Recycling Foundry Sands in Concrete: A Comparative Study on the Use of Green Sand and Chemically Bonded Sand as Partial Replacements for Natural Sand

Currently, many foundries successfully reuse sand multiple times within their production cycle. However, when the sand can no longer be reused, it is disposed of, resulting in environmental damage and high disposal costs for the company. The present research aims to explore the potential reuse of foundry sands as fine aggregate in concrete. Since this by-product is classified as non-hazardous waste, it can offer interesting opportunities for the recycling of a material that is currently one of the most widely used in the construction industry. This paper studies the potential reuse of green sand (GS) and chemically bonded sand (CBS) as a partial replacement for natural sand (NS) in concrete. Concrete specimens made with 10%, 20%, and 30% of foundry sand were tested, and a comparative analysis was carried out with the standard mixture in terms of chemical–physical properties, workability and mechanical properties. The results showed a reduction in the performance of concrete specimens prepared with foundry sands. The lowest reductions in the strength, which were always below 10%, were observed for a 10% inclusion rate of both GS and CBS, with slightly better performance for CBS. Performance reductions tend to increase with higher replacement rates. However, these performance reductions turn out to be acceptable for concrete used in non-structural applications.