Foaming Agent in Concrete

A foaming agent in concrete acts as a solvent to emulsify the water and cement, thus creating a light, strong, flexible, and air-filled mass that is easy to pour. It is also used as a structural filler.

The mix design for foam concrete includes a very low water cement ratio (w/c) compared to standard concreting mixes. The mix may contain pulverised fuel ash or ground granulated blast furnace slag instead of conventional cement. It may also have a higher level of natural fine aggregates to improve the workability and lower the cost of the mix. The fine aggregates are generally mixed in a slurry before being added to the foam.

In the process of mixing a slurry, a mechanical mixer with a rotor is usually employed to ensure thorough and uniform distribution of the mixture throughout the mix. The slurry is then passed through a nozzle to form the foam. This nozzle is positioned within the mixer drum. A selected substance is then mixed into the slurry at a rate of 13-17 wt. % of the foaming agent and is incorporated into the foam by a shear force generated by rotation of the rotor.

Specimens with different densities of foamed concrete were produced and tested according to PN-EN 12390-7:2011 for their compressive strength, flexural strength, and permeability. The results showed that the 28-day compressive strength of foamed concrete increases with increasing density. It was also found that the pore size of foamed concrete increases with the increase in density, but these large pores are surrounded by smaller ones, and a good distribution of air-voids is maintained.