Lightweight concrete substitutes a lighter material for the common stone aggregate found in most concrete. Builders use various lightweight aggregates in conjunction with standard sand and cement to form the concrete. Builders currently use lightweight concrete in some low-stress construction applications and in decorative pieces. Various products provide the lightweight component of the concrete.
Materials such as perlite, fly ash, expanded clay or slate or pumice replace the common stone aggregate, reducing the weight of the concrete. Pumice or scoria is a light volcanic stone containing voids or air pockets. These materials replace the heavier shale, granite or other stones used for aggregate material. Aggregate pieces are commonly 3/4- to 1 1/2-inch pieces.
The lighter the concrete, the better its thermal insulating quality. The material also possesses greater sound insulation qualities than standard concrete. For these reasons, builders often use lightweight cement for pre-cast walls and other non-load bearing building components.
Lightweight cement weighs less than normal cement, but it still isn’t light. The term refers to any cement weighing between 85 and 115 lb. per cubic foot. Normal concrete weighs in at about 150 lb. per cubic foot. The lighter the aggregate, the lighter the resulting concrete. Builders can specify the light aggregate for the project. The decision to use lightweight concrete, and which light aggregate to use, depends on the weight of the cement versus its strength.
Structurally lightweight concrete is used for pre-cast walls and occasionally as an insulating agent in poured walls. Other uses include cast garden statuary and decorative items. The finer aggregates, such as perlite, are common for the decorative items. Lightweight cement possesses less compression strength than standard cement, which is still commonly used for structural components of buildings.