Rock Asphalt: It is natural asphalt impregnated in limestone rocks found in some parts of Switzerland, France and Germany. It contains 4-20 % pure bitumen by volume, the rest consists of calcareous materials.

2. Residual and Petroleum Asphalt: It is also known as artificial asphalt and obtained by the fractional distillation of crude petroleum oils with an asphaltic base.

Uses: Road and Pavement construction, Roofing sheets, paving tiles, Bituminous paint, repairing roofs, Damp-proofing material and water proofing material, flooring, filler for expansion joints in concrete.

8.1.2 Bitumen

Bitumen is defined as solid or semi-solid, black, sticky, ductile substance obtained as a by-product from the distillation of crude petroleum.

Properties:

Ø It is defined as solid or semi-solid, black, sticky Ø It melts or softens on application of heat.

Ø Its specific gravity is 1.09.

Ø It is completely soluble in carbon disulphide.

Ø It possesses great chemical stability but is affected by oil.

Ø It has high insulation resistance.

Uses:

Ø Used as DPC in walls, foundation and lining tanks, swimming pools, urinals.

Ø Used as a filler for expansion joints.

Ø Used as a pavement making material.

Ø Used as heat insulating materials in buildings.

Ø It is also employed in the manufacturing of impermeable paints and bituminous plastics.

Forms of Bitumen:

1. Cutback bitumen: It is obtained by fluxing asphaltic bitumen in the presence of some suitable liquid distillates of coal or petroleum. It is used as bitumen paint.

2. Plastic bitumen: It comprises bitumen thinner and suitable inert filler (40-45%). It is used for stopping leakages and filling cracks in masonary structures.

3. Blown Bitumen: It is obtained by passing air under pressure at high temperatures. It is used as heat insulating material, roofing and damp-proofing felts.

4. Straight run bitumen: It is the bitumen which is being distilled to definite viscosity or penetration without further treatment.

5. Bitumen emulsion: It is the liquid product containing bitumen in a very finely divided state to a great extent in an aqueous medium. A number of technologies allow asphalt/bitumen to be mixed at much lower temperatures. These involve mixing with petroleum solvents to form "cutbacks" with reduced melting point, or mixtures with water to turn the asphalt/bitumen into an emulsion. Asphalt emulsions contain up to 70% asphalt/bitumen and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock, gravel or crushed slag. Slurry seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on

the surface of a road. Cold-mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth and asphalt emulsions are also blended into recycled hot-mix asphalt to create low-cost pavements.

8.1.3 Tar:

It is a black solid mass obtained during the destructive distillation of coal, wood and organic material.

Properties:

Ø Tar contains 75-95 % of bituminous contents.

Ø It contains higher % of carbon.

Ø It hardens much quicker than asphalt.

Ø It is more adhesive than asphalt.

Ø It possesses toxicity to a high degree.

Uses:

Ø It is used for roofing and road making.

Ø It is used to make bituminous paints and water-proofing compounds.

Ø Used as preservative for timber.

Ø Used for the painting for latrine walls.

Types:

1. Coal Tar: It is produced by destructive distillation of coal as a by-product in the manufacture of coal gas. It is used as preservative for timber and tar-macadam roads.

2. Mineral Tar: It is produced by distillation of bituminous shales. It is used in inferior quality roads.

3. Wood Tar: It is produced by distillation of pure and resinous tree. It contains creosote oil and possesses strong preservative property.

8.2 Types, properties and uses of Glass, Plastics and Rubber

PLASTIC:

Plastics are "one of the greatest innovations of the millennium" (on the cover of Newsweek) and have certainly proved their reputation to be true; it has been the most used material in the around the globe. There are a myriad ways that plastic is and will be used in the years to come. The fact that plastic is lightweight, does not rust or rot, helps lower transportation costs and conserves natural resources is the reason for which plastic has gained this much popularity. Plastics are everywhere and have innumerable uses. Plastics are durable, lightweight, and reusable. Also, they are used in packaging many goods. These days researches are trying to make a television (made of plastic) that will roll up in our living room.

General Uses:

Shopping

Just consider the changes we've seen in the grocery store in recent years. Plastic wrap helps keep meat fresh while protecting it from the poking and prodding fingers of your fellow shoppers. Plastic bottles mean you can actually lift an economy-size bottle of juice. And should you accidentally drop that bottle, it's shatter-resistant. In each case, plastics help make your life easier, healthier and safer.

