Blasting remains the dominant rock fracturing method, yet its use is increasingly constrained by safety and environmental concerns. Soundless chemical demolition agents (SCDAs) offer a non-explosive alternative, yet conventional products are costly, rely on non-renewable raw materials, and require long fracturing times. Here, this study explored the use of two industrial wastes, calcium carbide residue (CCR) and drinking water sludge (DWS), to synthesize sustainable SCDAs (CCR-DWS SCDAs). CCR, which is rich in Ca-bearing phases, served as the precursor for CaO, the primary expansive component, whereas DWS provided Al-, Fe-, and S-bearing constituents that helped regulate the reaction process and improved the expansion performance. Results demonstrated that the optimal formulation (6% DWS and 30% water content) reached 37.11±1.42 MPa at 4 h and 50.45±2.55 MPa at 24 h, outperforming four commercial SCDAs. Microstructural characterization identified portlandite as the dominant phase responsible for crystallization-induced expansion. An appropriate DWS addition enhanced the expansive pressure by regulating the hydration kinetics, whereas excessive DWS suppressed the hydration reaction and impaired pressure development. Granite fracturing experiments further confirmed the superior efficiency, showing that the optimal CCR-DWS SCDA achieved crack penetration much earlier, within only 1.4 h at a borehole diameter-to-side length ratio of 1:5 and 8.8 h at 1:10, compared with 10.8 h and 18.8 h for the commercial SCDA. Fracture-surface characterization further revealed that the higher loading rate induced by the CCR-DWS SCDA produced smoother macroscopic fracture planes, supporting more controlled and predictable directional fracture propagation. Overall, this work establishes a waste-to-performance pathway for producing high-efficiency SCDAs with clear sustainability and engineering benefits.
Zhu et al. (Fri,) studied this question.