水泥固化锌污染红粘土强度与微观孔隙特征

污染场地开挖置换后的污染土经过固化处理（S/S法），可作为浅层地基或护岸等非敏感区域的建筑材料，进行污染土的二次利用。针对该项技术，将一定量硝酸锌溶液与风干后红粘土混合，掺入适量水泥，并搅拌均匀、压实成型，标准养护7 d和28 d后依次进行无侧限抗压实验、压汞实验和含水率、体积等指标的测定，研究不同锌离子浓度、水泥掺量和养护龄期对锌污染红粘土水泥固化产物强度、微观孔隙和含水率等的影响。实验结果表明：水泥掺量在10%以内，锌离子浓度小于5000 mg·kg-1，固化物强度随龄期增长而增加；锌离子浓度大于5000 mg·kg-1，强度随龄期增长而先增加后减小。水泥掺量6%和8%时，固化物强度与锌离子浓度呈负相关；而水泥掺量10%时，锌离子浓度对强度的影响存在阈值，且阈值在1000 mg·kg-1附近。与不含锌离子的28 d固化物相比，锌离子浓度小于1000 mg·kg-1时，固化产物孔径小于10 nm的孔隙增加，孔径大于10μm的孔隙减少，强度提高；锌离子浓度在大于1000 mg·kg-1时，严重阻碍C-S-H凝胶物的生成，10μm以上的孔隙和总孔隙率均显著增加，并且生成大量孔径为0.1~10μm的无定型物，同时使红粘土出现亲水性，养护过程中吸收水分且体积增加，强度则大幅度降低。

Strength and micropore characteristics of cement-solidified/stabilized zinc-contaminated red clay

Contaminated soil excavated from contaminated sites may be used as building materials for shallow foundation or bank protection or other insensitive areas after solidification/stabilization(S/S)with cement, enabling reutilization of contaminated soil. In this study, air-dried red clay sample amended with zinc nitrate was stirred with cement and was then compressed into specimens. The specimens were cured for 7 d or 28 d under standard conditions. The effects of different zinc concentrations, cement rates, and curing times on the strength, micropore, and moisture content of cement-stabilized zinc-contaminated red clay product were examined by unconfined compression test, mercury injection experiment, moisture content measurement, and volume measurement. Results showed that the strength increased with the curing time if cement rates were less than 10%and zinc ion concentrations below 5000 mg·kg-1. However, the strength initially increased but then dropped with curing time if zinc concentrations was above 5000 mg·kg-1. At cement rates of 6%and 8%, the strength of the ce-mented products was negatively correlated with the zinc ion concentration. At 10%of cement rate, there was a 1000 mg·kg-1 threshold of zinc ion concentration that influenced the strength. Compared with zinc ion-free 28 d solidified/stabilized product, the products with zinc concentrations below 1000 mg·kg-1 had more pores smaller than 10 nm, fewer pores larger than 10μm, and greater strength. At zinc con-centrations higher than 1000 mg·kg-1, less C-S-H gel was produced, more pores larger than 10μm were found, greater total porosity ob-served, and more amorphous substances with 0.1~10μm pore size detected. High Zn additions increased hydrophilicity of the red clay, re-sulting in elevated water absorption during curing, and thus dropped strength.