Constituents - Requirements

Constituents - Requirements

The main constituents of concrete are:

·     Cement / Lime: Before introduction of ordinary Portland cement, lime was used as cementing material. At present most of the cement concrete works in the building construction is done with ordinary Portland cement. But other special varieties of cement such as rapid hardening cement, high alumina cement are used under certain circumstances. The cement should comply with all standard specifications.

·     Fine Aggregates: The material, which is passed through 4.7625mm B.S. test sieve, is termed as fine aggregates. Usually natural river sand is used as fine aggregates. But places where natural sand is not available economically, finely crushed stone may be used as fine aggregates.

·     Coarse Aggregates: The material retained on 4.7625mm size B.S. test sieve is termed as coarse aggregates. Broken stone is generally used as coarse aggregates. For thin slabs, and walls, the maximum size of coarse aggregates should be limited to one third the thickness of the concrete section.

·     Water : Water to be used in the concrete work should have the following properties.

1.                        It should be free from oils

2.                        It should be free from acids or alkalies

3.                        It should be free from Iron, Vegetables matter or other substance, which is likely to have adverse effect on concrete.

4.                        It should be fit for drinking purpose