Assessment of Combined Effects of Lignosulfonate and Fly ash in Enhancing the Geotechnical Characteristics of Swelling Clays

The present study introduces an eco-friendly approach to repurpose waste from the paper and wood industry as a construction material. The method involves a unique combination of lignosulfonate (LS) and fly ash (FA) to address the limitations of using fly ash / lignosulfonate as a stand-alone stabilizer for expansive soil. Two synthetic soils, namely, Soil A (20% bentonite and 80% sand, by weight) and Soil B (20% bentonite and 80% fly ash, by weight) were chosen to represent the soil of high plasticity. A different dosages of calcium LS (1–3%, in the interval of 1%) was mixed with synthetic soils to understand the efficacy of LS and FA in stabilising montmorillonite-based clay soils. Several geotechnical properties of untreated and treated swelling clays, including plasticity, swelling pressure, consolidation parameters, and unconfined compressive strength were examined followed by microstructural studies. The results conclude that the combination of FA and LS has significantly improved the geotechnical properties of swelling clays and is quite effective compared to lignosulfonate and fly ash as a standalone stabilizer. Moreover, the presence of fly ash has reduced the lignosulfonate requirement to stabilize the swelling clays.