Lime stabilization is a common technique used to improve the engineering properties of clayey soils. The process of lime stabilization can be split into two parts. First, the mobilization and crowding of $\mathrm{C}{\mathrm{a}}^{2+}$ ions or $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$molecules from hydrated lime at net negative surface charge sites on expansive clay colloids. Second, the formation of pozzolanic products including calcium-silicate-hydrate (C-S-H) because of reactions within lime-soil mixtures. The pozzolanic reaction is generally considered to be more durable, while the $\mathrm{calcium}$ adsorption has been associated with more easily reversible consistency changes. This study offers a protocol to assess whether the stabilization process is dominated by durable C-S-H (pozzolanic) reactions or a combination of cation exchange and pozzolanic reactions. Expansive clays with plasticity indices >45% from a major highway project in Texas are the focus of lime treatment in this study. The protocol consists of subjecting lime-soil mixtures to a reasonable curing period followed by a rigorous but realistic durability test and investigating the quality and quantity of the pozzolanic reaction product. Mineralogical analyses using quantitative X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicates the formation of different forms of C-S-H. In addition, geochemical modeling is used to simulate the lime-soil reactions and evaluate the effect of pH on the stability of C-S-H. The results indicate C-S-H with Ca/Si ratio of 0.66 as most the stable form of C-S-H among other forms with Ca/Si ratio ranging from 0.66 to 2.25. The effect of reducing equilibrium pH on C-S-H is also evaluated. A reduction in pH favored dissolution of all forms of C-S-H indicating the need to maintain a pH ≥ 10.

石灰稳定化是用于改善粘土质工程特性的常用技术。石灰稳定过程可以分为两部分。一是动员和拥挤$\mathrm{C}{\mathrm{一种}}^{\mathrm{2个}+}$ 离子或 $\mathrm{钙}{（\mathrm{哦}）}_{\mathrm{2个}}$膨胀粘土胶体上净负表面电荷部位的熟石灰中的分子。第二，由于石灰-土壤混合物中的反应，形成了包括硅酸钙-水合物（CSH）的火山灰产物。通常认为火山灰反应更持久，而$\mathrm{钙}$吸附与更容易逆转的稠度变化有关。这项研究提供了一个协议，以评估稳定过程是由持久的CSH（火山灰）反应还是阳离子交换和火山灰反应的组合所主导。这项研究的重点是来自德克萨斯州某大型公路项目的可塑性指数> 45％的膨胀粘土。该方案包括对石灰-土壤混合物进行合理的固化，然后进行严格但切合实际的耐久性测试，并调查火山灰反应产物的质量和数量。使用定量X射线衍射（XRD）和热重分析（TGA）的矿物学分析表明形成了不同形式的CSH。此外，地球化学模型用于模拟石灰-土壤反应并评估pH对CSH稳定性的影响。结果表明，Ca / Si比为0.66的CSH是CSH的最稳定形式，而Ca / Si比为0.66至2.25的其他形式。还评估了降低平衡pH对CSH的影响。pH值降低有利于所有形式的CSH溶解，表明需要保持pH值≥10。