Enhancement of Muscat’s Expansive Soil Using Waste Gypsum

Abstract

Expansive soils are known to show significant volumetric changes in response to changes in the moisture content. Such soils swell when the moisture content is increased and shrink when the moisture content is decreased, thereby causing distress and damages to structures founded on them. Construction developments on naturally occurring expansive soils are usually problematic. This study examines the properties of expansive soil obtained from the city of Muscat in Oman. The expansive soil samples were further treated with gypsum, which was obtained from waste plasterboards, at varying quantities of 3%, 6%, 9% and 12% by mass in an attempt to stabilize the soil. Based on USCS classification system, the expansive soil was identified a poorly clay with high plasticity (CH) with AASHTO classification of A-6. The pH test confirms the reaction between expansive and gypsum, while both the compaction and unconfined compression strength (UCS) tests revealed the optimum percentage of gypsum required to enhance the properties of expansive soil to be 9% by mass. The unconfined compression strength (UCS) test yielded a 37.7% increase over that of untreated expansive soil at 28 days of curing. The California Bearing Ratio (CBR) test of the treated soil yielded a 57% increase in CBR value for expansive soil treated with 9% of waste gypsum over untreated expansive at the unsoaked state and 70% at soaked state. Overall, a solid understanding of the physical and engineering properties of expansive soil, and the confirmation of the potential use of gypsum for its stabilization, was achieved in this study.