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.