Experimental Research on the Performance of All-Solid-Waste Cementitious Grouting Filling Materials

Overburden bed separation grouting is a green mining method to control surface subsidence and protect surface buildings (structures). The performance of cementitious grouting material is the key factor affecting grouting filling. Although offering good fluidity and low cost, the fly ash (FA) slurry demands a significant water supply, undergoes high dehydration rates, and lacks cementing property. These factors result in low grouting efficiency and negatively impact the safety of operations in complex-structure areas. This work developed a CBF + D series all-solid-waste cementitious grouting filling material with blast furnace slag (BFS), FA, carbide slag (CS), desulfurization gypsum (DG), and calcium chloride (CaCl2) as components. Based on the orthogonal test, the basic performance test of the grouting material was carried out using macroscopic and microscopic test methods. The influences of the water-cement ratio, the mass ratio of BFS to FA, the proportion of CS, and the proportion of DG on the slurry density, fluidity, water extraction rate, and uniaxial compressive strength (UCS) of the stone body were assessed. The material's hydration mechanism was analyzed by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) microscopic experiments. The optimal parameters for this test were as follows: a water-cement ratio of 0.7, a mass ratio of BFS to FA of 3:1, a proportion of CS of 40%, and a proportion of DG of 4%. Under the optimal conditions, the density of the slurry was 1.41 g<middle dot>cm-3, with a fluidity of 15.7 cm, a water extraction rate of 0.107, and a UCS of the stone body of 6.25 MPa. The water extraction rate of the slurry is 67% lower than that of the FA slurry and the slurry has good cementation performance, while still maintaining its fluidity. This significantly enhanced the safety and applicability of the grouting filling process. In addition, CBF + D series all-solid-waste cementitious materials have solved the large accumulation of industrial wastes such as FA, BFS, and CS, which maximized the resource utilization rate of these wastes and brought significant economic benefits.