Thermal response and crack propagation of mineral components in olivine basalt under microwave irradiation

Microwave pre-treatment of mechanical rock breakage is an efficient technology to reduce bit wear and maintenance cost of the breaker. Thermal responses of basalt and its mineral components were tested using a multimode industrial microwave system. Different dielectric properties of the mineral components resulted in thermal stress within the basalt and hence crack propagation. Crack patterns of basalt after exposure were observed employing scanning electron microscope (SEM). Rock failure was induced by the unstable extension of radial cracks around the absorbing mineral grain boundary. A novel theoretical model containing initial micro cracks was established to investigate crack propagation behavior under microwave irradiation. A characteristic radius of cracks existed where the microwave energy required for crack growth was minimum. Cracks with radius shorter than characteristic radius would propagate in a kinetic manner. Most of the damage concentrated in an optimum exposure time range at the given power might be explained by the kinetic propagation of micro cracks.