Soil stabilization with gypsum: A review

Abstract

The demand for sustainable ground improvement methods is rising as urban development expands into areas with challenging soil conditions. Traditional approaches, mostly reliant on cement and lime, contribute significantly to anthropogenic greenhouse gas emissions. Researchers, therefore, are constantly searching for new environmentally friendly stabilization methods to improve the engineering properties of soils. One alternative material used for this purpose is gypsum in its hydrated and dehydrated (hemihydrate/anhydrate) states. Not only can natural gypsum be used for ground improvement but also industrial waste and by-products (e.g. used or waste plasterboard, phosphogypsum, flue gas desulfurization gypsum, titanium dioxide production gypsum by-product) can be recycled, and used. Successful application of these materials could lower the carbon footprint of the construction industries (by reducing the consumption of cement and lime) as well as other industries (by recycling their waste and by-products). However, using gypsum presents challenges due to its moderate water solubility, the formation of swelling clay minerals under certain conditions, and the tendency of dehydrated gypsum to swell upon exposure to water, to name a few. Furthermore, the mechanisms leading to the improved behavior of the gypsum-treated soils are complicated, which has resulted in some seemingly contradictory results reported in the literature. This study presents a systematic and extensive review of the observed behavior of gypsum-treated soils and the different mechanisms causing the observed behavior. The research gaps and the required future steps to address these gaps have been identified and reported. A summary of the effect of gypsum treatment on the mechanical and engineering properties of soils, including unconfined compressive strength (UCS), California Bearing Ratio (CBR), swell potential, Atterberg limits, optimum moisture content (OMC), maximum dry density (MDD), durability, and environmental effects has also been presented.

Keywords

• Ground improvement
• Soil stabilization
• Gypsum
• Cementitious hydration products
• Ettringite
• Soil strength