Recyclability of molding sands compacted with inorganic binders

Inorganic binders, especially those based on sodium silicates and geopolymers, are gaining relevance and represent a promising alternative for the foundry industry as a more sustainable option compared to traditional organic binders.

By lacking carbon in their molecular structure and using water as a solvent, these compounds drastically reduce the emission of volatile organic compounds and therefore offer several health and environmental benefits. By producing fewer gas emissions, they also provide benefits related to part quality, with less gas-induced porosity and good dimensional accuracy.

However, another important advantage of inorganic binders is worth highlighting: a lower charge of contaminants in the sand residue after demolding, being 90% lower than in sands bonded with organic resin.

Sand recovery tests conducted within the framework of the LIFE GREEN CASTING project have shown that, using thermomechanical methods, inorganic agglomeration systems allow for easy recovery with a utilization rate exceeding 90%.

Similarly, the research team has also characterized the residual sand that cannot be reused in the casting process. In this case, the sand is classified as “NON-HAZARDOUS” waste, making it acceptable for landfills for non-hazardous waste types B1b and B3.

However, the characteristics of this waste stream, with its low organic matter content (0.401%) and low Total Organic Carbon (TOC <0.2%), also allow to be used as a secondary aggregate in construction applications. This makes it possible to reuse it in the manufacture of cement, bricks, or other similar applications.