In this article :
Learn Plain cement concrete, Reinforced cement concrete, Composite action of steel and concrete, Uses of Reinforced concrete, Advantages of R.C.C. ,Disdvantages of R.C.C.
Plain Cement Concrete
Plain Cement Concrete is a hardened mass obtained from a mixture of cement, sand, gravel and water in definite proportions. These ingredients are mixed together to form a plastic mass which is poured into desired shape moulds called as forms. This plastic mass hardens on setting and we get plain cement concrete. The hardening of this mixture is caused by a chemical reaction between cement and water.
Plain cement concrete has good compressive strength but very little tensile strength, thus limiting its use in construction. Plain concrete is used where good compressive strength and weight are the main requirements and tensile stress are very low.
Reinforced Cement Concrete
Plain cement concrete has very low tensile strength. To improve the tensile strength of concrete, some sort of reinforcement is needed which can take up the tensile stresses developed in the structure. The most common type of reinforcement is in the form of steel bars which are quite strong in tension.
The reinforcing steel is placed in the forms and fresh concrete is poured around it. This solidified composite mass is called as Reinforced cement concrete and is abbreviated as R.C.C. Thus, Reinforced cement concrete is a composite material which is made up of concrete and steel reinforcement. The steel reinforcement, generally in the form of steel bars, are placed in the tensile zone of the structure and take up the tensile stresses. R.C.C. is a versatile construction material which is strong in compression as well as tension. The use of reinforcement in concrete not only increase its strength but also helps in preventing the temperature and shrinkage stresses.
Composite action of steel and concrete
The composite action of steel and concrete in a reinforced concrete section is dependent on the following important factors :
(i) The bond between steel and concrete.
(ii) Prevention of corrosion of steel bars embedded in the concrete.
(iii) Practically equal thermal expansion of both concrete and steel.
Uses of Reinforced Concrete
Reinforced cement concrete has innumerable uses in construction some of which are listed below :
- Water Tanks
- Road and Rail Bridges
- Chimneys and Towers
- Retaining Walls
- Bunkers and Silos
Advantages of R.C.C.
R.C.C. has very good strength in tension as well as compression.
R.C.C. structures are durable if designed and laid properly. They can last up to 100 years.
R.C.C. sections can be given any shape easily by properly designing the formwork. Thus, it is more suitable for architectural requirements.
The steel reinforcement imparts ductility to the R.C.C. structures.
R.C.C. is cheaper as compared to steel and prestressed concrete. There is an overall economy by using R.C.C. because its maintenance cost is low.
The raw materials which are required for R.C.C. i.e., cement, sand aggregate, water and steel are easily available and can be transported easily. Nowadays Ready Mix Concrete (RMC) is used for faster and better construction. (RMC is the concrete which is manufactured in the factory and transported to the site in green or plastic state).
Fire Resistance :
R.C.C. structures are more fire resistant than other commonly used construction materials like steel and wood.
R.C.C. is almost impermeable to moisture.
Seismic Resistance :
Properly designed R.C.C. structures are extremely resistant to earthquakes.
Disadvantages of R.C.C. :
Despite the above mentioned advantages, R.C.C. has following disadvantages :
- R.C.C. structures are heavier than structures of other materials like steel, wood and glass etc.
- R.C.C. needs lot of form-work, centering and shuttering to be fixed, thus require lot of site space and skilled labour.
- Concrete takes time to attain its full strength. Thus, R.C.C. structures can’t be used immediately after construction unlike steel structures.