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Effectiveness of polymer for mitigation of expansive soils




Taher, Zana, author
Scalia, Joseph, IV, advisor
Bareither, Christopher A., advisor
Valdes-Vasquez, Rodolfo, committee member

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The objective of this study was to determine the effectiveness of commercially available polymer treatment as a mitigation technique for expansive soils in transportation applications. Four commercially available polymers were used in this research. A survey of state departments of transportation within the mountain-plains region (Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming) was conducted to define the state-of-the-practice in expansive soil mitigation. A literature review on expansive soil treatments, with a focus on polymer mitigation, was also performed to establish the state-of-the-art in expansive soil mitigation. The soil tested was composed of expansive soil from Fort Collins, Colorado, that classified as low swelling, amended with 15% (high swelling) sodium bentonite. Fifteen percent bentonite was selected to meet the Federal Highway Administration (FHWA) classification for highly expansive soil. Treated and untreated soils were classified, and tested for swelling, strength, and hydraulic conductivity. Four commercially available polymers were tested; lime and fly ash, two common techniques used in treatment of expansive soils, were tested for comparison. Preliminary swell tests were performed on four commercially available polymers, P1, P2, P3, and P4, to analyze the relative effectiveness of the polymers. P4 was selected for this study based on the high effectiveness of P4 from the swell test results. P4 reduced expansive soil swelling and increased strength, but was less effective than lime or fly ash. Based on reduced swelling, and increased strength, lime was the most effective treatment for stabilizing and strengthening the expansive soil tested. Swell test data do not support use of P4 (or P1, P2, P3) over traditional treatments for swell mitigation of the expansive soil tested in this study. However, lime and fly ash treatments resulted in multiple orders-of-magnitude increases in hydraulic conductivity, while P4 did not. Since water ingress is required for soil swelling, future testing that couples the effects of hydraulic conductivity and swelling is recommended. In addition, testing of other commercially available polymers, and additional soils (such as sulfate rich soils) is recommended.


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