Cracking behavior and bond deterioration of the mortar-aggregate interface under microwave heating

Microwave-assisted aggregate recycling from waste concrete is an innovative technology characterized by high efficiency, low energy consumption and environmental friendliness. This study experimentally investigates the cracking behavior and mechanical properties of the mortar-aggregate interface under microwave irradiation. The effects of different heating powers and heating time on the interfacial shear strength and splitting tensile strength were examined . The temperature evolution, interfacial crack propagation , and failure characteristics are systematically analyzed. The influence of microwave parameters and input energy on interfacial mechanical properties is evaluated. The results indicate that the cracks first appear at the mortar-aggregate interface. They propagate along the interface and then extend into mortar perpendicular to the interface with the irradiation time increase. The length and width of cracks perpendicular to the interface are smaller than those of the interface cracks. The interfacial strength, stiffness and fracture energy decrease linearly with the increase of microwave input energy. Under the same input energy conditions, high-power short-term heating will cause more severe interface degradation. After 200 kJ of microwave energy input, the interfacial shear strength is reduced to 50%, and the interfacial shear stiffness is reduced to 80%. The reduction in interfacial tensile strength is even more significant. This study elucidates the debonding mechanism of the mortar-aggregate interface after microwave irradiation. The findings provide a valuable reference for further research and industrial application of microwave-assisted technology for aggregate recovery from waste concrete.