lightweight cement mix is a type of concrete that has lower density than normal-density concrete. It has a higher porosity than traditional concrete, making it an excellent option for projects that require insulation from heat damage.

Several basic forms of lightweight concrete are commonly available. These include no-fines concrete (NC), aerated or foamed concrete and lightweight aggregate concretes.

NC consists of aggregates that are fully or partially omitted to create air-filled voids using a process pioneered by Wimpey in the UK in 1924 (no-fines concrete). These voids are formed in the form of bubbles of gas trapped within a concrete paste or mortar matrix and are primarily responsible for the structural properties of NC.

Aerated or foamed concrete involves including bubbles of gas within a cement paste or mortar matrix to form a cellular structure with approximately 30-50 per cent voids. This enables the concrete to function as an internal curing material.

Aggregates for lightweight concrete can be sourced from many different sources, including sand, clay and silica sand, shale, slate and volcanic pumice. The most common source of aggregate is pumice, a glass that forms when frothy lava cools quickly into rock. Other types of natural materials, such as cinders and perlite, are also sometimes used to produce lightweight concrete.

Several combinations of aggregates are available and may influence the concrete’s final properties, particularly its strength, and the use of lightweight concrete is a rapidly developing field of research, practice and technology. The influencing factors of the final product are varied and often difficult to understand on a job-by-job basis. This can make mix design and production more complicated than with traditional concrete, especially where the resulting compressive strength is critical.