Valorisation of waste foundry sand as a fine aggregate in one-part alkali-activated concrete

Waste foundry sand (WFS), a by-product generated at approximately 0.6 t per tonne of metal produced, is generally disposed of in landfills after its utility in metal casting ends. To address sustainable waste management and resource conservation, the development of one-part alkali-activated concrete (OPAC) incorporating WFS as a complete replacement for natural fine aggregate was investigated. The OPAC was formulated using blast-furnace slag fine powder as the primary precursor and anhydrous sodium silicate as the activator. Mix proportions were designed for M30 grade concrete under ambient curing conditions, eliminating the requirement for external water curing. Mechanical properties, including compressive, flexural and tensile strengths, were evaluated at 1, 7 and 28 days. The optimum mix achieved a compressive strength of 37.51 MPa within 7 days, demonstrating significant early-age strength development. Durability was further assessed through sulfate and chloride resistance, carbonation depth and drying shrinkage, which confirmed the material’s stability. Environmental performance was analysed using embodied energy and life cycle assessment, highlighting a reduced environmental impact. Paver blocks were successfully cast from the optimum mix. Overall, the results demonstrate OPAC with 100% WFS to be a sustainable, durable and high-performance alternative to conventional concrete for modern construction.