STABILIZATION OF HIGHLY EXPANSIVE BENTONITE SOIL USING POLYPROPYLENE FIBER AND GROUND GRANULATED BLAST FURNACE SLAG

Author

Amit Neupane, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2022

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Kolay, Prabir

Abstract

The expansive nature of the soil has been a major problem in the engineering field, as its shrinking and swelling phenomenon damages the building structures, bridges, roads, etc., and provokes potential failures in the various infrastructure. Hence, a detailed investigation of the soil types and their properties before any construction is important. With the pre-knowledge of the soil types, different stabilization techniques can be applied in the field to reduce the swelling or shrinkage property of such soils. There are different methods to identify such properties of soil; among them, the Atterberg limit, consolidation test, and expansivity index test are the widely practiced methods. The present study investigates the use of polypropylene fiber, and ground granulated blast furnace slag (GGBS) mixed separately with highly expansive commercially available bentonite soil to reduce the expansivity index and other swelling & shrinkage parameters. The percentages of the fiber used were 0%, 0.25%, 0.5%, 0.75%, and 1.0% mixed with bentonite soil by dry weight. The proportions of GGBS were 0%, 5%, 10%, and 15% mixed with bentonite soil by dry weight. The index properties of the treated bentonite soil were tested by the Atterberg limit test, specific gravity test, and linear shrinkage test. The engineering properties were performed by compaction, expansivity index, and one-dimensional consolidation test. SEM, EDX, and electrokinetic tests were performed for microstructural analysis of the soil particle. Respective designated standards were followed for the various test. The result shows a significant reduction in the expansivity and swelling index of the bentonite soil while treated with either of the additives, i.e., fiber or GGBS. The reduction in the expansivity index of the soil mixed with fiber ranged from 29.04 to 47.41% at 0.25% to 1.0% of the fiber content. With the GGBS additive, the expansivity index reduced impressively from 75.9% to 80.49% at the 5% to 15% of GGBS content. Similarly, there is a substantial reduction in the swelling pressure, which ranges from 24.97% to 66.43% with the addition of 0.25% to 1.0% fiber and from 21.86% to 46.07% with the addition of 5% to 15% GGBS. This research is focused on the use of additives polypropylene fiber and GGBS as the best alternatives for stabilizing highly expansive bentonite soil. The study also ensures that the sustainability of the environment can be achieved by the practical application of industrial wastes like GGBS.