As discussed above, the materials used for R.C.C. are cement, fine aggregate, coarse aggregate, water and steel reinforcement in shape of bars.
Cement is used as building material. Generally, port-land cement conforming to I.S.I. specification is used.
- Fine Aggregate
Aggregates are obtained from sedimentary igneous and metamorphic rocks. The aggregate which passes through IS Sieve No.480 is called fine aggregate. The particle size of this 8%. Fine aggregate is generally known as sand. It is obtained from the river beds, lake beds, pits etc. It should be free from silt, clay, salts and other organic matter.
- Coarse Aggregate
The aggregates which is retained over IS sieve No. 480 is called coarse aggregate. The size of this aggregate depends upon the type and nature of work. The maximum size used in the construction of building work should be between 20 mm to 25 mm. In the case of heavy mass concrete work for dams, weirs, syphons regulators etc., The size of aggregate may be more than 25 mm. It should be soft, porous, or flaky. It should not absorb more than 5% of water by weight when immersed for 24 hours.
The water used for making concrete should be free from dirt, organic impurities, sulphur contamination and chlorides which cause eflorescence. The clear water used for drinking purposes should be used. Sea water contains chlorides which may corrode reinforcement hence it should be avoided.
Steel is used as reinforcement which should be free from loose mill scales, dust, loose rust and coats of paints, oil or other coatings which may destroy or reduce bond. Round bars of mild steel between 5 mm to 50 mm diameters having high tensile strength should be used. Steel is used as reinforcement because its co-efficient of expansion is nearly same as that of concrete and can develop good bond with concrete and can be freely available.
Advantages of Reinforced Cement Concrete (R.C.C.)
Reinforced cement concrete (R.C.C.) has following advantages:
- It is easy to make.
- It can be molded to any desired shape.
- The materials for its preparation are easily available.
- It is durable.
- It is fire resisting.
- It can be made water-tight by using proper proportions of mix.
- It is more rigid.
- It has low maintenance cost.
- It can be used under water.