Comparative study on the performance of protein and synthetic-based foaming agents used in foamed concrete

Foamed concrete is a composite material with a density that is significantly lower than standard concrete. The property of being lightweight is due to tiny air voids produced by the addition of foaming agents in cement paste. The purpose of this research is to experimentally investigate the influence of various types of foaming agents i.e., protein versus synthetic-based foaming agents on the properties of foamed concrete. Foam stability, compressive strength, drying shrinkage of the foamed concrete specimen were experimentally studied and analyzed. Also, the characterization of the microstructure i.e. pores size and their distribution has been investigated in this study to gain insight into the impact of foaming agent on the properties of foam concrete. The study comprises 60 foamed concrete specimens cast using protein and synthetic-based foaming agents. The constituents of the concrete mix were kept uniform for both the cases and the quantity of foaming agents was increased from 30 to 112 kg/m3, this was done to produce foamed concrete of density varying from 600 kg/m3 to 1200 kg/m3. The foam stability and strength test depicted better results for protein-based foam rather than the synthetic-based foaming agent. The experimental results of the SEM analysis showed protein-based foamed concrete has unconnected isolated pores of smaller size, circular with a well-defined boundary as compared to synthetic-based. The compressive strength of both the foamed concrete had an increasing trend with a rise in density however the protein-based foamed concrete showed better results i.e., 13 % higher strength than synthetic-based foamed concrete at 1200 kg/m3 density, but an inverse trend in drying shrinkage with dry density was recorded. At low densities the shrinkage observed was less. The drying shrinkage of protein-based concrete was observed to be 29 % lower than the synthetic-based foamed concrete at the density of 1200 kg/m3. Hence this study reveals that the use of protein-based foaming agents would result in improved characteristics of foamed concrete.