Mechanical responses of igneous rocks to microwave irradiation: a review

The Comminution of Chert Gravel by Microwave Irradiation

“…Our results show that an increase in irradiation time decreases the strength of chert gravel, which is similar to previous results, e.g., [8,11,20,[42][43][44].…”

“…Extensive laboratory experiments [44] performed with three types of rocks (norite, granite, and basalt) showed that tensile and uniaxial compressive strengths experienced a reduction with prolonged exposure time and higher power levels of microwave irradiation. It was demonstrated that stress and damage increased with higher power density, resulting in lower sample strength, while reducing exposure time (for a given energy input) leads to more significant strength reductions [8,11]. This conclusion is consistent with the results presented in [45], where it was shown that the tensile strength of granite and cement mortar decreased in proportion to the duration of microwave pre-treatment.…”

“…The analysis of the experiments' results shows that despite quartz's weak response to microwave irradiation noted in [11,22,23], this method can significantly weaken chert gravel (Table 2). The mean temperature on the sample surface (Table 1) aligns with the values presented in [17,18] for a significant number of rocks.…”

“…The data presented in [10] highlight the prospective use of microwave energy in various mineral treatment and metal recovery procedures, including heating, drying, grinding, leaching, roasting, smelting, carbothermic reduction of oxide minerals, pre-treatment of refractory gold concentrate or ore, spent carbon regeneration, and waste management. It has been established that beyond a certain threshold, power density has a minimal impact on irradiation time and energy consumption [11]. It was noted that larger crystals demand less time and energy for significant alterations in the mineral state [12].…”

“…Examining microcrack growth in galena and calcite ore particles under microwave irradiation indicated that mineral shape predominantly impacts microcrack quantity but not their growth behavior [24]. Numerous studies have explored the effect of temperature increase on rock properties [11,12,22], including static and dynamic mechanical properties, e.g., strength, elastic modulus, elastic wave velocity [25][26][27][28][29][30][31][32][33][34], fracture toughness, porosity, and micro-fracturing [34][35][36][37][38][39][40]. Studies on basalt revealed significant microcrack differences based on power levels and distances from the antenna, with longer exposures leading to more severe cracks [41].…”