The Performance and Mechanism of Modified Magnesium Phosphate Cement Utilizing Bottom Ash from Municipal Solid Waste Incineration after High-Temperature Treatment

To investigate the performance of magnesium phosphate cement (MPC) after high-temperature treatment and the comprehensive utilization of bottom ash (BA) from municipal solid waste incineration, performance tests and microscopic mechanism analyses were conducted on BA-modified MPC treated at various temperatures. The results indicate that the mass loss of MPC was most significant at 105°C, and stabilized at 600°C. Both flexural strength and compressive strength exhibited a trend of initially decreasing and then increasing with rising temperature. However, at the same temperature, the flexural strength and compressive strength of MPC first increased and then decreased as the dosage of BA increased. At 1,000°C, the compressive strength of BA-modified MPC ranged from 17.64 to 28.08 MPa, surpassing that of unmodified MPC. The primary hydration product of MPC at 20°C was MgKPO4·6H2O; at 105°C, MgKPO4·6H2O dehydrates to form MgKPO4·H2O. The main decomposition product at 600°C–1,000°C was MgKPO4. At 1,000°C, Mg2SiO4 was detected in the product of BA-modified MPC, which may explain why BA enhanced the strength of MPC after high-temperature exposure. After high-temperature treatment, the pore structure of MPC gradually evolved from micropores to macropores, and the porosity increased. The established porosity evolution characteristic formula can accurately predict the porosity changes of MPC at different temperatures.