Evolution of the physical and mechanical properties of NPAG waste rock cores with respect to freeze-thaw and wet-dry cycles
To assess the durability of the NPAG waste rock unit with respect to freeze-thaw and wet-dry cycles, four physical and two mechanical properties were followed as rock cores were subjected to successive weathering cycles. The properties include the dry density, water absorption index, apparent porosity, mass loss, unconfined compressive strength (UCS), and Young's modulus. The mass loss was calculated based on a sample's initial oven-dried mass and final oven-dried mass. The physical properties were determined following ISRM suggested test methods (i.e., ISRM 1981).The dry density was determined using the caliper method; the water absorption index, or void index, was determined using the quick absorption technique; and the apparent porosity was determined using the saturation and caliper method. UCS tests were performed on dry samples following method C of the ASTM D7012-14e1 and using a Tinius Olson (200 tons capacity) servo-controlled press at a load rate of 1 kN/s. Young’s modulus was calculated based on the average modulus of the linear portion of the axial stress-strain curve obtained during the UCS tests. The high density, low water absorption index, and low apparent porosity of the fresh rock cores suggests an excellent rock durability. This durability is confirmed by the degradation tests, which show acceptable mass losses and negligible evolution of the material’s physical and mechanical properties with freeze-thaw and wet-dry cycles.