Experimental Study on Scour Resistance Performance Enhancement of Chongqing Red Clay

To effectively utilize Chongqing’s solid waste red clay for scour protection of local cross-river bridge foundations, this study modified Chongqing red clay using curing agent and cement, focusing on the effects of curing agent dosage, cement content, and water-to-solid ratio on the flowability, anti-dispersion performance, and scour resistance of solidified soil. Microstructural characteristics were observed via SEM, with formula fitting performed for two key parameters. Results indicate that an increased curing agent dosage significantly reduces flowability and suspended solids content of solidified soil while negligibly affecting critical shear stress; elevated cement content markedly enhances critical shear stress, slightly improves short-term flowability with reverse effects over time, and minimally impacts anti-dispersion performance; reduced water-to-solid ratio mitigates free water-induced cohesion weakening, lowering suspended solids content and flowability while increasing critical shear stress. Microstructural analysis reveals that generated C–S–H gels and ettringite (AFt) effectively fill pores, enhance matrix integrity, and improve scour resistance. A suspended solids content–flowability relationship model (R2 = 0.977) established through quadratic polynomial regression demonstrates excellent predictive performance. The optimal mix proportion (0.3% curing agent, 10% cement, 0.5 water-to-solid ratio) meets specifications and construction requirements, serving as the optimal solidified soil formulation for scour protection.