Experimental study on the preparation and properties of a novel foamed concrete based on magnesium phosphate cement

The long setting time of conventional OPC-based foamed concrete usually hinders the next step of constructions. Based on the unique advantages of magnesium phosphate cement (MPC), a novel foamed concrete with the characteristics of quick setting and high early-strength is prepared by using sodium bicarbonate (NAC) as a foaming agent in this study. In order to investigate the mechanical and physical properties systematically, the 3-h and 28-day compressive strength, splitting tensile strength, thermal conductivity and water resistance are measured during the experiments. The laboratory results indicate that the dry density, compressive strength, splitting tensile strength, thermal insulation and water resistance decrease as increasing the NAC content. It is notable that the 3-h compressive strength of MPC-based foamed concrete is about 70% of the 28-day compressive strength. The relationships of the modulus of elasticity and splitting tensile strength to compressive strength are analyzed by power functions. And a linear function is suitable to describe the reduction in strength retention coefficient with the increase of the water absorption. The compressive strength and water resistance of MPC-based foamed concrete with a target density of 550 kg/m3 can be improved by adding the predetermined amount of fly ash. And the 28-day compressive strength and thermal conductivity of MPC-based foamed concrete with 10% fly ash are 2.4 MPa and 0.072 W/mK, which are superior to those of OPC-based foamed concrete with the same dry density.