There are hopes that production costs and environmental load in foundry works can be reduced by employing the frozen mold which is made by refrigerating a mixture of only sand and water. In this study, the transition of the mechanical properties of the frozen mold as it was being thawed and were examined with the aim of applying the frozen mold to product parts with small heat capacity, such as cores. The compressive strength of a standard frozen mold consisting of only sand and 5mass% water dramatically decreased when it was thawed and the strength could not be recovered by drying. In contrast, another frozen mold produced by substituting colloidal silica solution for water showed some compressive strength even in the thawed state, and the strength increased with subsequent drying, while keeping excellent strength during the frozen state. The reusability of sand when colloidal silica was used for producing the frozen mold was also investigated. The compressive strengths did not deteriorate under any states; frozen, thawed, or dried even though the sand was used repeatedly. The above results prove that frozen molds prepared by mixing sand and colloidal silica solution has the potential to be applied to product parts with small heat capacity, such as cores, and possesses excellent reusability without the need for any screening process, thus contributing to the improvement of environmental load.
