Application of lignosulphonate—a sustainable approach towards strength improvement and swell management of expansive soils

Abstract

Long-term material dependency on natural resources has caused a heavy toll on the environment and biodiversity of natural systems. To explore the effectiveness of the usage of unconventional materials in geotechnical applications, an attempt is made towards the application of calcium lignosulphonate, a by-product of the paper industry in soil stabilization techniques in the place of conventional additives such as lime, cement and fly ash. These materials can harm the environment and also increase the carbon footprint due to emissions during their production. The present study focuses on stabilizing a potential expansive soil by using lignosulphonate (LS) in proportions ranging from 0.5% to 3% and 6%. The strength and swell parameters of treated and untreated soil are evaluated under curing periods ranging from 0 to 28 days. The strength aspects of the soil-lignosulphonate composites are evaluated under different moisture states and also after allowing a longer interaction period between LS and soil through the pre-compaction mellowing process. The interaction mechanism is also substantiated with microstructural studies. An average strength improvement of the order of 2 is depicted by the treated soil for an optimum LS content of 1.5%. The treated soil also showed a considerable decrease in swell potential and swell pressure, than untreated soil. The manuscript primarily focuses on the behaviour of LS-amended expansive soil in terms of strength and swelling characteristics and the technique to augment the interaction mechanism of the LS-soil composites.