The influence of microwave treatment on the compressive and tensile strength of igneous rocks

Abstract

Cutting hard rocks has some problems such as low penetration rate and high wear rate of cutting tools. These problems can be solved by the microwave treatment of hard rocks during cutting. In this study, the effects of microwave treatment were investigated on the strength of nine different igneous rocks. First, the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests were carried out on the untreated samples. Then, the strength tests were performed on the microwave treated specimens. The results show that the rock strength decreases generally with increasing microwave power and treatment duration. The strength losses and the heating degrees are different for each tested rock type irradiated by microwave power due to the different the mineral content. When treating the specimens with microwave energy, crackings and/or meltings occur depending on the applied power, the exposure duration, and the mineral content. Even a small amount of metallic mineral can increase too much the temperature of a specimen. The UCS and the BTS values of granites decrease generally with increasing surface temperature after 200 °C and 100 °C, respectively. The significant losses in the UCS and the BTS values of syenite and gabbro specimens are generally observed below 100 °C due to their metallic mineral contents or high amount of microwave absorber minerals. It can be concluded that microwave irradiation has important influences on the strength of igneous rocks depending on the applied energy, the exposure time, and mineralogy.