Recent Investigation on the Use of Foundry Sand in Mortar Mixtures

This paper describes how the used foundry sand (UFS) represents the highest amount of solid waste generated by foundries. At present, the general trend is disposal in landfills with two drawbacks: consumption of new raw materials and saturation of existing landfills. This material is classified non-hazardous and therefore its reuse is possible in several industrial sectors. In this study laboratory tests are presented regarding the reuse of waste foundry sand in mortar production by partly replacing the fine aggregate with UFS. The waste material was physically and chemically characterized and then it was added to mortars as fine aggregate replacement at dosage rates of 0%, 20%, and 30% sand by weight. At the dosage of 20%, an addition of previously washed UFS was also considered. The resulting washing water was used to manufacture cement pastes in order to investigate the effect of soluble UFS ions on the hydration kinetics of cement by thermogravimetric analysis. The obtained results showed that the addition of UFS decreases the compressive strength of mortars by about 30%, regardless of the addition rate, and has an accelerated setting effect on cement paste hydration. These undesirable effects are partially mitigated by using previously washed foundry sand.