| Abstract: | Soil stabilization is often employed to enhance natural soils⁰́₉ geotechnical properties. Due to the environmental impacts of commonly used calcium-based stabilizers, eco-friendly and sustainable additives such as biopolymers, microbial activities, and Geopolymers have been receiving increased attention. While the improvement of strength and shrinkage behavior due to Geopolymers has been investigated, studies on stabilizing sulfate-rich expansive clayey soils and weak sandy soils using Geopolymers is limited. This work aimed to study the performance of Geopolymers in stabilizing the aforementioned soils in two phases (I and II). Phase I explored the interaction mechanisms among the soil, Geopolymer stabilizer and dosages, high and low sulfates in the clayey soil. Typically, alumina and sulfates in the soil react with calcium ions in stabilizers to form Ettringite and result in sulfate-induced heaving. The soils cured and treated with the stabilizers were subjected to laboratory tests including strengths, swelling-shrinkage strains, and resilient strains to analyze the effects of Geopolymer dosages and curing period on the stabilization of sulfate-rich soils. The results were compiled and compared with the same sulfate-rich soils treated with lime, which are regarded here as control soils. Test results showed the effectiveness of Geopolymer treatment in stabilizing sulfate soils. Phase II assessed the feasibility of using Geopolymers to stabilize weak sandy soils. This phase included designing and conducting experimental studies, analyzing the results, and assessing soil property improvements. Additionally, microstructural studies were performed on treated soils to evaluate the stabilization mechanisms in both soils. Overall, stabilization methods and their potential contributions to sustainable improvements for civil infrastructure works were addressed, including the implementation of them in flexible pavement designs. Sustainability evaluations were determined addressing environmental, cost, and societal impacts of Geopolymer and traditional treatments based on a laboratory-scale scenario. These results have presented them in a comprehensive and sustainable framework. Although this analysis identified some limitations of Geopolymer treatments, it indicated various approaches to enhance sustainability aspects in construction projects by using them in co-additive roles. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/197236 |
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