Sustainable High‐Performance Green Concrete Utilizing Untreated Spent Foundry Sand: Microstructural Analysis, Mechanical Properties, and Durability

ABSTRACT During metal casting processes, large quantities of Spent Foundry Sand (SFS) are generated as waste, making its proper disposal a current research focus in industrial solid waste management. This study investigates the suitability of SFS by replacing natural river sand at equal mass ratios of 5%, 10%, 15%, and 20% to produce green concrete, with subsequent testing of compressive strength (CS), splitting tensile strength (STS), and chloride ion permeability. The results demonstrate that in terms of mechanical properties, at 28 days of curing, a 15% SFS substitution achieved maximum increases of 26% in CS and 12.87% in STS compared to control concrete. Regarding durability, the 28‐day SFS green concrete showed a 7.2% to 17.7% reduction in electrical flux relative to the control group. A recognized limitation is the use of SFS from a single source; future work should validate these findings with SFS from varied origins and include statistical robustness analysis. Furthermore, SEM/EDS analysis revealed that SFS primarily functions as a pore‐filling material without generating new hydration products. These findings indicate that using untreated SFS as a river sand substitute in concrete production reduces manufacturing costs and environmental pollution and enhances mechanical performance and durability. This “zero‐treatment” strategy provides a direct, scalable, and genuinely circular pathway for industrial waste valorization, demonstrating significant potential for large‐scale, sustainable concrete production.