Recycle waste foundry sand in concrete efficient use of natural sand resources

Purpose and goal

This was a pilot study aimed to use foundry waste sand in concrete. The long term idea is to lower the environmental impact and create a resource effective and environmentally driven competitiveness. The results show that many foundry sand types are excellent as concrete aggregates and that the produced concrete has good properties. It is also showed that this leads to a lower environmental impact, and that it is profitable for both foundry and concrete producer.

Results and expected effects

Using foundry waste sand, bonded with chemical binders, as fines in concrete works great. In most cases, the resulting concrete has properties quite similar to concrete produced with ´traditional´ sand. Bentonite bonded foundry sand (´greensand´) results in concrete with - in short - inferior properties. There is usually less environmental impact when foundry sand is used in concrete, compared to the sand being used as landfill. Calculations show that both foundries and concrete producers can get higher profits when the sand is used in concrete.

Approach and implementation

The project contained three steps. The first step was a basic characterisation of the physical, mineralogical and chemical properties of different types of foundry sand. In the second step, concrete was produced with different foundry sand replacing the ´standard´ finer sand. Finally, LCA and LCC calculations, comparing the alternatives ´use the sand on landfills´ and ´use the sand in concrete´, were performed.