Materials of Constructions in Civil

1. Traditional Materials
The building materials such as stones, bricks and timber are called traditional building materials since these materials are used from the early ages of civilization. Cement, cement-mortar and cement-concrete are also grouped under traditional materials although they are of recent origin compared to stones and bricks. The properties and uses of some of the most commonly used traditional building materials have been discussed here.

a. Stones
Stones are obtained from rocks. A rock represents a definite portion of earth’s surface. Process of taking out stones from natural rock beds is known as quarrying. The term quarry is used to indicate the exposed surface of natural rocks. Stones, thus obtained, are used for various engineering purposes.

Properties: A good building stone should have the following qualities.

1. Crushing Strength: For a good structure stone, the crushing strength should be greater than 100 N/mm2.
2. Hardness: For a good building stone, the coefficient of hardness should be more than 17.
3. Fracture: For a good building stone, its fracture should be sharp, even and clear.
4. Percentage wear: The percentage wear should be equal to or less than 3%.
5. Resistance to fire: Minerals composing stone should be such that shape of stone is preserved when a fire occurs.
6. Water absorption: For a good stone, percentage absorption by weight after 24 hours should not exceed 0.6.
7. Specific gravity: A good building stone should have a specific gravity more than 2.7. Compact and less porous building stones will have higher specific gravity.
8. Durability: A good build stone possesses higher resistance against the action of weathering agents. Durability is affected by chemical composition, resistance to atmospheric agents, physical structure etc.
9. Appearance: Stones which are used for face work should be decent in appearance and they should be capable of preserving their colour uniformly for a long time.
10. Seasoning: Stones should be well seasoned before putting into use i.e., they should be free of moisture content (quarry sap). Stones should be dried or seasoned before they are used in structural work.

Uses of Stones:
1. Stones are used as a construction material for foundations, walls, columns and lintels.
2. Stones are used for face-work of buildings to give good appearance.
3. Thin stone slabs are used as roofing and flooring material.
4. Crushed stones are used for production of cement concrete.
5. Crushed stones are also used as ballast for railway track.
6. Aggregate of stone is used as a road metal.

b. Bricks: Bricks are obtained by moulding clay in the rectangular blocks of uniform size and then by drying and burning these blocks. Bricks are very popular as they are easily available, economical, strong, durable and reliable. They are also reasonably heat and sound proof. Thus, at places where stones are not easily available, but if there is plenty of clay, bricks replace stones.

Properties of bricks: Good bricks which are used as building material should possess the following qualities.
1. Bricks should be uniform in shape and should be of standard size.
2. Bricks should be table moulded, well burnt in kilns, copper coloured, free from cracks and with sharp and square edges.
3. Bricks should give clear ringing sound when struck with each other.
4. Bricks when broken should show homogeneous and compact structure.
5. A brick should not absorb more than 15% of its weight of water when kept immersed for 24 hours.
6. The crushing strength should not be less than 5.5 N/mm2.
7. Bricks should be sufficiently hard such that no impression is left when scratched with finger nails and they should be free of soluble salts.
8. A brick should not break when dropped from a height of about one metre.

Uses of Bricks:
1. Bricks are extensively used as a leading material of construction.
2. A fire brick (Refractory brick) is used for lining the interiors of ovens, chimneys and furnaces.
3. Broken bricks are used as a ballast material for railway tracks, and also as a road metal.
4. Bricks are extensively used for construction of load-bearing walls and partition-walls.
5. Bricks are also used for face-work when artistic effect is required.

c. Timber:
The word timber is derived from ‘Timbrian’ which means to build. Timber thus denotes wood which is suitable for building construction, carpenting or other engineering purposes. When it forms part of a living tree it is called ‘Standing timber’, when felled it is known as ‘Rough timber’ and when cut in to different forms such as planks, beams etc., it is known as ‘Converted timber’.

Properties of timber
1. Strength: A good timber should have high strength in bending, shear and direct effects so that it can be used as a structural member such as beam or column.
2. Appearance: A good timber possesses fine and even texture, close grains and shining dark appearance.
3. Durability: A good timber should be durable and capable of resisting the actions of fungi, insects, chemicals and physical agencies.
4. Hardness and Toughness: A good timber will be hard and capable of resisting shock loads.
5. Seasoning: Seasoning is the process of removal of water from the freshly cut timber when is present in the form of sap and moisture. A good timber is to be well seasoned before using it for any engineering purposes.
6. Resistance to fire and thermal expansion: A good timber should have high resistance to fire. Timber has very low coefficient of thermal expansion parallel to grains and is a bad conductor of heat.
7. Workability: A good timber should be easily workable and should not clog the saw and can be planed easily.
8. Defects: A good timber should be free from serious defects like knots, flaws, shakes etc.

Uses of Timber:
1. For making doors, windows and ventilators.
2. Used as flooring and roofing material.
3. Used for making furniture.
4. Used in making agricultural implements.
5. Used in the manufacture of sport goods, musical instruments etc.
6. Used in making railway coaches, wagons, buses, boats etc.
7. Used in making sleepers for railways, fencing poles, electric poles, footways, bridge floors, temporary bridges etc.
8. Soft wood is used for manufacture of paper, card-boards, walls paper etc.

d. Mortar:
The term mortar is used to indicate a paste prepared by adding required quantity of water to a mixture of binding material and sand. The most common binding material used in the preparation of mortar is cement. Such a mortar is called cement-mortar.

