Microwave heating and fracturing of concrete with different aggregates: An experimental and numerical study

This study evaluated the effects of aggregate types on microwave heating characteristics of concrete and verified the feasibility of microwave-induced concrete fracturing through experiments in both multi-mode cavity and open-ended irradiation settings. Additionally, numerical simulations were employed to elucidate the fracturing mechanism of concrete under microwave irradiation. Results indicate that the microwave sensitivity of coarse aggregates significantly influences the heating characteristics of concrete. The dielectric properties of coarse aggregates are minimally affected by temperature, allowing them to maintain stable heating rates during microwave exposure. Prolonged microwave irradiation leads to crack formation between coarse aggregates and mortar, facilitating moisture escape and further deteriorating the cracked areas. In open-ended irradiation experiments, sample damage increased with microwave input energy, with high-power, short-duration irradiation proving more conducive to concrete fracturing than lower-power, longer-duration treatments given equivalent energy inputs. Under open-ended irradiation, concrete fracture primarily results from thermal expansion underneath the waveguide, inducing circumferential tensile stress.