PROPERTIES AND PROPORTIONS OF THE CONCRETE.

The properties of the concrete depend to a very large extent on the proportions of the mix , on the thorough ness with which the various constituents are intermixed , and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the forms untill it is fully hardened .The process of controlling these conditions is known as curing. Crushed rock or gravel in the form of a mixture of several fractions can be used as course aggregate.The fine aggregate ie sand is used as for as possible in two fractions .For preparing the concrete mix the fractions of the aggregates are measured separately. The unit weight of the stone concrete ie concrete with natural stone aggregates varies from 23000 N / cubic metres to 24000N/ cubic metres.