The Effect of Replacing Fine Silica with Fine Phosphate Waste (Russaifa mine) on the Compressive Strength of Mortar and Concrete: A Case Study in Jordan

It is known that the dumping of Phosphate wastes from Phosphate factories and mines has a negative effect on the environment. In an effort to reduce dumping, this study examines the possible reuse of this waste as a replacement for the fine sand of silica in mortar and concrete. Phosphate waste replaces silica with the following by-weight percentages- 0%, 10%, 25%, 50% and 100%. To check the feasibility of such reuse, 30 mortar cubes, 30 concrete cubes, and 20 concrete cylinders were prepared for testing to achieve a compressive strength of 25 MPa according to ASTM (211.1-81). The tests performed in this paper are conducted to the following samples- (50 * 50 * 50 mm) mortar samples, (150 * 150 * 150 mm) concrete cubes, and (150 * 300 mm) concrete cylinders. The samples were left in curing for a period of 7 days for some samples, and others for 28 days. The results show that the use of Phosphate wastes increased the compressive strength of mortar by 29%. In concrete cubes, the use of Phosphate wastes increased compressive strength by 26%. In concrete cylinders, the use of Phosphate wastes increased the compressive strength by 34%. Subsequently, it is proposed that the stone squanders of Phosphate be utilized as an alternative to fine silica, and they demonstrated their quality through the basic tests of aggregate. The increase in stone strength is attributed to Phosphate waste as it has less absorption. The increase in the strength of Phosphate sand is due to the presence of chemical substances that increase the strength of its cohesion, such as TCP (Tricalcium Phosphate) (40.72%), P2O5 (Phosphate pentoxide) (18.64%), CaO (Calcium oxide) (28.22%) and SiO2 (Silicon dioxide) (44.45%). The percentage of CL (Chlorine) is minimal (0.01%).