Evaluation of slake durability for carbonaceous rocks exposed to water soaking using electrical resistivity

The present study investigated the electrical conduction and slake durability behaviors of carbonaceous rocks subjected to water soaking. Several series of electrical resistivity and slake durability tests were conducted on carbonaceous rocks with different mineralogical characteristics to explore the intrinsic connection between these two property indexes. Based on the experimental data, a new empirical model was developed to estimate slake durability index of carbonaceous rocks at varied soaking times. The results showed that the clay minerals content of investigated carbonaceous rocks ranged from approximately 20 % to 50 %. The clay minerals are beneficial in enhancing the electrical conduction of carbonaceous rocks, but impose a negative impact on the slake durability, attributing to their superior performance of hydrophilicity and swelling. Electrical resistivity decreased sharply with increasing soaking time within the first 8 days and then it achieved a stable state as soaking time further increased, which was mainly due to the completion of pore saturation and salts/minerals dissolution. The slake durability index exhibited similar evolution characteristics to those of electrical resistivity, which deteriorated sharply to a low or very low level after soaking for 16 days. The clay minerals experienced water absorption and mineral expansion during the first 8 days soaking, leading to the development of micro-cracks that facilitates water intrusion and accelerates the slake durability deterioration. These two processes were essentially complete as the soaking time further increased, and the clay minerals played an insignificant role at this stage. Liner increasing trends were observed in the plot of electrical resistivity decrease versus slake durability index decrease, and the slope values presented a power function relation with the clay minerals content of carbonaceous rocks. The proposed empirical model well captured the trends in the experimental data, with an absolute difference in percentage δ below30 % and a root mean square error RMSE value of 5.613 %. The outcomes of this study provided a viable answer to assess slake durability of carbonaceous rocks exposed to adverse external environments using non-destructive testing techniques.