Mechanical performance and mechanism of incineration bottom ash-calcium carbide residue treated subgrade materials

In this study, soil volumetric substitution by incinerator bottom ash (IBA) and lime replacement by calcium carbide residue (CCR) were recycled as the sustainable subgrade materials, where the laboratory- and onsite-scale investigations were conducted to understand the road performance and its mechanism. The 30%IBA-6%CCR stabilized soil (C6I30) exhibits higher maximum dry density but lower optimum moisture content as compared to 6% CCR stabilized soil (C6I0). At the 96% compactness, the C6I30 has higher unconfined compression strength of 1.2 MPa, California bearing ratio of 52% and resilient modulus of 75 MPa. This is attributed to the synergistic infilling and interlocking effect of fine soil and CCR particles with rough-porous IBA particles, leading to higher compactness, and thus higher strength. Additionally, the active Si/Al component from IBA promote pozzolanic reaction. The findings, including the onsite pilot verification, provide the binary solid waste recycling approach in sustainable subgrade engineering.