APPLICATION OF PHOSPHOGYPSUM IN SOIL STABILIZATION

Abstract

In order to increase the soil stabilizing capabilities and reach the performance standards that have been set, numerous additives, including fly ash, lime, fibers, and slag, have been subjected to significant research and analysis. There is a task for engineers to find sustainable and cheap alternatives to traditional stabilizers. Calcium Sulfoaluminate (CSA) cement has gotten a lot of attention because it is better for the environment than regular Portland cement (OPC), it hardens quickly, and it lasts a long time, however it is very expensive. To tackle this problem phosphogypsum (PG), industrial waste, can be used to partially replace CSA and reduce costs of the final material. The purpose of this study is to evaluate the impacts of replacing CSA with phosphogypsum (PG) to improve the compressive strength of sand while also addressing the possibilities for recycling waste that is produced during the manufacturing of phosphorus and identify the optimal proportions, which has not been done previously. An examination of the chemical composition of PG was carried out with the assistance of X-ray fluorescence (XRF) and X-ray diffraction (XRD). The results of this investigation revealed that calcium sulfate hemihydrate was the predominant component, in addition to impurities such as fluorine, phosphorus, silicon, and sulfur compounds. Standardized combination compositions were constructed, with CSA being partially replaced by PG at substitution levels of 10%, 20%, 30%, 40%, and 50%. These mixture compositions contained 3%, 5%, and 7% CSA and 10% water. The study assessed how PG affected the ability of the soil to hold its shape by measuring its uniaxial compressive strength (UCS) and ultrasonic pulse velocity (UPV). These experiments were carried out at curing intervals of 3, 7, 14, and 28 days. In addition, scanning electron microscopy (SEM) was utilized to investigate the microstructural alterations that were responsible for the observed increase in strength. According to the results, the best replacement level is reached when 30% of the CSA is replaced with PG. This replacement level gives the best compressive strength after 28 days of curing. The results of this study demonstrate the dual benefits of increased soil stabilization performance and sustainable recycling of industrial wastes.