Saturated hydraulic conductivity of soils blended with waste foundry sands

Beneficial uses are being sought after for the large quantities of waste foundry sand (WFS) that are landfilled. Potential applications include their use in synthetic soils and incorporation into agricultural soils. In this laboratory study, we investigated the saturated hydraulic conductivity (Ks) of sandy loam, loam, silty clay, and clay soils that were blended with WFS. Each soil was blended with 0% to 50% green sand (bentonite-coated sand) from an iron and aluminum foundry and a phenolic urethane no-bake sand from a steel foundry. The soils and foundry blends were packed into fixed-wall columns, and Ks was assessed using the constant and falling head methods. The results showed that Ks generally increased in a linear manner as the WFS blending ratio was increased in the soils. Compared with soil only, Ks increases were the greatest in the loam and silty clay soils; at 50% WFS, Ks was as much as 235- and 600-fold higher, respectively. However, Ks was lower over the blending range in soils containing green sands that were predominantly coated with sodium bentonite as compared with calcium bentonite. We attribute this to the high swelling properties of sodium bentonite.