STABILIZATION OF BENTONITE CLAY USING RECYCLED GLASS POWDER AND POLYPROPYLENE FIBER

Author

Bibek Karki, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2023

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Kolay, Prabir

Abstract

Expansive soils undergo significant volume changes with the fluctuations in moisture content expand with increased moisture and shrink with drying. This behavior of expansive soil brings challenges for civil engineering projects. Infrastructures such as residential foundations, transportation networks, utilities, retaining structures, etc. face considerable risk when constructed over expansive soils. Despite the challenges brought by expansive soils, construction on them in many circumstances is unavoidable and economically unviable to replace entirely. Soil stabilization, therefore, is one of the best alternatives for improving expansive soil before any construction. The present study uses two sustainable materials: recycled glass powder (RGP) and polypropylene fiber (PPF) in stabilizing highly expansive bentonite clay (BT). The study focuses on evaluating the expansive and swelling properties of the treated and untreated bentonite clay by performing various tests such as Atterberg limits, free swelling index, expansivity index, and one-dimensional consolidation test among others. Recycled glass powder was incorporated in the percentages of 5%, 10%, 20%, and 30% by dry weight with the bentonite clay (BT), while polypropylene fiber was introduced in the percentages of 0.25%, 0.5%, and 1.0% by dry weight with the base mix of 20% glass powder treated bentonite clay (BT + 20% RGP). The results demonstrated a decrease in linear shrinkage with an increase in both glass powder and fiber content. The free swell index (FSI) decreased considerably up to 62.23% with the addition of glass powder in increasing percentages. A significant reduction of 50.29% was observed with the Expansive Index (EI) when treated with 30% glass powder. By introducing fiber, the maximum reduction in Expansive Index (EI) of 31.78% was observed with 0.5% fiber content. The compression and swelling index values decreased with the addition of glass powder. The optimum mix for reducing the swelling and compression index was found to be at 20% RGP content. The swelling index was reduced by 37.05% at 20% RGP content, while further adding the recycled glass powder increased the swelling index value. On the contrary, the intrusion of polypropylene fiber did not show any definite trend, and the index values mostly increased. Overall, recycled glass powder (RGP) and polypropylene fiber (PPF) as stabilizing additives hold strong potential for improving the expansive and swelling properties of highly expansive bentonite clay.