Grocery Cart vs. Dent-Resistant Body Panel

Plastics also help you get maximum value from some of the big-ticket items. Plastics help make portable phones and computers that really are portable. They help make major appliances - such as refrigerators or dishwashers - resist corrosion, last longer and operate more efficiently. Plastic car fenders and body panels resist dings, so we can cruise the grocery store parking lot with confidence.

Packaging

Modern packaging -- such as heat-sealed plastic pouches and wraps -- helps keep food fresh and free of contamination. That means the resources that went into producing the food aren't wasted. It's the same thing once you get the food home -- plastic wraps and resealable containers keep your leftovers protected. In fact, packaging experts have estimated that each pound of plastic packaging can reduce food waste by up to 1.7 pounds.

Lightweighting

Plastics engineers are always working to do even more with less material. Since 1977, the 2-liter plastic soft drink bottle has gone from weighing 68 grams to just 51 grams today, representing a 25 percent reduction per bottle. That saves more than 206 million pounds of packaging.

Doing more with less helps conserve resources in another way. It helps save energy. In fact, plastics can play a significant role in energy conservation. Just look at the decision you're asked to make at the grocery store check-out: "Paper or plastic?"

Not only do plastic bags require less total energy to produce than paper bags, they conserve fuel in shipping. It takes seven trucks to carry the same number of paper bags as fits in one truckload of plastic bags.

Use of plastic in building construction:

1. Plastic Sheets:

a. Polyvinyl Chloride (PVC) sheets: Used in exposure condition like roofing for vegetations.

b. Fabric-backed sheets: used in foot-traffic in dry conditions.

c. Polythene sheets: Sheltering material from rain at construction site and assist curing of concrete. It is also used as temporary material for covering of door and window openings.

d. Corrugated Plastic Sheet: Used for roofing purpose in building and industries.

2. Plastic Tiles: PVC tiles: used for flooring, Fabric-backed PVC tiles are used as paving floors in dry conditions, Thermoplastic Vinyl tiles are used on wooden and concrete sub-floor and Polytyene wall tiles are used as lining wall of high class buildings.

3. Plastic Laminates: Used for decorative purposes in wall paneling, table and counter parts.

4. Plastic Panels: Used for partition works.

5. Plastic Pipes: PVC pipes are used for distribution of water, mine drainage, gas distribution and

Polythene plastic pipes are used in water supplies and food industries

8.1 Gypsum product and composite material;

Ø The gypsum (CaSO4.2H2O) seldom occurs in nature in pure state; it contains impurities such as alumina, calcium carbonate, magnesium carbonate and silica.

Ø It is white crystalline substance sparingly soluble in water.

Ø It is soluble in HCl and insoluble in Sulfuric acid.

Ø It sets and hardens quickly

Properties of gypsum products:

Ø Good Sound absorbers

Ø Possess small bulk density

Ø Incombustible

Ø Poor state in wet state

Ø Develop high creep under load.

Uses:

Ø It is used as filler in paint, paper and rubber industries.

Ø It is used in manufacturing of cement to increase setting time.

Ø Used to prepare the plaster of paris (calcium sulphate hemihydrate) and gypsum boards.

Composite Materials: A composite material is a combination of two or more materials having compositional variation and depicting properties distinctively different from those of the individual materials of the composite. The composite material is generally better than any of the individual components as regards their strength, heat resistance and stiffness. Composite includes the following; Ø Multiphase metal alloys

Ø Ceramics- Ceramic materials are inorganic, non-metallic materials made from compounds of a metal and a non metal

Ø Polymers- consisting of many small molecules (called monomers) that can be linked together to form long chains

Natural composites: Natural composites exist in both animals and plants. Wood is a composite

– it is made from long cellulose fibres (a polymer) held together by a much weaker substance called lignin. Cellulose is also found in cotton, but without the lignin to bind it together it is much weaker. The two weak substances – lignin and cellulose – together form a much stronger one. Early composites: People have been making composites for many thousands of years. One early example is mud bricks. Mud can be dried out into a brick shape to give a building material. It is strong if we try to squash it (it has good compressive strength) but it breaks quite easily if we try to bend it (it has poor tensile strength). Straw (plant-product) seems very strong if we try to stretch it, but we can crumple it up easily. By mixing mud and straw together it is possible to make bricks that are resistant to both squeezing and tearing and make excellent building blocks.

