Hydration Mechanism of Solid Waste Gelling Materials Containing Semi-Dry Desulfurization Ash

This study investigated the feasibility of using semi-dry desulfurization ash (DA) in combination with blast furnace slag (BFS) to prepare gelling materials, aiming to improve the resource utilization of DA. The effects of DA dosage and mechanical grinding on the compressive strength and hydration mechanism of BFS-DA gelling materials were investigated. The results showed that the optimum BFS-DA ratio was 60:40, and the compressive strengths were 14.21 MPa, 20.24 MPa, 43.50 MPa, and 46.27 MPa at 3, 7, 28, and 56 days, respectively. Mechanical grinding greatly improved the activity of the gel materials, with the greatest increase in compressive strength at 3, 7, 28, and 90 days for the BFS and DA mixed milled for 30 min, with increases of 89.86%, 66.36%, 24.56%, and 25.68%, respectively, and compressive strength of 26.22 MPa, 35.6 MPa, 58.33 MPa, and 63.97 MPa, respectively. The cumulative heat of hydration of BFS-DA slurry was about 120 J/g. The hydration mechanism showed that the main hydration products formed were ettringite, C-S-H gel, AFm, and Friedel's salt. Calcium sulfite in DA was participated in the hydration, and a new hydration product, Ca₄Al₂O₆SO₃·11H₂O, was formed. DA can be effectively used to prepare BFS-based gelling materials, and its performance meets the requirements of GB/T 28294-2024 standard, which provides a potential solution for the utilization of DA resources and the reduction in the impact on the environment.