ABSTRACT
Concrete is an extremely versatile construction material. Compared with other construction materials it is relatively cheap to produce using natural constituents available in quantity in most parts of the world. Provided that suitable control is maintained over selection of the constituent materials, the way in which they are hatched and mixed, and as long as handling, placing, compaction and curing are properly carried out, the concrete will be capable of sustaining considerable loading in demanding situations. Concrete in its fresh state is a plastic material, the flow characteristics of which can be simply controlled. Initially the gain in strength is rapid, measured in hours, but concrete continues to harden throughout a number of years. For convenience, concrete strength is measured using 28 days at a constant temperature (20°C in Britain) as a reference point.
