Can waste foundry sand fully replace structural concrete sand?

Foundry sand (FS) waste creates a serious solid waste management problem worldwide due to the high volumes produced, necessitating alternatives to landfilling. A possible route is its use in concrete; however, the current consensus is that FS can only be used for modest sand replacements, based mostly on evidence on concrete with clay-bound FS (greensand). Conversely, this study assessed salient properties of structural concrete with chemically bound FS (polymeric resin binder), for which there is very little information. Concrete mixes were prepared in which FS replaced regular concrete sand partially or fully. The results showed that unlike greensand, the tested chemically bound FS could replace regular concrete sand fully, giving highly workable mixes with good mechanical properties (compressive, splitting and flexural strengths and static modulus of elasticity) similar to those of mixes with regular concrete sand; the effect of FS content on these properties was not statistically significant. Durability in terms of water absorption, carbonation and alkali–silica reaction tests was not adversely affected. The possibility of using high contents of this type of FS in concrete (as opposed to greensand) gives promise for an additional outlet route for large quantities of this waste material with clear economic and environmental benefits.