电镀行业污染土固化体无侧限抗压强度演化规律研究

电镀行业在生产过程中会对周边区域的土壤造成严重的重金属污染。以电镀行业重金属复合污染土壤为研究对象,选用水泥作为固化/稳定化胶凝材料对污染土进行固化稳定化处理,以污染土固化体的无侧限抗压强度(UCS)为目标,通过对固化材料配比的优化,在实验室中对不同养护龄期重金属污染土固化体的UCS进行了测试,并通过X射线衍射分析,探讨了重金属对固化体强度的影响及水泥对重金属的稳定化机理。结果表明：材料配比优化后的重金属污染土固化体在养护3天时的UCS即可满足EPA的推荐值；重金属离子会在养护初期(1天)对水泥的水化形成明显的阻滞作用,从而使固化体在养护初期的UCS显著降低；此外,重金属离子会使水泥的水化向次级反应进行,生成强度较低的钙钒石,并降低固化体在整个养护期内的UCS；水泥的水化反应对于重金属Pb的稳定化作用除了会使其转化氢氧化物的沉淀之外,还会使其转化为稳定的化合物。

Evolution rules of the unconfined compressive strength of soil contaminated by electroplating industry

The soil layers where located around the electroplating industry commonly contaminated by heavy metals. The soil which contaminated by composite heavy metals coming from electroplating industry were selected as the object. The ordinary Portland cement was chose as binder materials for solidification / stabilization. The Unconfined Compress Strength (UCS) of solidified matrix was selected as the final achievement. In order to consider the physical and chemical characteristics of the solidified matrix, the soil-binder ratio was optimized, and then the UCS and the X-ray diffraction of solidified matrixes with different curing time were tested for revealing the UCS of solidified matrix influenced by heavy metals contained in soil and the heavy mental solidification/stabilization mechanism. The results indicate that the compress strength of solidified matrix after 3 days curing time could achieve the EPA recommended value. The heavy metals contained in soil can retard the cement hydration reaction at early curing time (i.e. 1 day) which leading to the intensive decreasing of the UC. Besides, the heavy metals can change the cement hydration to the secondary reaction which forming the Ettringite with low strength during the whole curing time, which leading to the UCS of the solidified matrix decrease. The heavy metal element, Lead, could be stabilized both in hydroxide precipitation form and in stable chemical compound.