Preparation of a Novel Solid Waste Gel Material Using an Activation System of Alkali-Activated Slag and Phosphorus Tailings for Dolomitization

Abstract Phosphate tailings are commonly used as inert aggregates, but they face the challenges of low added value and low resource utilization efficiency. This study utilizes industrial solid waste, including phosphate tailings, blast furnace slag, and alkali, to construct an alkali activation and dolomitization system for the preparation of gel materials. Through the synergistic interaction of OH − , SiO 4 4 − , and AlO 3 3 − ions provided by the alkali and blast furnace slag, and Ca 2 + and Mg 2 + ions introduced by the phosphate tailings, a novel alkali activation and dolomitization synergistic activation effect is formed, which promotes hydration reactions. The formation of hydrated products such as layered double hydroxides (LDH), C─(A)─S─H, and so on, leads to the aggregation of these products, resulting in a new phosphate tailings–based cementitious material. When the phosphate tailings content is 50%, the 3- and 28-day compressive strength is 21.76 and 62.50 MPa, respectively, which meet the strength requirements for P · O 62.5 cement. The macroscopic properties of this gel material were systematically evaluated through setting time, and compressive strength tests of samples with different proportions of slurry. Additionally, X-ray diffraction (XRD), thermogravimetric (TG)-derivative thermogravimetry (DTG), Fourier transform infrared spectroscopy (FTIR), Si 29 magic-angle spinning (MAS) nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS) analyses were conducted to provide a comprehensive evaluation and elucidate the hydration process.