Feasibility study of copper slag as a structural fill in reinforced soil structures

Copper slag (CS) is a granulated cohesionless glassy material with the appearance of dark black coloured sandy size material. Copper slag is classified as poorly graded sand (SP) as per the Unified Classification System (USCS) and has a specific gravity of 3.6. Copper slag contains iron silicates, calcium oxide, and alumina, with small amounts of copper, lead, zinc, and other metals. The evaluated gradation, physical, shear strength characteristics and electrochemical properties of copper slag met the standard specifications for a structural fill material recommended for use in mechanically stabilized earth (MSE) walls and reinforced soil slopes (RSS). The angle of shearing resistance of copper slag varied between 35° and 49° for loose and dense states, respectively. Thereafter pullout tests were conducted to determine interface apparent coefficient of friction (μS/GSY) between the geogrid and copper slag at normal stresses of 7.3 kPa, 12.5 kPa, 25 kPa and 50 kPa and obtained results are then compared with those of geogrid in reference fill material, Yamuna sand (YS). The pullout tests were carried out as per ASTM Standard D 6706–01(2013) on an apparatus that was fabricated indigenously. This paper addresses the geogrid – copper slag interaction and geogrid – Yamuna sand interaction from pullout tests and demonstrates that copper slag can be effectively used as a structural fill for reinforced soil structures.