Quantifying suitability of waste foundry sands from different metal castings for geotechnical applications

Sand is a rapidly depleting natural resource due to increasing demand as construction material. Waste foundry sand (WFS), an industrial by-product from metal foundries, can satisfy some of the demand. The chemical and physical characteristics of WFS vary depending on the metal casting. The objective of the present study is to quantify the suitability of WFS from different metal castings for geotechnical applications. WFS from gunmetal, iron, cast iron and aluminium metal casting are considered. A comparison of physical, engineering, leaching, pH, morphological and chemical characteristics is done with respect to natural silica sand. Results show that leachate of WFS from gunmetal and aluminium casting is hazardous. There is about a 35% loss in silicate content after each casting type compared to natural silica sand. The angle of friction from consolidated drained direct shear test ranges from 32 degrees to 37 degrees, which is comparable to natural sand. Drainage properties reveal the favourable conditions of WFS to be used in earth-retaining structures. It is concluded that WFS can be used as a replacement for natural sand as a geomaterial for techno-economic benefits.