Eco-engineered soil reinforcement using recycled foundry sand and alkali-treated straw fibers

Stubble burning in northern India exacerbates air pollution, while disposal of Waste Foundry Sand (WFS), a byproduct of metal casting, generates critical environmental burdens. Concurrently, natural clays are characterized by low strength, high compressibility, and susceptibility to large deformations, necessitating stabilization for engineering applications. This study explores the sustainable reuse of WFS and straw fibers to enhance clay performance, aligning with United Nations Sustainable Development Goal 11 (UNSDG11). Experimental programs incorporated 10–40 % WFS and 0.25–2 % straw, with alkali-treated fibers examined for improved bonding. Testing encompassed compaction, consolidation, Atterberg’s limits, unconfined compressive strength (UCS) at variable strain rates, and tensile strength, with durability monitored over 300 days. Results showed maximum densification at 40 % WFS with 0.25 % straw, while peak UCS occurred at 20 % WFS with 1 % straw. NaOH treatment enhanced tensile strength up to 50 %. The findings demonstrate that WFS–straw composites effectively mitigate clay’s inherent weaknesses, offering a sustainable geotechnical solution.