lightweight concrete strength refers to the strength of a concrete made with lightweight aggregates. The density of this type of concrete is generally in the range of 90 to 115 lb/ft3 (140 to 1840 kg/m3), compared to normalweight concrete that has a density of 140 to 150 lb/ft3.

There are three basic types of lightweight concrete: no-fines, aerated or foamed, and lightweight aggregate concrete. The no-fines type is produced by omitting a fraction of the fine aggregate to produce air-filled voids (no-fines concrete). Aerated or foamed concretes, which include a small amount of bubbles of gas, are constructed by replacing wholly or partially natural aggregates with lightweight aggregates containing a large proportion of voids.

Moderate-strength lightweight concrete is produced by firing expanded shale, clay or slate materials in a rotary kiln to form a porous structure. Other products such as ash and air-cooled blast furnace slag may also be used.

Weaker-strength lightweight concrete is produced from spongy lava or scoria aggregate. Both spongy lava and scoria have a porous structure with isolated void pores. These types of concrete are typically used for low-strength applications.

Despite their low thermal conductivity, these types of concrete are often used to insulate buildings and walls and insulate steel structures against corrosion. They are also commonly used to construct interstate and traffic lanes.

Unlike structural lightweight concrete, which should be oven-dry to provide its required strength, insulating concrete does not require an equilibrium density or a maximum water-to-cementitious material ratio. However, if the concrete is to be exposed to moisture, it must have an equilibrium density of at least 1.0 percent of its total water content.