Lightweight concrete weights 20-40% less than normal concrete. Its primary use is to reduce the weight or dead load of a structure. This allows for flexibility in the structural design of load bearing elements in building. Lightweight concrete is most commonly used on slabs on suspended metal decks, bridge decks and parking structures.
Concrete mixes use lower density coarse aggregate such as expanded shale, clay or slate. These aggregates are specially treated to develop a porous structure by being fired in a rotary kiln. Lightweight benefits by providing a higher fire-rating while improving energy conservation.