建筑垃圾骨料浸出重金属对环境影响研究

为了探究建筑垃圾骨料作为渗透性路面底基层替代材料的适用性,必须考虑建筑垃圾对地下水的污染问题。选取2种常见的建筑垃圾再生骨料:再生砖骨料(CB)和再生混凝土骨料(RCA),探究其浸出重金属浓度含量及其污染物的释放特征及规律,分析建筑垃圾试样配比、液固比、pH 值等因素对重金属浓度的影响。结果表明:在纯砖块条件下时,重金属Cd、Cu、Ni和Zn含量最小;在纯混凝土条件下时,重金属Cr和Pb含量最小。Cd和Zn的含量随着液固比的变化上下起伏不大,浸出浓度基本保持不变,可见Cd和Zn达到了溶解平衡;Cr和Pb的浸出率随着液固比的增加而增加,浸出量也在不断增加;Cu和Ni的浸出率随着液固比的增加而减小。Cd、Ni和Pb在不同pH值时的浸出浓度随时间变化趋势也基本相似,随着pH值的升高,Cd、Ni和Pb的平衡浓度降低;Cr的浸出浓度与pH值的增高呈正相关;Cu和Zn具有两性浸出,形成U形曲线,在极端的酸性和碱性pH值时浓度升高。建筑垃圾再生骨料浸出后的重金属浓度低于我国相关标准,可作为路面填料。

Environmental Impact of Heavy Metal Leaching from Construction and Demolition Waste Aggregates

The pollution of construction and demolition waste (C & DW) to groundwater must be considered in exploring the applicability of C & DW aggregates as an alternative material for permeable pavement subbases. In this paper, two common C & DW recycled aggregates, namely, recycled brick aggregate (CB) and recycled concrete aggregate (RCA), were selected as research objects. The concentration of leached heavy metals and the release characteristics and rules of contaminants were examined, and the influences of factors such as mix ratio, liquid-solid ratio, pH value and others on the leached concentration of heavy metals were analyzed. Results demonstrated that in pure brick environment, the leached concentration of Cd, Cu, Ni, and Zn hit the lowest, while in pure concrete environment, the leached concentration of Cr and Pb minimized. As liquid-solid ratio varied, the leached concentration of Cd and Zn barely changed, implying that Cd and Zn reached equilibrium. With the rising of liquid-solid ratio, the leaching rate and volume of Cr and Pb both increased, whereas the leaching rate of Cu and Ni dropped. At different pH values, the trends of leached concentration of Cd, Ni, and Pb varying with time were similar in general: with the rising of pH value, the balanced concentration reduced. The leached concentration of Cr displayed a positive relation with pH value. The leached concentration of Cu and Zn surged at extreme pH values, presenting a U-shaped curve. In conclusion, C & DW recycled aggregates can be used as pavement filler as the concentration of heavy metals after leaching meets China's relevant specifications.