Microwave-induced damage evolution in concrete under electromagnetic-thermo-mechanical coupling effects

In this article, a numerical simulation of the electromagnetic-thermo-mechanical-damage coupling effects of concrete damage under microwave irradiation was conducted. The variation and evolution of electromagnetic and temperature fields were analyzed firstly. Then, the mechanical-damage coupling analysis was performed to further investigate the distribution of internal stress and damage evolution mechanisms in the concrete. The results indicated that the dielectric properties of aggregate contribute to the significantly high electromagnetic losses, leading to rapid heating of aggregate and the formation of a temperature gradient at the aggregate–mortar interface. Under the combined effect of the temperature gradient and thermal stress, the stress concentration at the interface was more obvious, identifying it as the critical region for damage initiation and propagation. Furthermore, electromagnetic and temperature field uniformity are the core factors determining the aggregate–mortar separation efficiency; under 4 kW microwave irradiation, the overall stripping rate reaches 25.4%, whereas it exceeds 35.4% in the high electromagnetic field strength region. These findings indicate the mechanism of microwave-induced concrete fracturing and suggest the importance of optimizing the electromagnetic field distribution.