Macro and microstructural characterisation of waste foundry sand reused as aggregate

In this study, representative samples of waste foundry sand (WFS) from an industrial landfill and steel industries were characterised according to mineral aggregate criteria; these same residues were also characterised microstructurally using optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the WFS have very similar physical characteristics compared to conventionally manufactured sand used in asphalt paving. These residues additionally showed similar petrographic characteristics and less risks of potential alkali-reactivity. The elemental composition revealed a predominance of silica (46–52%), ferrous oxides (3–30%) and carbonaceous materials (2–15%), i.e. elements that would not act as pathogenic agents to the pavement asphaltic matrix if the residues were incorporated into it as aggregates materials. Important benefits generated from this practice include cost reduction in asphalt paving projects, reduction in the use of mineral resources and in the discard of waste, increase in the lifespan of landfills and reduction of environmental contamination.