CONCRETE
Concrete is a composite man-made material and is the most widely used building material in the construction industry.
Concrete is a mixture of binding material such as lime or cement, well-graded coarse and fine aggregate, water, and sometimes admixtures.
Most of the ancient structures and historical buildings had been constructed with lime concrete but with the invention of cement, the use of lime concrete is limited to making bases of concrete foundations and roof terracing.
Also, the production of good concrete is found difficult.
Now a question arises what is “Good concrete”.
- The basic requirement of Good concrete is that it should be satisfactory in its hardened state, and also in its fresh state while being transported from the mixture and placed in formwork.
- In a fresh state, the consistency of the mix should be such that it can be compacted by the desired means without excessive effort, and also the mix should be cohesive enough for the methods of transporting and placing used so as not to cause segregation.
- In a hardened state satisfactory compressive strength and adequate durability are required.
CLASSIFICATION OF CONCRETE
1. Based on Cementing Material
(a) Lime concrete (b) Gypsum concrete (c) Cement concrete
2. Based on Perspective Specification
- Cement concrete is specified by proportions (by weight) of different ingredients, e.g., 1 (cement) : 1.5 (fine aggregate) : 3 (coarse aggregate).
- It is presumed that by adhering to such perspective specifications satisfactory performance may be achieved. This type of concrete mix is also known as the nominal mix.
- Conventional nominal mix proportions have limited significance since the quantity of fine aggregate is irrespective of the cement content- water ratio, and the maximum size of aggregate to be used.