Whether poured in-situ or precast, foamed concrete can be used to reduce the weight of a structure without compromising its performance. The process is simple and involves mixing a normal batch of concrete with a quantity of air entrapped in the aggregates, using a foaming agent to promote bubble formation. The bubbles then expand into the concrete mix and form a strong lightweight material. Despite the simple process, a number of factors can influence the quality of the finished product such as its strength, density, volume and placement requirements.

Foaming agents are chemicals that reduce surface tension, thus allowing air to enter the liquid mixture and rise to the top of the mix. There are two types of foaming agents, protein based and synthetic-enzyme based. The former requires a large amount of energy to generate foam while the latter can be generated at much lower power consumption. The latter is also capable of generating a much more stable foam and thus, is preferred.

The addition of foaming agent has a tremendous effect on the properties of the resulting concrete, especially its density, flexural and compressive strength. The density and thermal conductivity show a rapid decrease tendency with increasing foam agent addition, while the flexural and compressive strength exhibit a more gradual increase in strength with the same trend.

This is partly due to the fact that foam concrete mixes with smaller sized aggregates tend to have more and wider air voids, while the larger ones are able to be embedded within the bubble network. The use of a high proportion of coarse aggregates, however, can result in a pore structure that is not uniform and can lead to the failure of the bubbles as they expand in the concrete. Narrower pore sizes, on the other hand, have been shown to improve the strength of foam concrete.