温度对重金属污染土固化稳定长期性能影响机理与控制研究

Stabilization/Solidification has emerged as a cost effective and efficient method for the implementation of a range of remediation treatments. A comprehensive laboratory tests and theoretical analysis of MgO-based binders (MgO, GGBS and CaO) stabilised/solidified heavy metal contaminated clays are used in this project, to study the effects of temperature on novel binders stabilized/solidified heavy metal contaminated clays and its control methods. The key problems to be addressed are to: 1, study the effects of temperature on the binding mechanism of these stabilized/solidified samples, through the analysis of their physico-chemical performance and microstructures; 2, reveal the effects of temperature on the long-term durability of these stabilized/solidified samples, by testing their wet-dry and thaw-freeze cycling; 3, analyze the relationship between the temperature effect, the leaching properties and diffusion coefficient of these solidified soils under semi-dynamic leaching tests and empirical formulas; and 4, explore the influence of temperature on the ecological pollution risk of stabilized/solidified samples based on the ecological risk index and risk assessment methods. The results will expand the application of stabilization/solidification technology, and provide important scientific guidance and theoretical support for improving the utilization rate of contaminated soils as well as realizing the sustainable development in China.

固化稳定化技术因低成本，高效率等优势，被广泛应用于污染场地的再开发利用中。本项目以氧化镁（MgO），矿渣（GGBS）和煅烧白云石（CaO）材料组成的新型固化剂处理的复合重金属污染粘土为研究对象，采用室内试验与理论分析相结合的技术路线，系统研究温度对新型固化剂固化稳定化重金属污染黏土长期稳定性的影响规律与控制方法。拟解决以下关键问题：1、通过物化性质、微观结构等，研究温度效应对该固化污染土作用机理的影响规律；2、通过干湿和冻融循环等试验，明确温度对新型固化剂固化稳定化重金属污染黏土耐久性的影响规律；3、通过半动态溶出试验和经验公式求算，归纳分析温度效应与新型固化污染土的溶出量、扩散系数等之间的关系；4、利用生态危害指数和风险评估方法，探索温度对新型固化污染粘土对生态污染风险的影响规律。研究成果有益于拓展固化稳定化技术的应用范围，对提高土体利用率，实现可持续发展提供重要的科学依据和理论支撑。

我国地域辽阔，气候条件复杂，土体温度季节变化幅度大，温度对土壤的物理化学、力学方面影响显著，但目前温度效应对固化污染土的研究鲜有涉及。本项目以氧化镁（MgO），矿渣（GGBS）和煅烧白云石（CaO）组成的新型固化剂处理的复合重金属污染粘土为研究对象，通过无侧限抗压强度试验、毒性浸出试验、冻融循环试验、干湿循环试验半动态溶出和微观试验等，研究了不同养护温度对GMC固化重金属污染土强度特性、环境安全性、耐久性及其微观机理的影响，并与水泥（PC）固化现场复合污染土的处理效果进行了对比研究，得出以下结论：1、随着养护温度的提高，GMC固化土的无侧限抗压强度提高，且GMC固化土强度受养护温度的影响程度高于PC固化土；2、随着固化剂掺量和养护温度的提高，GMC与PC固化土的铅锌浸出量下降，且GMC固化铅锌污染土的浸出量受养护温度的影响更大；两种固化土的铅锌浸出量均随污染土中Pb浓度的增加而提高，与PC相比，GMC固化剂处理高浓度Pb污染土和复合污染土效果更好；3、GMC与PC固化土的抵抗冻融循环与干湿循环的能力均随养护温度的提高而增强；4、GMC固化土的水化产物主要为水化硅酸钙（C-S-H）和水滑石（Ht），扫描电镜结果显示，高温养护下，GMC固化污染土网状结构增多，水化过程加速，Ht的发育程度更完整，结构更致密。