Efficient utilization of waste shield slurry and CDW fines to prepare eco-friendly controlled low-strength material

Shield slurry has not been effectively utilized due to its ultrafine clay particles and high water content. Controlled low-strength filling material (CLSM) provides a promising approach for efficient, large-scale utilization of shield slurry and construction & demolition waste (CDW) fines owing to its low requirement for raw materials However, incorporating shield slurry into CLSM brings challenges such as prolonged setting time, reduced flowability and mechanical performance. This study utilized waste shield slurry to adjust the yield stress and viscosity of CLSM, thereby increasing its flowability while reducing segregation and bleeding risks. Additionally, sodium lignosulfonate and recycled gypsum powder were introduced to disperse the ultrafine clay particles and reduce water demand, further accelerating setting and hardening and increased both early and later strengths. A series of shield slurry-CDW fines-based CLSMs with superior workability, low bleeding ratio, and adjustable strength was prepared. The maximum slurry substitution ratio reached 50 wt% of the CLSM. Furthermore, mix proportion design principles correlating CLSM workability and rheology were proposed. Compared to CLSMs utilizing industrial solid wastes, shield slurry-CDW based CLSM has a >50% reduction in cost and 80-86% reduction in natural resource consumption, offering significant economic and environmental benefits.