The performance of concrete is often a function of the weight (density) of the concrete. The normal weight of concrete is around 150 pounds per cubic foot. However, there is often a need to proportion concrete at a lighter unit weight. When a lighter weight concrete is needed, the weight of the aggregate is the critical proportioning factor.

The most common reasons lightweight concrete is specified is to reduce weight and/or to improve fire resistance. Lightweight concretes have unit weights which vary from 110 to 125 pounds per cubic foot. To achieve these unit weights, Rock Hill utilizes different varieties of high quality lightweight aggregates depending on the application.