Mechanical, damage, and fracture behavior of sustainable pavement composites from mining tailings and crushed stone waste: Effects of aggregate content under compression and splitting via AE, DIC, and CT

With the objective of repurposing multisource mining solid waste as sustainable pavement composites, this study investigates the effects of crushed stone aggregate content (CSAC) on the mechanical, damage, and fracture behavior of cemented tailings-crushed stone composites (CTCSC). Eight sample groups with CSAC values ranging from 0% to 100% are tested using a uniaxial compression test (UCT) and a Brazilian splitting test (BST), combined with AE, DIC, and CT monitoring. The results reveal nonmonotonic variations in uniaxial compressive strength (UCS), splitting tensile strength (STS), and the tensile-to-compressive strength ratio (T/C), which initially decrease, then increase, and finally decrease slightly at high CSAC levels. The elastic modulus reaches a maximum of 118.70 MPa at 90% CSAC. With increasing CSAC, the CTCSC exhibits a ductile-to-brittle transition in the UCT and a shift from concave deformation to near-linear prepeak deformation in the BST. AE activity remains low before the peak stress but increases sharply after failure, with tensile signals dominating the RA–AF characteristics. The global b-value peaks at 15% CSAC and then decreases, whereas the crack initiation stress reaches its maximum at 45% CSAC before declining. In the UCT, four failure modes are observed: shear (0%), tensile (15–30%), tensile–shear (45–60%), and shear–tensile (75–100%). The BST reveals three tensile failure patterns, namely, central (0%), deflected (15–60%), and stepped interface-induced (75–100%), with cracks initiating at the loading end. The crack opening displacement peaks at 1.860 mm before it decreases, whereas the crack tortuosity steadily increases. These findings elucidate the failure mechanisms of CTCSC and provide guidance for optimizing sustainable pavement composites using mining solid waste.