Another ancient composite is concrete. Concrete is a mix of aggregate (small stones or gravel), cement and sand. It has good compressive strength. In more recent times it has been found that adding metal rods or wires to the concrete can increase its tensile (bending) strength. Concrete containing such rods or wires is called reinforced concrete

References:

1. Joshi, Buddhi Raj (2010): Civil Engineering Material Lecture Notes, SoE, Pokhara University

2. Rajput, R.K. (2004). Engineering material, New Delhi: S.Chand & Company Ltd.

3. Sing, P. (2008). Civil Engineering material. Katson Books.

4. Khurmi R.S & Sedha. Material science and Processes. New Delhi: S. Chand and Company Ltd.

5. Peter A. Thronton & Vito J. Colangelo (1985). Fundamentals of Engineering Materials. Prentice hall

About Me

Monday, May 6, 2024

civil Engineering Materials note

1 Material Science:

1.2 Types of Civil Engineering Materials (metals, timber, ceramics, polymers, composites)

Other types of Construction Materials are:

1.3 Properties of Civil Engineering Materials

1.4 Material-Environment (Temperature, humidity, rain and fire) Interaction

3 Stone and Aggregate

3.1 Physical Classification of Rock/Stone:

3.2 Quarrying, Dressing and Seasoning of stone:

3.3 Artificial Stone

3.4 Classification of Aggregate:

3.5 Gradation of Aggregate:

3.6 Fineness Modulus of Aggregate:

3.7 Bulking of sand (Fine Aggregate)

3.8 Testing of Coarse Aggregate

3.8.2 Shape Test of Aggregate:

3.8.3 Flakiness index and Elongation Index of Coarse Aggregates

3.8.4 Aggregate Abrasion Value

3.8.5 Aggregate Impact Value

3.8.6 Aggregate Crushing Value

3.8.7 Sodium Sulphate Soundness Test:

4 Cement

4.2 Lime

4.3 Indian standard classification of lime

4.4 Cement, its composition (Bogue compounds) and properties, Cement manufacturing process

Depending upon mixing and grinding Manufacturing are:

4.5 Hydration, Heat of Hydration and gain of strength of cement:

4.6 Types of Cement (OPC, PPC, RHC, white cement) and their uses:

4.7 Testing of cement (fineness, soundness, consistency, setting time, compressive strength and tensile strength)

1. Fineness test of cement by sieve test:

Apparatus:

Reporting of Results:

2. SOUNDNESS:

Method:

3. CONSISTENCY TEST OF CEMENT

SETTING TIME TEST

A) INITIAL SETTING TIME:

B) FINAL SETTING TIME:

F

Fig: Universal Testing Machine (UTM)

4.8 Mortar: function and types (mud, lime, cement and gauged)

Function of Mortar:

Mud Mortar:

Uses:

Gauzed Mortar:

Uses:

5 Mechanical Behavior

5.1 Types of stress/strains (True and Engineering) and their relationship

5.2 Stress-Strain Curve of Ductile and Brittle material

E= σ/ ε

5.3 Fracture of metal: ductile and brttle

σmax= 2σ √(c/r)

UE = - (π c2 σ2) / E

US = 2×(2c×1) × γ = 4cγ

d (U)/dc = d/dc {(-2π c2 σ2) / E + 4cγ} = 0

σ = √ (2γE / πc)

Cc = 2γE / π σ2 σ = √ (2γE / π) × 1/√c

σ = k × 1/√c

σ α 1/√c

5.4 Hardness: Types (Scratch, indentation and rebound) and its tests (Brinell and rockwell)

5.5 Impact Strength and its Test (Charpy and Izod)

6 Metals and Alloys

6.1 Iron: types, manufacturing process, properties and uses Ferrous and Non-ferrous Metals

Manufacture of Wrought Iron

(C) Cast Iron:

Uses:

Uses:

6.2 Steel: composition and types (carbon and alloy steel)

The Bessember Process

Stages

6.3 Types of carbon steel and their uses

(b) Medium Carbon Steel:

6.4 Properties, advantages and uses of stainless steel, tool steel, brass, aluminium and duraluminum

(b) Stainless Steel

(c) Spring Steel:

(d) Heat Resistive Steel (HRS):

BRASS:

4. Aluminium Brass: Cu, Zn, Al upto 5%

UE = - (π c² σ²) / E

Cc = 2γE / π σ²

σ = √ (2γE / π) × 1/√c