The Impact of Phosphogypsum on Enhancing the Compressive Strength of CSA-Treated Sand

Abstract

Various additives such as fly ash, lime, fibers, and slag have been explored to enhance soil stabilization characteristics and fulfill specific performance criteria. The utilization of Calcium Sulfoaluminate (CSA) cement has garnered considerable attention due to its environmental friendliness compared to ordinary Portland cement (OPC) and its notable durability and early strength development. This study investigates the impact of replacing CSA with phosphogypsum (PG) on enhancing the compressive strength of sand while exploring the potential for recycling waste from phosphorus production. Chemical composition analysis of PG was conducted through X-ray fluorescence (XRF) and X-ray diffraction (XRD), revealing the predominant presence of calcium sulfate hemihydrate along with impurities like fluorine, phosphorus, silicon, and sulfur compounds. The mixture compositions were initially standardized to include 7% CSA and 10% water content for all samples. Subsequently, five types of mixtures were prepared, with CSA replaced by PG in proportions of 10%, 20%, 30%, 40%, and 50%. Uniaxial compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were conducted at intervals of 3, 7, 14, and 28 days to assess the influence of PG on soil stabilization characteristics. The findings indicate that the optimal replacement level of CSA with PG would be 30%, resulting in the highest strength development after 28 days of curing.