Effects of foaming agent type on the workability, drying shrinkage, frost resistance and pore distribution of foamed concrete

Aiming to explore the effects of the foaming agent type on the properties of foamed concrete, synthetic surfactants (SS), plant surfactants (PS) and animal glue/blood based surfactants (AS) were used to produce foamed concrete with a density of 600 kg/m3. At this density, the structure and properties of foamed concrete were greatly influenced by the foaming agent type. The FTIR results show that the functional groups of SS, PS and AS are similar. However, the stability and strength of the foam made by SS are much higher than that of AS and PS, which may be due to the higher density and viscosity of SS foam. The experimental results exhibited that the compressive strength of foamed concrete with SS is 11% and 43% higher than that of foamed concrete with AS and PS, respectively. The drying shrinkage of foamed concrete with SS is 13% and 21% lower than that of foamed concrete with AS and PS, respectively. The pore structure of foamed concrete was tested with X-CT and Hardened Concrete Bubble Analyzer. Foamed concrete with SS showed narrower pore size distributions and fewer connected pores compared with the other two, which accounted for the high compressive strength, low drying shrinkage and strong frost resistance of foamed concrete with SS.