Lightweight Foamed Concrete

In recent years, lightweight foamed concrete has gained popularity because of its thermal insulation properties and ease of production. However, this type of concrete has the drawback that it is highly unstable in its fresh state and exhibits high drying shrinkage when hardened. In this paper, we develop an improved foamed concrete mixture that can withstand these adverse phenomena. The experimental results of this mixture showed that its pore structure is strongly influenced by its dry density, which is mainly determined by the foam content. Hence, it is crucial to reduce the dry density of this material in order to improve its stability in its fresh and hardened states.

The optimum ratio of cement, foamed aggregate, and water was achieved by adjusting the concentration of a typical supplementary cementitious materials (SCM) such as fly ash, ground granulated blast furnace slag, and silica fume. The SCMs are incorporated in a varying range of proportions from 30 to 70 percent by volume. In addition to these SCMs, a specific foaming agent called GENFIL is added for the purpose of producing stable and homogenous cellular lightweight concrete.

The foamed concrete was produced using a wet method by utilizing static inline mixers with continuous on board density monitors to ensure the proper blending of the base and foamed aggregates. The resulting concrete was found to have a high water retention, a relatively low viscosity, and a strong thixotropic behavior, and it had a higher compressive strength at early ages than the control mix with cement alone. Moreover, the flexural strength was found to increase significantly with the inclusion of POFA, due to the formation of additional C-S-H gel by the pozzolanic reaction of this SCM.