New Type of Super-Lightweight Magnesium Phosphate Cement Foamed Concrete

Most previous investigations on foam concrete have been confined to portland cement and the density range of $400–\mathrm{1,600}\mathrm{kg}/{\mathrm{m}}^3$. The present study aims to develop a new foam concrete with a density ranging from 250 to $400\mathrm{kg}/{\mathrm{m}}^3$ by replacing portland cement with magnesia phosphate cement (MPC). Extensive laboratory tests were performed to characterize the fresh properties, strength, water resistance, and thermal conductivity of the MPC foam concrete. In the experimental studies, mixtures were prepared by replacing fine sand with various contents of fly ash. The results show that an appropriate workability value is achieved at a water-solid ratio of 0.30, at which a foam concrete mixture with a good stability and consistency can be produced. Using fly ash to replace fine sand can improve the properties of MPC foam concrete, includings its compressive strength, water resistance, and thermal conductivity. Novel super-lightweight foam concretes with dry densities ranging from 210 to $380\mathrm{kg}/{\mathrm{m}}^3$ were produced, with strengths ranging from 1.0 to 2.8 MPa and thermal conductivities ranging from 0.049 to $0.070\mathrm{W}/\mathrm{m}·\mathrm{K}$.