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USED FOUNDRY SAND AS A RAW MATERIAL FOR THE CONSTRUCTION INDUSTRY

Alena Pribulova, Peter Futas, Jozef Petrik, Peter Blasko, Maria Mihalikova

Abstract

The foundry industry is a major producer of industrial waste, with used foundry sands (UFS) representing the largest share. While bentonite-bonded sands can be reused multiple times, sands with organic binders are typically single-use and are often landfilled due to limited regeneration capacity. Their valorization in construction materials represents an important pathway toward circular economy. This study evaluates the use of UFS from three different foundries, including bentonite- and furan-bonded systems, as partial replacement of natural aggregates in concrete. Five UFS samples were incorporated at replacement levels of 2, 4, 6, and 10 wt.%, while maintaining a constant cement content. Material characterization included particle size distribution and qualitative assessment of residual binder content. Concrete samples were prepared under controlled conditions and cured for 28 days, after which compressive strength was determined and compared with a reference mixture without UFS. The results show that the influence of UFS on compressive strength strongly depends on the origin and binder type. At lower replacement levels (2–6%), selected UFS samples achieved comparable strength to the reference concrete, while higher replacement levels led to a gradual decrease. The most favorable performance was observed for bentonite-bonded sand from Foundry II and furan-bonded sand from Foundry III, indicating that not all UFS exhibit the same suitability for concrete applications. The observed differences are attributed to variations in grain size distribution and residual binder content, which affect the interfacial transition zone and overall matrix compactness. From an environmental perspective, the reuse of UFS can significantly reduce landfill disposal; however, its application must consider potential variability and material-specific limitations. These findings highlight the importance of source-specific evaluation of UFS and demonstrate its potential as a secondary raw material in concrete production.

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