Anyone who works with concrete knows that it is heavy—about 150 pounds per cubic foot (pcf) for normal-weight mixes. In many applications, the weight is either advantageous or something we can accommodate easily. But in some applications lighter weight (actually lower density) concrete is a big advantage—either simply because of the reduced weight or for higher fire resistance, noise resistance, or thermal insulating value.
An advantage of lightweight aggregate that has been getting more attention recently is its ability to carry water into the concrete to achieve what is called “internal curing.” Using saturated fine lightweight aggregate, water can be released slowly into the concrete during hydration. This is especially advantageous for high-performance mixes, resulting in higher strength and lower permeability.
When even lower unit weight concrete is needed, or higher insulation value, cellular concrete is the solution. Cellular concrete is created by introducing foam into the concrete mix to result in a matrix of air bubbles. Cellular concrete can be produced at unit weights from 110 pcf to as low as 15 pcf. The newest innovation in cellular is pervious cellular concrete that allows the mix to retain water and to drain.