Properties of mortar
1. Strength: The compressive strength of cement-mortar varies from 1 N/mm2 to 10 N/mm2 depending upon mix proportion of cement and sand and water added to it.
2. Durability: Good cement-mortar can effectively withstand the adverse effects of weathering agents such as rain, wind and sun light.
3. Impermeability: Mortars should be impervious and act as a water-tight layer.
4. Shrinkage: Mortar exhibits tendency to shrink during setting process and likely to develop hair-line cracks. Mortars with rich cement mix are prone to high shrinkage.
5. Binding strength: When water is added to the dry mix of cement and sand, the hydration process of cement starts and cement binds the sand particles and the surrounding surfaces of masonry and concrete. A good mortar possesses high binding strength.

Uses of mortar
1. Mortar is used as a binding material for brick and stone masonry constructions.
2. Mortar is used to carry out pointing and plastering work on exposed surfaces of masonry.
3. Mortar is used to provide fine finish to concrete works.
4. Mortar is used for decorative finish to masonry walls and roof slabs.
5. Mortar is used as a filler material in ferro-cement works.

e. Cement concrete
Cement concrete is an artificial product obtained by hardening of the mixture of cement, sand, gravel and water in pre-determined proportions. The hardening of cement-concrete is due to chemical reaction between cement and water and the process is also called ‘setting’.

Properties of cement-concrete
Properties of concrete are different when it is in plastic stage (green concrete) and hardened stage.

Properties of Green Concrete:
1. Workability: The workability of a freshly prepared concrete is the ease with which it can be mixed, placed, compacted and finished without affecting homogeneity.
2. Segregation: A good concrete is a homogeneous mixture of cement, sand, coarse aggregates and water. Segregation during mixing, placing and compacting affects strength, durability and water tightness.
3. Bleeding: Bleeding is the separation of water cement slurry from coarse and fine aggregates either due to excessive quantity of water in fresh concrete or due to excessive vibration during compaction process. Bleeding of concrete causes formation of pores and reduces compressive strength.
4. Harshness: Harshness of concrete is due to use of poorly graded aggregates in concrete mix. A harsh concrete is porous and difficult to get smooth surface finish.

Properties of hardened Concrete
1. Strength: Hardened concrete should have high compressive strength. Compressive strength is the most important parameter considered in the design of concrete structures.
2. Durability: Concrete should be capable of withstanding the adverse effects of weathering agents such as wind and water. In addition, it should resist temperature variation, moisture variation, freezing and thawing.
3. Impermeability: Hardened concrete should be impermeable or water-tight. This property of concrete is considered in the construction of water tanks and bins.
4. Resistance to wear and tear: Hardened concrete should be capable of with standing abrasive action during its usage. When concrete is used as a flooring material, or for construction of cement concrete roads, it should withstand abrasive action.

Uses of Cement Concrete
1. It is used for making Reinforced Cement Concrete (R.C.C.) and Prestressed Cement Concrete (P.S.C.).
2. It is used for mass concrete works such as dams and bridges.
3. It is used for making electric poles, railway sleepers and high rise towers.
4. It is used for the construction of silos and bunkers.
5. It is used for the construction of water tanks and under water construction.
6. It is used for the construction of road pavements and air port pavements.
7. It is used for construction of arches and ornamental structures.
8. It is one of the best universally accepted construction material and used in various civil Engineering works.

Reinforced Cement Concrete (R.C.C.)

Plain concrete can withstand very high compressive loads. But it is very weak in resisting tensile loads. Steel, on the other hand can resist very high tensile force. Hence, steel is embedded in concrete whenever tensile stresses are expected in concrete. Such a concrete is called ‘Reinforced Cement Concrete’.

Properties of R.C.C.
1. R.C.C. is highly economical when compared to other engineering materials.
2. R.C.C. is durable and can effectively resist moisture variation and temperature variation.
3. R.C.C. is a fire resistant construction material.
4. Water-tight structures such as water tanks can be constructed of R.C.C.
5. R.C.C. can be moulded to any shape and size before setting and hardening of concrete.

1. R.C.C. is used for construction of structural elements such as beams, columns and slabs.
2. R.C.C. is used for the construction of water tanks, storage bins, bunkers, tall chimneys, towers etc.,
3. R.C.C. is used in making raft foundations and pile foundations.
4. R.C.C. is used in the construction of bridges, marine structures, aqueducts, high rise buildings and many other civil engineering works.

• Stones, bricks, timber and concrete are grouped under traditional building materials
• Stones are characterised by high crushing strength, high hardness and very high durability. Stones are used as a construction materials for foundations, walls, columns, roofing & flooring material and as aggregate in production of concrete
• Bricks are produced by moulding clay in the rectangular blocks. They are economical and reliable building material. Bricks are extensively used as a leading material of construction and at places where stones are not easily available, bricks replace stones.
• Timber denotes wood which is suitable for building construction. A good timber is characterised by high strength in bending and shear and capable of resisting shock loads. It is extensively used for making door and window frames, trusses and furniture. It is also used as a material for temporary structures such as scaffolding and temporary bridges.
• Mortar is prepared by adding water to mixture of cement and sand. A good mortar possesses high binding strength. It is used as a binding material for masonry constructions.
• Concrete is produced by mixing cement, sand gravel and water in definite proportions. It is characterised by high compressive strength and resistance to wear and tear. It is used for mass concrete works in dams and bridges, for making Reinforced Cement Concrete and Prestressed Cement Concrete and other Civil engineering works.
• Steel is embedded in concrete whenever tensile stresses are expected in concrete. Such a concrete is called reinforced cement concrete. R.C.C. is used for construction of structural elements such as footings, columns, beams and slabs.