Graduation Semester and Year

2018

Language

English

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering

Department

Civil Engineering

First Advisor

Xinbao Yu

Abstract

Chemical stabilization of expansive soil has been practiced for quite a time now. The use of lime/cement stabilization as a traditional method has been well acknowledged, understood and standard guidelines for practice have been developed. However, owing to certain demerits like high production and application cost, environmental impact, durability issues and most importantly incompatibility with high-sulfate soil leading to excessive heaving and swell, there is need to develop alternatives to these stabilizers. Non-traditional stabilizers like ionic soil stabilizer have been used by manufacturers in the past and claimed to effectively reduce the swell-shrink behavior of expansive soil. Undocumented results, the absence of laboratory tests, proprietary issues, however, have forced engineers to be reluctant about its use and accept it as suitable options to existing stabilizers. This study has focused on meeting existing shortcomings of the ionic stabilizers by studying their effect on expansive soil both in the laboratory and field. For this purpose, an ionic soil stabilizer was selected from the available commercial products in the market. The stabilizer was used to treat the expansive soil from Carrollton, Texas. The stabilizer was also used to treat a site in Burleson, Texas. The laboratory study focused on observing the effect of treatment on swell potential and strength of the soil at different application rates (1:150 and 1:300, volume of chemical to volume of water ratio) and curing days and validating the results through micro analysis of the soil. The laboratory tests include basic soil physical property and mechanical property tests such as Atterberg Limits test, bar linear shrinkage test, hydrometer test, standard compaction test, 1-D swell, and unconfined compressive strength test. Soil minerology tests including cation exchange capacity and specific surface area were performed to deterine soil mineralogy behaviors. In addition micro tests such as Scanning Electron Microscope (SEM) imaging, energy dispersive spectrometer tests were perform to determine micro structure and elemental behavior of both treated and untreated soils. Further studies were conducted on the samples treated in the field as well. With Carrollton soil, it is found the standard compaction curve is altered for the treated soil. The optimum moisture content increases while the maximum dry density decreases. For treated soil compacted at the optimum moisture content and maximum dry density of the treated soil, more than 50% of swell reduction is observed and the UCS of the treated soil slighlty decreases. For Burleson soil, the standard compaction curve of the treated soil is similar to the one of untreated soil. The ionic soil stabilizer is found to successfully reduce the swelling potential and PVR of the active zone of expansive soil generally extending up to 10 feet in field treatment. In the field, the soil is usually wetted to near saturation with the liquid stabilizer. The application mass ratio which is the amount of stabilizer available for soil solids is relatively higher because of the treatment method used in the field. The tests in the laboratory were done at the moisture content near to optimum. In the light that improvements were observed with the Burleson soil, the stabilizer shows a potential in expansive soil stabilization. There are some discrepancies in findings from the lab and the field which can be ruled out in the future with the development of techniques to closely simulate the field condition. Ineffectiveness of stabilizer on Carrollton soil at given test conditions might be an indication that stabilizers work under certain specified conditions only and concludes that pre-study of the suitability of stabilizer is essential. Nevertheless, incorporating all the shortcomings in the current study, ionic stabilizers can have a good potential in the future for stabilization of expansive soil.

Keywords

Expansive soils, Stabilization, Ionic stabilizer

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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