Preparation of Cement Mixture from Chromium-containing Steel Slag
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摘要: 采用钢渣处理含Cr3+废水,将吸附Cr3+后的钢渣用作水泥混合材,探讨了钢渣吸附Cr3+的效果,研究了含铬钢渣对水泥砂浆凝结时间、流动度、制品强度及水化性能的影响,分析了水泥固化Cr3+的机理。结果表明,钢渣能有效处理含铬废水,当废水的Cr3+浓度与pH值分别为40 mg/L与6,液固比为10∶1时,该钢渣的Cr3+吸附量与吸附率分别达5.93 mg/g与85.63%。引入含铬钢渣可提高水泥砂浆流动性能,但不利于改善制品的抗压强度。掺入32%的含铬钢渣可得到初凝时间、终凝时间及流动度分别为176、286 min与193.2%的水泥砂浆。养护7 d与28 d后,水泥制品的抗压强度达到了42.5R等级。XRD与SEM分析表明,钢渣水化活性低,提高钢渣的添加量不利于生成托勃莫来石、C-S-H及C-A-S-H等水化产物。Cr3+未与原料中的组分发生反应,它被无定型态的凝胶产物物理包裹是抑制其浸出活性的主要原因,在酸性环境下,样品的Cr3+浸出浓度均满足GB5085.3—2007标准。该研究为高效利用含铬钢渣提供了新的思路。Abstract: Steel slag is an industrial waste,and the efficient utilization of steel slag has important environmental value.In this paper,steel slag was used to treat wastewater containing Cr3+ and then used as cement mixture.The effect of steel slag adsorbing Cr3+ was discussed.The influence of steel slag containing chromium on setting time and fluidity of cement mortar were studied,and the effect of steel slag on strength and hydration performance of cement products was investigated too.The mechanism of cement solidifying Cr3+ was analyzed.The results showed that steel slag could effectively dispose of wastewater containing Cr3+.When the Cr3+ concentration and pH of the wastewater were 40 mg/L and 6,respectively,and the liquid-solid ratio was 10∶1,the adsorption capacity and adsorption rate of Cr3+ on the steel slag reached 5.93 mg/g and 85.63%,respectively.The introduction of chromium-containing steel slag improved the fluidity of cement mortar,but reduced the compressive strength of products.The initial setting time,the final setting time and fluidity of cement mortar were 176 min,286 min and 193.2% respectively,when 32 % chromium-containing steel slag was added.The compressive strengths of cement products could reach 42.5 R grade after curing for 7 days and 28 days.XRD and SEM analysis displayed that the low hydration activity of steel slag and the addition of steel slag were not conducive to hydration products formation such as C-S-H gels and tobermorite.Cr3+ did not react with other components in the raw material,and its cementation by amorphous calcium silicate hydrate was the main reason to inhibit its leaching activity.Under acidic condition,the Cr3+ leaching concentration meet the requirement by GB5085.3—2007 standard.This study provides a new way for the efficient utilization of heavy metal adsorption steel slag.
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