Experimental study on strength, durability, microstructural and environmental performance of soil treated with iron tailing-based geopolymer for sustainable subgrade application

Expansive soils exhibit high compressibility, swelling & shrinkage behaviour, moisture sensitivity, and low bearing capacity, often causing differential settlement and structural damage in pavements and foundations. Although lime and cement stabilization, their production generates significant carbon emissions. This study examines Soil-FeT geopolymer mixtures as a sustainable alternative for subgrade stabilization. Soil specimens were treated with binder contents of 10, 20 and 30%, activated using 6, 8 and 10 M alkaline solutions. Mechanical performance was evaluated through unconfined compressive strength (UCS), split tensile strength (STS), California bearing ratio (CBR), resilient modulus (MR), and hydraulic conductivity tests, while durability was evaluated through 12 wetting‒drying cycles. Geo-environmental performance was examined using leachibility, carbon emission, and energy consumption analyses. Results showed that specimens containing 10% binder activated at 10 M achieved optimum performance, with UCS increasing from 0.23 to 4.89 MPa for low-plastic soil and from 0.11 to 3.81 MPa for high-plastic soil. The soaked CBR values increased approximately 12- and 19-fold compared to untreated soils. Treated specimens exhibited durability, with mass loss below 10%, and satisified IRC subgrade requirements. Heavy metal concentrations remained below USEPA limits. Sustainability assessment indicated 82% lower CO2 emissions and 61% lower energy consumption than cement stabilization, confirming Soil-FeTgeopolymers as an eco-friendly stabilizer for applications.