ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
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- Creators: Kavazanjian, Edward
Description
This document presents the assessment of the swelling behavior of expansive clay stabilized with bio-based silica gel and subjected to wetting and drying cycles. The expansive clay used in this research was obtained from Anthem, Arizona. Rice husk is a rich silica by-product of rice production with commercial uses and applications in the industry. Rice husk ash from two different sources -California (named ASU) and India- were subjected to chemical characterization. Fourier Transform Infra-red Spectroscopy was used to verify the functional groups of the gel formed. Results showed differences between the ashes from different sources and confirmed the presence of silica structure bonds. X-Ray Diffraction (XRF) results showed that the ASU ash contained more amorphous silica than the Indian ash.One dimensional swell and consolidation tests were performed to investigate the volume change behavior of the untreated and silica gel treated remoulded samples. The free swell of the clay decreased from 12.3% (untreated sample) to 7.2% (ASU sample) and 11.4% (Indian sample). The effect of the wet and dry cycles on the swelling and consolidation characteristics of the untreated clay demonstrated that the treatment is irreversible after three cycles. Swelling of clay treated with ASU ash was reduced after the first cycle, while that of the clay treated with Indian ash was reduced after three cycles. This was due to the gelation time difference between treatments. Scanning Electron Microscopy images showed that the structure of the untreated clay was discontinuous, flaky and without aggregations whereas particles in the treated samples were aggregated and new bonds were created, decreasing the surface area. The X-Ray Diffraction (XRF) results showed that the main mineral responsible for expansive behavior of the clay studied was illite. The d-spacing of the illite decreased from 4.47Å for the untreated clay to 3.33Å for the treated clay. This study demonstrates a promising technique for clay swelling reduction and a more sustainable solution than that available to current practicing engineering.
ContributorsBogere, Limon (Author) / Zapata, Claudia E (Thesis advisor) / Kavazanjian, Edward (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2020
Description
Expansive soils pose considerable geotechnical and structural challenges all over the world. Many cities, towns, transport systems, and structures are built on expansive soils. This study evaluates stabilization of expansive soils using silicate solution extracted from rice husk taking advantage of an agricultural material waste. Rice husk ash production was optimized considering several factors including rinsing solution, rinsing temperature, burning time, and burning temperature. Results indicated that washing the rice husk with HCl (1M) produced an ash with surface area of 320 m2/g and 97% of silicon oxide. Two local soils were treated with sodium silicate solution, silica gel at pH 1.5, and silica gel at pH 4 to evaluate its mechanical properties at curing times of 1 day, 7 days, and 14 days. Results indicated that sodium silicate solution reduced the one-dimensional swell by 48% for Soil A, however, swell for soil B remained about the same. Silica gel at pH 1.5 reduced the one-dimensional swell by 67% for soil A and by 35% for soil B. Silica gel at pH 4 did also reduce the free swell by 40% for soil A and by 35% for soil B. Results also indicated that the swell pressures for all treated soils increased significantly compared to untreated soils. Soils treated with sodium silicate solution showed irregular compaction curves. Silica gel-treated soils showed a reduction in the maximum dry unit weight for both soils but optimum water content decreased for soil A and increased for soil B. Atterberg limits were also reduced for sodium silicate and silica gels-treated soils. Swelling index for bentonite showed a reduction by 53% for all treated bentonites. Soil-water characteristics curves (SWCC) for sodium silicate-treated soils remined almost the same as untreated soils. However, silica gels-treated soils retain more water. Surface area (SSA) decreased for sodium silicate-treated soil but increased for all silica gels-treated soils. It was concluded that curing times did not show additional improvement in most of the experiments, but the results remained about the same as 1-day treatment. The study demonstrated that silicate solution is promising and sustainable technique for stabilization of expansive soils.
Contributorsalharbi, hani (Author) / Zapata, Claudia (Thesis advisor) / Kavazanjian, Edward (Committee member) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2020
Description
Microbially- and enzyme-induced carbonate precipitation (EICP and MICP) offer potentially sustainable and cost-effective mitigation methods for fugitive dust by forming an erosion-resistant crust on the soil through precipitation of a natural calcium carbonate (CaCO3) cement. While there have been isolated studies on the efficacy of the carbonate precipitation process, there are few systematic studies of the influence of the properties of the soil being treated (e.g., gradation, salt content) on the precipitation and the resulting wind erosion resistance. Moreover, the influence of environmental conditions on the durability of the crust formed by the induced carbonate precipitation has not been systematically investigated. In this research program, the efficacy and durability of EICP and MICP for dust mitigation were investigated for a variety of soil types and in different environmental conditions. Soil samples from seven sites with fugitive dust problems were treated with MICP or EICP and subjected to lab or field testing. The results of these tests showed that the effectiveness of biocementation treatment varies depending on the grain size distribution of soil and mineralogical composition. Testing on iron ore tailings materials demonstrated that treating by application of EICP solutions at lower concentrations (i.e., 0.5M and 0.75M of urea and calcium chloride) yielded effective results for poorly graded fine sand-sized tailings but the same solutions were ineffective for the well graded sand-sized tailings that contained large gravel-sized particles. Additionally, the application of MICP and EICP on sediments adjacent to a shrinking lake (the Salton Sea) with different salt contents exhibited enhanced performance in soils with lower salt content. The effect of temperature during deployment and precipitation cycles are shown to be significant environmental factors by simulating wetting-drying and freeze-thaw cycles in the laboratory. A dust-resistance crust formed through biocementation remained mostly intact after undergoing multiple cycles of wetting-drying. However, the durability of a dust-resistance crust formed through biocementation to multiple cycles of freeze-thaw depended on treatment solution concentration and soil grain size. Additionally, high temperature during field deployment of MICP adversely effected crust formation due to rapid evaporation that inhibited the complete hydrolysis of urea and the precipitation of carbonate.
ContributorsEhsasi, Farideh (Author) / Kavazanjian, Edward (Thesis advisor) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2023