Thermal behaviors of cement and mortar under microwave treatment and the influencing factors: An experimental study

Microwave-assisted breakage of cementitious materials has emerged as a promising green and low-carbon method for dismantling cementitious structures. To understand the mechanism of microwave-induced cracking in structures, it is essential to study the thermal behaviors of cement and mortar under microwave treatment. In this paper, the effects of mixture ratio, water content, and microwave power on the microwave heating characteristics of cement and mortar specimens were investigated through real-time temperature and mass monitoring. In particular, the influence of microwave power on the bursting effect of cement and mortar specimens was analysed, and the mechanism of specimen bursting was explained. The results show that moisture content, water-cement ratio, and microwave power significantly impact the heating rate and mass loss of cement and mortar during microwave treatment. Based on the heating rate, the heating process of cement and mortar under microwave treatment can be divided into three to four stages, depending on the moisture content. The primary reasons for variations in the heating rate are water evaporation and the decomposition of hydrolysis products. The thin-wall ball model based on steam pressure theory can explain the bursting of cement and mortar specimens. Our findings suggest that increasing microwave power and water content in mortar specimens can lead to microwave-induced cracking.