Stabilization of clayey soils with Tunisian phosphogypsum: effect on geotechnical properties
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ORIGINAL PAPER
Stabilization of clayey soils with Tunisian phosphogypsum: effect on geotechnical properties Hajer Farroukh 1,2 & T. Mnif 1 & F. Kamoun 1 & L. Kamoun 3 & F. Bennour 3 Received: 7 February 2018 / Accepted: 23 November 2018 # Saudi Society for Geosciences 2018
Abstract Phosphogypsum and cement have been reported to improve the physicochemical properties of clayey soils. The present study aimed to investigate the behavior of various soils with different particle sizes and chemical and mineralogical compositions in the presence of phosphogypsum and cement mixed at various proportions. These hydraulic binders were assayed on three different soil samples, and their effects were examined using a battery of standardized tests, including the Atterberg limit, uniaxial compressive strength, Californian Bearing Rate (CBR) test, thermogravimetric analysis (TGA), microstructure observation (SEM), and X-ray diffraction tests. The results revealed a significant effect associated with the variation of phosphogypsum content in the soils. Keeping the cement content constant in the mixture, the continuous addition of phosphogypsum was noted to allow shifting the domain of plasticity to the highest water contents, which reduces the sensitivity of the soil to water and to increase the strength of soil. An increase of CBR index with the addition of phosphogypsum and cement is obtained. This treatment could have positively influenced the optimum moisture content and the maximal dry density. The mixture of soilphosphogypsum and cement could give new forms such as ettringite and hydrate indicators of the improvement of the mechanical properties of the soil. This improvement varies from one soil to another, depending on its granularity and its mineralogy. The mineralogical composition of the soil, particularly kaolinite, amount, and size grading, have direct effects on the physical and mechanical properties of the soils under investigation. Keywords Stabilization . Mineralogy . Clayey soil . Phosphogypsum . Cement . Geotechnical properties
Introduction Plastic soils constitute a major problem in the field of road construction. The water sensitivity of these soils, particularly clay soils, is considered as one of the major factors leading to road damages. The chemical stabilization of soils is among the most common technique so far proposed to solve this problem (Cabane 2004). Phosphogypsum has commonly been applied in the presence of hydraulic binders (cement) to enhance the me-
* Hajer Farroukh [email protected] 1
Geoglob Laboratory, Faculty of Sciences, Sfax University, Sokra Road, Sfax 3018, Tunisia
2
Faculty of Sciences of Sfax, Geoglob Laboratory, University of Sfax, Road Soukra km 3.5, BP1171, Sfax 3000, Tunisia
3
Department of Research, Tunisian Chemical Group, Sfax, Tunisia
chanical and geotechnical properties of soils, which can be used as basic or subgrade material in road construction (Sfar 2004). Large amounts of phosphogypsum (PG) are produced annually throughout the world, and increasing concerns h
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