Investigating the effects of microwave treatment on the Cerchar abrasivity for igneous rocks

Despite the significant advances in rock excavation technologies, the excavation of hard and abrasive rocks has still some problems such as low penetration rate and high tool wear. Especially in the abrasive rock excavation, in addition to the high cost, the tool wear result in low advance rate due to downtimes during the replacement of tools. Therefore, the reduction of cutter wear is important in terms of excavation technology. One of the most common methods used to measure rock abrasiveness and to estimate cutter consumption is the Cerchar abrasiveness test. In this thesis, the effects of microwave treatment on the Cerchar abrasivity of magmatic rocks were investigated. First, Cerchar abrasion tests were performed on the 9 different magmatic rocks (granite, syenite and gabbro) without microwave treatment. Then, Cerchar abrasivity experiments were repeated on the samples exposed to microwave irradiation at 2 kW and 6 kW for 180s. After that the Cerchar abrasivity values of the untreated and treated by microwave were compared. It was seen that the treatment by microwave decreased the abrasivity values. It was found that there was an inverse relation between the applied microwave power and the abrasiveness index for the tested rocks. Moreover, considering the fact that the degree of influence of microwave energy on the rocks depends on the mineral content of the rock, the obtained results were evaluated by taking into consideration the mineralogy of the samples. It was observed that even if the percentages of metallic minerals in a rock sample are too low (2% magnetite, 3% pyrite), they increase the temperature of the rock (~900 °C) and decrease its abrasivity (~60%). Concluding remark is that microwave treatment has important effect on the abrasivity of igneous rocks depending on the applied power and exposure duration.