关键词: 钢渣, 蒸压, 安定性, 游离氧化物, 水化硅酸盐

Abstract:

The stability treatment of steel slag often leads to the loss of cementitious activity. Therefore, the modified additives were used to eliminate the hydroxides produced in the hydration process of steel slag and generate cementitious products, so as to realize the stability treatment of steel slag and the active utilization of free oxides in the production of autoclaved building materials, and avoid the loss of active substances caused by the separate disposal of steel slag. The results showed that the autoclaved tailings-steel slag samples produced with 8% straw ash and 3% ammonium dihydrogen phosphate as modifier had a stable volume with compressive strength of 24.0MPa. The digestion rate of free oxides, the amount of chemically bound water, thermogravimetry and XRD analysis were performed for the samples, and the stability treatment and activation mechanism of steel slag was proposed: the siliceous material combines with the Ca(OH)₂ generated by the hydration of f-CaO in the steel slag to quickly generate C—S—H, which is good for the mechanical strength of the system, avoiding the volume expansion caused by the accumulation of Ca(OH)₂; NH₄⁺ and H₂PO₄^2- in phosphate combines with f-MgO to generate magnesium ammonium phosphate and other low-solubility complex salts, thereby eliminating the hidden danger of volume expansion caused by f-MgO hydration to generate Mg(OH)₂. After the sample was autoclaved at 180℃ for 4h, the digestion rates of f-CaO and f-MgO could reach 86.28% and 89.73%, respectively. This technology will provide a basis for the production of autoclaved building materials by using steel slag to replace cement and lime in a large proportion, and is of great value for improving the utilization rate of steel slag and reducing carbon emission.

Key words: slag, autoclaved, stability, free oxides, hydrated silicate