Experimental investigation on the compressive strength of foamed concrete: Effect of curing conditions, cement type, foaming agent and dry density

This paper presents the first results of an ongoing experimental campaign focused on foamed concrete. The dependence of the compressive strength upon dry density, water content, curing conditions, cement type and, most importantly, foaming agents employed in the cement paste is here investigated. In particular, this experimental study comprises more than 100 foamed concrete specimens with a fixed water/cement ratio and dry densities ranging from around 350 up to 850 kg/m3, two cement types, three foaming agents with either protein or synthetic nature, and curing conditions in water at 30 C, in air as well as within a cellophane sheet at environmental temperature. Unlike most of the research studies in which the water/cement ratio is adjusted on the basis of the stability and the consistence of the foam concrete mix, in this experimental investigation this ratio is fixed constant for all the analyzed design densities. This specimen preparation has made it possible to highlight different behaviors of the employed foaming agents having different nature, which is not fully described in other similar studies of the relevant literature, especially for the range of low densities analyzed in this work. The variability of the compressive strength measured is ascribed to a different stability behavior of the foams generated by foaming agents having different nature during the mixing phase with the cement paste. It is found that the increase of the compressive strength with the density is more or less described by a linear trend and is more pronounced when protein foaming agents are employed in the mix design.