Sustainable Grouting Material from Industrial Waste: Multi-Performance Optimization via the Entropy-Weighted Taguchi Method and Its Environmental Implications

This work develops a sustainable, low-viscosity grout material by incorporating industrial byproducts (rice husk ash, RIA; and fly ash, FLA) to address key challenges in rock stabilization: clogging susceptibility, high cost, poor environmental performance, and unbalanced engineering properties. Through single-factor experiments and an entropy-weighted Taguchi–grey relational analysis, the optimal mix ratio was determined to be 10% RIA, 10% FLA, and 0.45% polycarboxylate superplasticizer (POS), and a liquid-to-solid ratio of 1.05. Improved workability: The viscosity of the slurry significantly decreases, allowing its injection into rock fissures as small as micrometers. The slurry setting time and strength meet the requirements for the emergency repair of engineering rock masses. Cost efficiency: Utilizing waste materials reduces production costs by 17.9% per ton. Environmental benefits: CO2 emissions decrease by 36.3% (150.62 g/kg vs. 237 g/kg for conventional grout), whereas leaching tests confirm that heavy metal concentrations (As < 0.1 ppm, Pb < 0.5 ppm) comply with environmental standards. Microstructural analysis reveals that RIA enhances density through pore-filling effects and pozzolanic activity. This study provides a practical, eco-friendly solution for rapid rock stabilization, aligns with circular economy principles, and supports sustainable infrastructure development.