Effect of air content on the rheology of foamed concrete

Abstract

Foamed concrete is a lightweight concrete produced by the incorporation of foam into cement paste or mortar. This research was carried out to investigate the effect of foam content on standard workability tests results and also the rheological parameters of foam concretes. As previous studies on this topic were mainly limited to air contents of up to about 40%, the present study considered mixes with up to 91% air content in order to provide information regarding foam concretes of low densities. The results of rheological measurements show an increase in yield stress due to foam incorporation, and the effect is intensified with increasing foam contents. With regard to plastic viscosity, the results show that incorporation of moderate foam volumes results in a reduction in the plastic viscosity of the mixes. However, further increases in foam contents result in a reversal of the trend and plastic viscosities are substantially increased at high foam volumes. The results are significant, as they show a serious reduction in the workability of foam concretes at high air contents.