Portland cement concrete is the most widely used construction material in the world. It is estimated that concrete is second only to water as the world’s most utilised substance. The estimated world consumption of concrete in 2006 was approximately 11 billion tons. The reasons for this wide use are varied, but among the more important are availability and affordability of its constituents; its versatility and adaptability, as evidenced by the many types of construction in which it is used; the ease with which structural elements can be formed into an almost limitless variety of shapes and sizes; and the minimal maintenance requirements during service. Concrete is unique among major construction materials in that it is generally designed specifically for a particular project using locally available materials.