Akula Pavan, Little Dallas N
Research Assistant, Texas A&M University.
Regents Professor, Texas A&M University.
MethodsX. 2020 May 28;7:100928. doi: 10.1016/j.mex.2020.100928. eCollection 2020.
Shrink-swell soils are predominant in various parts of the parts of the world. Lime has been extensively used to reduce the shrink-swell mechanism as it chemically reacts with soil minerals forming pozzolanic products such as calcite and calcium-silicate-hydrate (C-S-H). Conventionally, whether chemical treatment of soils results in effective pozzolanic stabilization reactions is determined anecdotally through engineering tests including unconfined compressive strength, plasticity index (PI), and pH tests. This study builds on existing literature regarding how more direct quantification of pozzolanic products can be obtained through tests that directly identify and quantify pozzolanic products, specifically in lime-treated clay soils. Specifically, x-ray diffraction (XRD) and differential thermogravimetric analysis (DTA) are used for this testing. Expansive soils with plasticity indices above 25% were selected for this study. Engineering tests on these lime-treated soils indicated significant improvement in strength and reduction in PI. In XRD analysis, pozzolanic products are assessed by the location and intensity of x-ray peak(s). The XRD data show a decrease in the intensity of alumio-silicate minerals such as kaolinite and smectite; silica and alumina are dissolved at a high pH and converted to pozzolanic products such as calcium-silicate-hydrate (C-S-H). DTA indicates the presence of C-S-H with the characteristic weight loss from 140°C to 250°C.The methodology describes the following: ● Sample preparation steps for XRD and DTA analysis. ● Analysis of XRD results and DTA analysis.
胀缩性土壤在世界各地区都很常见。石灰已被广泛用于减少胀缩机制，因为它与土壤矿物发生化学反应，形成火山灰产物，如方解石和硅酸钙水合物（C-S-H）。传统上，土壤的化学处理是否会导致有效的火山灰稳定反应是通过包括无侧限抗压强度、塑性指数（PI）和pH测试在内的工程试验来经验性确定的。本研究基于现有文献，探讨如何通过直接识别和量化火山灰产物的测试，特别是在石灰处理的粘土中，更直接地量化火山灰产物。具体而言，本测试使用了X射线衍射（XRD）和差示热重分析（DTA）。本研究选择了塑性指数高于25%的膨胀土。对这些石灰处理土壤的工程试验表明，强度有显著提高，PI降低。在XRD分析中，通过X射线峰的位置和强度来评估火山灰产物。XRD数据显示，高岭石和蒙脱石等铝硅酸盐矿物的强度降低；二氧化硅和氧化铝在高pH值下溶解，并转化为火山灰产物，如硅酸钙水合物（C-S-H）。DTA表明存在C-S-H，其特征失重温度为140°C至250°C。该方法描述了以下内容：● XRD和DTA分析的样品制备步骤。● XRD结果分析和DTA分析。
