This study investigates the effect of microwave treatment on the Cerchar abrasivity index (CAI) of igneous rocks such as granite, syenite, and gabbro. First the mineral contents and percentages of each rock were determined. Then, microwave treatment was applied on the specimens broken in the indirect tensile strength for 180s at the microwave powers of 2 kW and 6 kW. The evaluation of the test results shows that the CAI values of the specimens decrease with increasing microwave power. The CAI losses increase generally with the increasing surface temperature and the microwave power depending on the mineral contents. Concluding remark is that microwave treatment decreases the CAI values of igneous rocks. However, further study should be carried out to determine the CAI loss for different rock types at different exposure times and microwave powers.
The abrasivity may highly affect the cost and schedule of the projects performed in abrasive rock mass. If the rock is abrasive, the replacement of tools causes considerable downtimes in addition to the high cost due to the cutting tool wear. Therefore, the understanding of wear mechanism of cutting tools and various machine components is important for the planning and cost estimation of excavation projects.
Some researchers have investigated the effects of microwave treatment on the mechanical properties of rocks for possible application in the microwave assisted rock excavation to increase advance rate and decrease tool wear (Satish 2005, Satish et al. 2006, Motlagh 2009, Peinsitt et al. 2010, Nejati et al. 2012, Motlagh 2015, Hassani et al. 2016, Lu et al., 2017, Zheng et al. 2017). However, only one researcher (Motlagh 2009) has investigated the effect of microwave treatment of the abrasivity of rocks. He exposed different hard rocks to microwave illumination at a power level of 800-3000W for the durations ranging from 0 to 240s, and showed that Cerchar abrasivity index (CAI) of almost all tested samples showed a reduction of up to 30% depending on the applied microwave power and exposure duration.
