Abstract: The thermal conductivity is a critical parameter of infrastructure materials, which are used as frost-resistant fills in cold regions. The parameter is mainly determined by the material composition. A frost-resistant fill, composed of waste foundry sand (WFS), fly ash (FA), expandable polystyrene (EPS), Portland cement and water, is proposed. ISOMET apparatus is used to measure the thermal conductivity of the fills, in particular, the effect of mixing ratios on the thermal conductivity of WFS-FA-EPS fills. The test results show that the increase of EPS beads, FA or cement results in the decrease of thermal conductivity of the fills. The increase in dry density or moisture contents enhances the thermal conductivity. The components in descending order affecting the thermal conductivity are EPS, FA and water. The increase of water-EPS/FA mass ratio increases the thermal conductivity of materials. The thermal conductivity of investigated specimens ranges between 0.5～1.0 W/m×K, favorably less than that of general geomaterials, e.g., 1.0～2.0 W/m×K.