The formula for concrete calculations is (length x width x depth) divided by 27. The result of this formula provides the number of cubic yards of concrete needed. The measurements must be in feet in order for the equation to work.
Concrete is comprised of several components including water, Portland cement and aggregate, which is granular material such as sand and rocks. Portland cement commonly comes in a powdered form and is the binding agent in the mixture. Proper hardening of a mixture requires a humid environment to achieve optimal strength. In environments where it is difficult to ensure constant humidity, such as the outdoors, water is sprayed on the concrete, which is covered with a plastic sheet. The aggregate materials provide reinforcement and determine the density of the finished product.
There are a variety of concrete densities. Concrete for standard use is premixed with inexpensive lightweight aggregate such as gravel. High-density concrete require heavyweight aggregates such as barites, magnetite, iron or lead. The use of high-density concrete occurs in the construction of nuclear facilities and places where it is necessary to have high structural integrity while taking up little space. It is more costly than standard concrete, but provides superior shielding against radiation while being more cost effective than lead or steel alternatives.