XRD与SEM的钢渣尾渣物理激发机理研究

钢渣是冶金工业中产生的主要固体废弃物，其产量约为每年粗钢产量的15%~20%。由于技术的局限，导致我国钢渣利用率较低，仅为年钢渣产量的10%；同时加之管理制度的不健全，导致钢渣大量露天堆放，对土地资源、地下水源，以及空气质量造成严重影响。固体废弃物再利用是资源可持续发展的重要途径之一，由于钢渣的主要化学成分(CaO，SiO₂，A1₂O₃，MgO，Fe₂O₃，MnO，f-CaO等)、主要矿物组成(硅酸三钙、硅酸二钙、钙镁橄榄石、钙镁蔷薇辉石、铁酸二钙等)与水泥熟料的主要化学成分、主要矿物组成极为相似，是一种具有潜在胶凝活性的胶凝材料。以钢渣尾渣作为研究对象，采用机械研磨的方式对钢渣尾渣处理，即物理激发，获得不同粒径钢渣尾渣微粉。依据《用于水泥和混凝土中的钢渣粉》(GB/T 20491-2006)与《水泥胶砂强度检验方法(ISO法)》(GB/T 17671-1999)制备一系列钢渣尾渣胶砂试块(分别标记为A₄₀，A₆₀，A₈₀，A₁₀₀和A₁₂₀)。研究对钢渣尾渣胶凝活性的影响，以及不同水化时间对钢渣尾渣胶凝活性的影响，即3 d钢渣尾渣胶砂强度、7 d钢渣尾渣胶砂强度与28 d钢渣尾渣胶砂强度。利用激光粒度分析仪(LPSA)对钢渣尾渣微粉的粒径分布进行测试与分析，X射线衍射仪(XRD)对钢渣尾渣微粉与钢渣尾渣胶砂的矿物组成进行测试与分析，扫描电子显微镜(SEM)进行微观形貌测试与分析，从而获得钢渣尾渣的物理激发机理。结果表明，随着钢渣尾渣微粉粒径的减小，其胶凝活性呈现先增加后降低的趋势，当研磨时间为80 min时，A₈₀钢渣尾渣微粉的胶凝活性最高，即3 d活性指数为67.55%、7 d活性指数为71.96%和28 d活性指数为73.61%。随着钢渣尾渣微粉粒径的减小，钢渣尾渣微粉中RO相的XRD特征峰强度稳定，Ca₂SiO₄与Ca₃SiO₅的XRD特征峰强度呈现先增加后降低的趋势，Ca₃SiO₅与Ca₂SiO₄参与水化反应，生成一定量的Ca(OH)₂与C-S-H凝胶，具有良好的胶凝活性。A₈₀钢渣尾渣微粉中Ca₂SiO₄含量较少，而Ca₃SiO₅含量较多，均可以生成一定量的Ca(OH)₂与C-S-H凝胶，小幅提高A₈₀钢渣尾渣胶砂的早期(3~7 d)力学性能，大幅提高A₈₀钢渣尾渣胶砂的中、后期(7 d~28 d)力学性能。当水化时间3 d时，A₈₀钢渣尾渣胶砂中存在少量水化产物且大量分散小颗粒；当水化时间7 d时，A₈₀钢渣尾渣胶砂中水化产物大幅增加且形成较大颗粒；当水化时间28 d时，A₈₀钢渣尾渣胶砂中形成大量水化产物且几乎不存在分散小颗粒。从而进一步实现固体废弃物的资源化再利用，达到钢铁企业增加效益，环境缓解压力的目的。

Study on Physical Excitation Mechanism of Steel Slag Tailings by XRD and SEM

Steel slag tailings are the main solid waste in metallurgical industry, with the production of 15%~20% of crude steel. The utilization ratio is quite low and only reaches 10% of steel slag tailings production due to limited technology. Meanwhile, steel slag tailings are disposed by direct stacking and landfill in general since the management system is not perfect, which pollutes land source, underground water source and air quality. Recycling of solid waste is one important method to achieve sustainable development of resources. The main chemical composition, i. e., CaO, SiO₂, Al₂O₃, MgO, Fe₂O₃, MnO, f-CaO, etc. and mineral composition, i. e., tricalcium silicate, dicalcium silicate, monticellite, dicalcium ferrite, etc. of steel slag tailings are almost similar to that of cement clinker, making them as the cementitious material with potential cementitious activity. In this paper, steel slag tailings were stimulated physically by mechanical grinding to obtain powder with various sizes. Then, mortar samples of steel slag tailings were prepared in light of Steel slag powder used for cement and concrete (GB/T 20491-2006) and Method of testing cements-Determination of strength (ISO) (GB/T 17671-1999). Then, the impact of steel slag tailings powder at different size, i. e., A₄₀, A₆₀, A₈₀, A₁₀₀ and A₁₂₀, on cementitious activity was investigated experimentally, as well as the impact of hydration time on cementitious activity, namely at 3, 7 and 28 d. After that, the size distribution of steel slag tailings powder was characterized by LPSA, and mineral composition and steel slag tailings mortar were tested by XRD and microstructure of steel slag tailings mortar was tested by SEM in order to obtain physical excitation mechanism of steel slag tailings. The results showed that the cementitious activity of steel slag tailings powder presented an increasing trend followed by a decreasing trend as size of steel slag tailings powder decreased. When grinding time was 80 min, the maximum activity occurred at A₈₀. The activity index showed as 67.55%, 71.96% and 73.61% for 3d, 7 and 28 d respectively. As the powder size decreased, the characteristic peak of RO phase in XRD analysis kept a steady intensity while characteristic peak intensity of Ca₂SiO₄ and Ca₃SiO₅ increased first but decreased afterwards. The hydration reaction of Ca₃SiO₅ and Ca₂SiO₄ could generate Ca(OH)₂ and C-S-H gel with good cementitious activity. Small amount of Ca₂SiO₄ could be found in A₈₀ steel slag tailings powder while large amount of Ca₃SiO₅ existed, both of which could be used to generate Ca(OH)₂ and C-S-H gel. They can improve the mechanical property of A₈₀ steel slag tailings mortar slightly at early period of 3~7 d but greatly at later period of 7~28 d. When hydration time reached 3 d, small amount of hydration products and many micro particles existed in A₈₀ steel slag tailings mortar. For 7 d, the abovementioned hydration products increased to a great extent and larger particles formed. At 28 d, lots of hydration products were generated and there was rarely dispersed micro particles. Under this condition, recycling of solid wastes could be accomplished so as to increase benefit and would not pollute environment severely any more.