Chemical Composition of Foaming Agent in Concrete

The chemical composition of foaming agent is important in determining the performance of the concrete. The chemistry of the foaming agent can affect the mechanical properties and thermal conductivity of the concrete.

The water to cement ratio (w/c) has a significant effect on the microstructure of foam concrete. When the w/c ratio is below the optimal limit, thinner-walled and irregular foams are formed, causing the compressive strength of the concrete to decrease. In contrast, when the w/c ratio is above the optimal limit, bubbles are easier to coalesce and larger pores are formed.

Superplasticizers are often used in foam concrete to reduce the water to cement ratio, and maintain satisfactory fluidity during production of the foam. This decreases the water demand, improves workability and increases the compressive strength of the foam concrete.

Fly ash [41] can also be used in foam concrete to improve its workability and thermal conductivity. The interaction between the fly ash and the foaming agent can improve its compressive strength and pore structure, as demonstrated in a study. Moreover, the inclusion of coarse fly ash in foam concrete can result in a smaller pore size and high compressive strength.

Fibers can also be added to foam concrete to increase its water absorption rate. Fibers such as sugar cane pulp fibers have a higher water absorption capacity than sand, so they can be added to foam concrete in order to increase its workability and strength.

The stability of the cellular lightweight concrete depends on the type of aggregate used. Using recycled concrete aggregate instead of fine sand can significantly improve the stability of the cellular lightweight concrete.