Abstract
Expansive clay soils are the types of soils whose volume changes with the change in water content. They have a behavior of swelling and shrinking that is a serious hazard to structures built over them. Expansive soils are abundantly existing soil types in Ethiopia, particularly Addis Ababa. This paper shows the outcomes of an attempt to reinforce and stabilize expansive clay soil with plastic bottle strips. The plastic strips were prepared and added at three different mixing ratios (0.5%, 1% and 2%) by weight and in three different aspect ratios (5 mm × 7.5 mm, 10 mm × 15 mm, 15 mm × 20 mm). The experimental results showed that there was a significant improvement in shear strength parameters. The swelling and desiccation cracking behavior of the soil were also expressively reduced. There was a substantial reduction in the optimum moisture content and slight increment in maximum dry density. The optimum plastic size (aspect ratio) and plastic content that results in optimum result can be selected based on the importance of the selection parameter for a specified engineering work. Stabilizing expansive clay soils with waste plastic bottles simultaneously solves the challenges of improper plastic waste recycling that is currently a teething problem in most developing countries. The results obtained from this study favorably suggest that inclusion of this material in expansive soils would be effective for ground improvement in geotechnical engineering.
Highlights
The optimum plastic size and plastic content that results in optimum result can be selected based on the importance of the selection parameter for a specified engineering work
Standard Proctor Compaction Test Results One of the ways the effect of adding plastic into the soil was checked was in terms of the soil’s improvement during compaction. This improvement was expressed in the change in the maximum dry density (MDD) and optimum moisture content (OMC)
Increase in plastic size for the same percentage has resulted in an increase in soaked California Bearing Ratio (CBR) value but increase in plastic content for the same plastic size increases the soaked CBR decreases
Summary
They expand when exposed to excess water and shrink in hot weather conditions where there is scarce amount of water. They can be identified in the field in dry seasons as they show deep cracks of polygonal patterns. This behavior of swelling and shrinking of expansive clay soils in turn affects the stability of structures that is built over these soils causing a serious hazard. In order to build on expansive soils, they need to be stabilized to reduce their swelling and improve their mechanical capacities
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