I'm working on a project with a company that uses sand casts during moulding processes and they provided us with samples of the sand they use before it's involved in the procedure and afterwards (Waste foundry sand). I'm wondering if there's specific parameters regarding grain size for using WFS as an aggregate for concrete mixes, my samples led me to believe that most of the WFS this company produces is about 1/2 mm to 1 mm in diameter. A brief literature review has offered no conclusive results and little information regarding specific gran diameter in WFS. Is this byproduct suitable for concrete mixing? Any help would be greatly appreciated.
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Waste Foundry Sand (WFS) can be partially used as a fine aggregate in concrete mixes, especially in eco-friendly or experimental concrete designs.
Based on literature and comparative studies (similar to our work with dolomite powder replacements), the ideal particle size of WFS is typically in the range of 0.1 mm to 1.0 mm. Your sample (0.5–1 mm) falls within a usable range. However, uniform gradation, absence of residual binders, and low clay content are critical to avoid strength reduction.
In our own research on Functionally Graded Concrete (FGC), replacing part of cement with finely powdered dolomite showed strength variation depending on mix design and placement zone (compression vs tension). A similar testing framework can be applied for WFS:
Use 10–30% replacement of fine aggregate (sand) with WFS
Monitor changes in compressive strength, water absorption, and workability
Test at 7, 14, and 28 days to see hydration behavior
If WFS has low harmful impurities and is well-graded, it can be a good substitute — especially in non-structural or eco-blended concrete applications.
For full results, I’d recommend controlled batching and curing, along with grain analysis by sieve testing. Feel free to ask if you’d like a sample mix design or testing layout.
Civil Engineer
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