地聚合物修复Pb污染土的浸出、强度与微观结构研究

Study on leaching,strength and microstructure for remediation of Pb contaminated soil by geopolymer

为解决硅酸盐水泥修复Pb污染土带来的高能耗、高污染及长效性不佳等问题,研制了新型地聚合物(GCS),并对某工业场地Pb污染土进行了治理,与相同条件下的硅酸盐水泥(OPC)进行了对比,研究了不同药剂掺量修复污染土的强度、溶出和微观结构等的变化规律,结果表明:GCS对Pb污染土治理效果远好于OPC;当药剂掺量为12%时,GCS修复土的强度、酸雨溶出浓度分别达到我国建筑填料强度限值(2.5 MPa)、地表水Ⅲ类标准(0.05 mg/L);修复机制和微观结构的不同是OPC、GCS修复土工程性能不同的内在原因,GCS的生成物质以C-A-S-H、N-A-S-H为主,而OPC的生成物质以AFt、C-S-H为主,由于C-A-S-H、N-A-S-H的胶凝、黏聚作用、Pb钝化能力都要强于AFt、C-S-H,从而使得GCS修复土的工程性能优于OPC修复土。

In order to solve such problems as the high energy consumption,heavy contamination and poor validity in remediation of Pb contaminated soils using ordinary portland cement(OPC),a novel geopolymer composed of cement and concrete and composites(CCS) was prepared to deal with Pb contaminated soils at a production site of which the performance was compared with the ordinary portland cement(OPC) under the same conditions.The effect of the dosage of reagents on engineering properties such as strength,leaching rate and microstructure of remediated soil was studied.Results show that the engineering properties of soil remediated with CCS were much better than that of OPC.The soil strength,acid rain leaching concentration of soil treated with CCS at a dosage of 12% accorded with the threshold value of strength(2.5 MPa) for building filler and standard of grade Ⅲ(0.05 mg/L) for surface water respectively.The difference of remediation mechanism and microstructure between CCS and OPC resulted in the diffe-rence of the engineering properties of soils treated.The hydration products from OPC was dominated by AFt,C-S-H but that of CCS was dominated by C-A-S-H,N-A-S-H.As the gelling,adhering and deactivating performance of C-A-S-H,N-A-S-H are higher than AFt,C-S-H,the engineering properties of soil treated with CCS were more favorable than OPC.