Sustainable alkali‐activated grouting material incorporating industrial solid wastes for ground and structural strengthening

Abstract Achieving simultaneous control of workability, setting behavior, and strength remains a fundamental challenge in the design of high‐performance grouting materials for structural and infrastructure applications. This study proposes a ternary alkali‐activated system incorporating red mud, blast furnace slag, and fly ash, and establishes a performance‐oriented design strategy for multi‐source precursor‐based grouts. Considering the potential effects of RM‐related alkalinity and fine particles, the RM/ b ratio was fixed at 0.30, while the activator composition was optimized to balance flowability, setting behavior, and compressive strength; however, long‐term efflorescence and dimensional stability require further investigation. It is demonstrated that the synergy between precursor composition and activator chemistry enables the co‐development of coexisting C‐(A)‐S‐H‐type and N‐A‐S‐H‐type gel products and C‐S‐H gel networks, which fundamentally governs the balance between fluidity and strength. The selected engineering‐grade mixtures achieved spread diameters of 340–373 mm and gel times of 26.52–46.69 min. Their 3‐ 7‐, and 28‐day compressive strengths reached 11.0–20.5, 13.1–22.9, and 16.5–30.7 MPa, respectively. The optimized grout showed filling and bonding capacity in the tested coarse‐grained granular medium, leading to a significant enhancement in load‐bearing capacity and structural integrity of grouted ground. These findings not only identify a viable pathway for valorizing red mud in cementitious systems, but also provide a basis for further developing alkali‐activated materials for void filling and auxiliary reinforcement in coarse‐grained media.