A Bottom-up Approach to Design of Chemical Soil Stabilization Using Thermodynamic Modeling

粘土存在于美国的大部分地区，如德克萨斯州、俄克拉荷马州、堪萨斯州和其他地方。由于粘土不适合作为公路和其他结构建筑的基础，因此采用各种稳定技术来改善其性能。使用石灰和波特兰水泥的化学土壤稳定是应用最广泛的方法之一。通常，土壤稳定设计需要进行实验室规模的可处理性研究，以确定最佳化学剂量，并且预测稳定土壤数月或数年的长期行为的能力仍然有限。目前还缺乏描述稳定粘土中随时间变化的化学反应的模型，这对于提高我们的预测能力是必要的。因此，该项目的总体目标是生成基本的动力学和热力学模型，以定量描述粘土矿物和常用稳定剂（石灰、波特兰水泥）之间化学反应的演变。该项目的长期目标是利用这些模型来预测稳定粘土的长期行为，并为混合设计提供信息，从而最大限度地减少进行可处理性研究的需要。此外，这些模型将成为评估不同情景下化学稳定土壤行为的工具（例如，增加碳酸化或酸化的影响）。将对八种不同的组合（不同粒径的纯高岭土、纯钠膨润土和一种用生石灰和波特兰水泥稳定的土壤）进行模型开发，这将提供a)纯矿物的基本数据；b)深入了解在实际土壤中的适用性。三种不同的技术（定量x射线衍射，热重和差热分析和核磁共振）将利用先进的光谱反褶积技术，随着时间的推移监测纯和反应系统中的固相组成。生成的数据将用于拟合每种粘土矿物的火山灰反应的动力学模型。此外，对孔隙溶液组成的监测将允许进行正反热力学建模，以预测系统的稳定性和潜在的演化。由于该项目的多学科性质，一个平行的目标是提供综合岩土工程，地球化学和材料科学的培训机会。专门设计的具有项目相关多学科概念的模块将被设计并整合到康涅狄格大学定期提供的教学和推广活动中，为广泛的学生受众提供一个可持续的平台，并扩展现有的计划，从K-4土壤模块到ASCE专业人士网络研讨会，新的本科课程和远程学习工程硕士。三个专业学会（化学、环境和土木工程）的参与将导致项目成果的相互促进和广泛传播。

Clay soils are present in large parts of the United States, such as Texas, Oklahoma, Kansas and others. Since clay soils are unsuitable as foundations for construction of highways and other structures, various stabilization techniques are employed to improve their properties. Chemical soil stabilization using lime and Portland cement is among the most widely applied approaches. Typically, design of soil stabilization requires the performance of lab scale treatability studies in order to determine the optimal chemical dosage, and there is still limited ability to predict the long-term behavior of stabilized soils over months and years. Models that describe the chemical reactions within stabilized clays over time are currently lacking and are necessary to improve our predictive ability. Accordingly, the overarching goal of this project is to generate the fundamental kinetic and thermodynamic models that will quantitatively describe the evolution of the chemical reactions between clay minerals and common stabilizers (lime, Portland cement). The long-term vision of the project is to utilize the models to predict long term behavior of stabilized clays and inform the mix design, minimizing the need to conduct treatability studies. In addition, the models will be tools for assessing the behavior of chemically stabilized soils under different scenarios (e.g. increased carbonation or impact of acidification).Model development will be done for eight different combinations (pure kaolinite with different particle sizes, pure Na-bentonite and one soil stabilized with quicklime and Portland cement) that will be provide a) fundamental data for pure minerals; and b) insight into the applicability on a real soil. Three different techniques (quantitative X-ray Diffraction, thermogravimetric and differential thermal analysis and Nuclear Magnetic Resonance) will be employed to monitor the solid phase composition in pure and reactive systems over time, utilizing advanced spectra deconvolution techniques. The generated data will be used to fit kinetic models for the pozzolanic reactions of each clay mineral. In addition, monitoring of pore solution composition will allow to conduct both forward and inverse thermodynamic modeling to predict the system stability and potential evolution. Due to the multi-disciplinary nature of the project, a parallel goal is to provide training opportunities integrating geotechnical engineering, geochemistry and materials science. Specifically designed modules with project-related multi-disciplinary concepts will be designed and integrated in regularly offered teaching and outreach activities at UCONN, providing a sustainable platform for continuous exposure of wide student audiences and expanding existing initiatives, from K-4 soil modules, to an ASCE webinar for professionals, new undergraduate courses and a distance learning Masters of Engineering. Engagement across three professional societies (chemistry, environmental and civil engineering) will result in cross-fertilization and wide dissemination of project results.