碳化作用下水泥固化/稳定化重金属污染土的性状演变及其评价

Heavy metal contaminated soil treated by cement-based solidification/stabilization subjected to reaction with carbon dioxide is referred to as carbonation. This process results in the change of performance of solidified/stabilized heavy metal contaminated soils, which buries potential danger of engineering disaster and environmental safety. In order to reveal the carbonation mechanisms of heavy mental contaminated soil treated by cement-based solidification/stabilization, a series of macroscopic and microcosmic tests on artificial and natural heavy mental contaminated soils treated by cement-based solidification/stabilization with and without carbonation will be conducted. The changes of physical, mechanical and chemical leaching characteristics of heavy mental contaminated soils treated by cement-based solidification/stabilization after carbonation will be analyzed. The microscopic structure parameters of the stabilized soil will be related to their physical and mechanical properties and chemical leaching. The coupling mechanism between the heavy metals leaching and the change of total porosity and pore size distribution will be revealed. At last, a new model will been constructed, which will depict the integral carbonation process of solidified/stabilized heavy metal contaminated soils, including of the mineral phase and its solubility changing, the interaction of leaching and porosity of soils, and the dynamic solute transport from the soils to the surrounding environment. It is expected that the results will provide theoretical basis for the carbonation prevention and control and optimum design of heavy metal contaminated soil treated by cement-based solidification/stabilization. Meanwhile, it is believed that the results will ensure the safety of the reuse of heavy metal contaminated sites improved by solidification/stabilization and promote the heavy metals contaminated soil treatment and remediation theory and level.

水泥固化/稳定化重金属污染土会受到长期的二氧化碳碳化作用，导致其服役性状的演化和变异，为工程灾变与环境安全埋下了隐患。为了揭示碳化作用下水泥固化/稳定化重金属污染土的性状演化规律及内在机制，定量评价碳化效应，本项目采用“室内加速模拟实验和理论分析相结合、宏观与微观相结合”的技术路线，系统研究碳化过程中水泥固化/稳定化重金属污染土微观结构特征、物理、力学和化学淋滤特性的演化规律，阐明固化土微观结构特征参数与其物理力学和化学浸出特性的内在关联，揭示固化土淋滤与孔隙变化的耦合机理，构建考虑碳化作用下固化/稳定化重金属污染土矿物成分物相演变与溶解、淋滤与孔隙变化耦合、溶质动态运移全过程的碳化效应定量评价模型。研究成果可为水泥固化/稳定化重金属污染土的碳化防控与评价、设计方法优化提供理论依据，确保重金属污染场地二次开发利用的安全性，提高我国重金属污染土的修复技术水平。

水泥固化稳定化重金属污染土会受到长期的二氧化碳碳化作用，导致其服役性状的演化与变异，为工程灾变与环境安全埋下了隐患。为了揭示碳化作用下水泥固化稳定化重金属污染土的性状演化规律及内在控制机制，本项目采用室内加速模拟试验与理论分析相结合、宏观与微观相结合的技术路线，着重研究以下关键内容：1）水泥固化土碳化深度的测试与评价，2）碳化作用下固化污染土微观结构、工程特性和化学溶出特征的演化规律，3）考虑碳化效应的固化污染土化学溶出评价方法。主要研究成果包括：1）通过室内加速碳化试验，基于Papadakis碳化模型和气体渗透模型，建立水泥固化土碳化深度预测模型，分析电阻率与碳化深度的关系，提出基于电阻率测试的碳化深度评价方法；2）通过微观结构测试，分析碳化作用对水泥反应产物、重金属矿物形式、微观矿物形态和微观孔隙结构的影响规律，明确碳化过程中CaCO3、CSH和CH的质量分布，揭示碳化作用下固化土微观结构演化的机理；3）通过强度测试和渗透试验，分析碳化作用对水泥固化土的无侧限抗压强度、应力应变特性和渗透特性的影响规律，建立强度和渗透系数与微观孔隙结构的关系，探讨碳化作用下水泥固化重金属污染黏性土强度特性变化的内在控制机理；4）通过pH相关溶出试验、连续提取试验和半动态淋滤试验，研究碳化作用对污染物溶解度、污染物化学赋存形态和污染物运移特性的影响规律，揭示碳化作用下污染物溶解度与pH的关系，探讨污染物的溶出机理，研究成果可用于评价水泥固化重金属污染黏性土中污染物的长期溶出潜能；5）提出考虑碳化效应的固化污染物土化学溶出评价框架，基于评价框架和水泥固化土碳化深度预测模型，给出溶质平衡控制情况下和溶质运移控制情况下，考虑碳化效应的污染物长期溶出计算方法。研究成果可为水泥固化稳定化重金属污染土的碳化防治与评价、设计方法优化提供理论依据，确保重金属污染场地二次开发利用的安全性，提高我国重金属污染土的修复技术水平。