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

摘要：

钢渣安定性处理过程常常造成胶凝活性的损失。为此，本文利用改性助剂消除钢渣水化过程中产生的氢氧化物并生成胶凝产物，在蒸压建材的生产过程中实现钢渣安定性处理和游离氧化物的活性化利用，并避免单独处置钢渣造成的活性物质损失。研究表明，8%秸秆灰和3%磷酸二氢铵作为复合助剂制备的尾矿-钢渣蒸压试块体积稳定，抗压强度达24.0MPa。通过对蒸压样品游离氧化物消解率、化学结合水量及热重、XRD分析，得出钢渣安定性处理与活性化利用机制：硅质材料与钢渣中f-CaO水化生成的Ca(OH)₂结合迅速生成对体系力学强度有益的水化硅酸钙，避免因大量Ca(OH)₂积累造成体积膨胀；磷酸盐中的NH₄⁺、H₂PO₄^-与f-MgO结合生成磷酸铵镁及其他低溶度积复盐类矿物，进而消除因f-MgO水化生成Mg(OH)₂造成体积膨胀的隐患。试样在180℃蒸压4h后，f-CaO及f-MgO消解率分别可达86.28%、89.73%。本文将为利用钢渣大比例取代水泥和石灰生产蒸压建筑材料提供理论基础，对于提高钢渣利用率、减少碳排放具有重要价值。

关键词: 钢渣, 蒸压, 安定性, 游离氧化物, 水化硅酸盐