The efficacy of lignosulfonate in controlling the swell potential of expansive soil and its stabilization mechanisms

Many techniques have been developed and applied to prevent and/or remediate infrastructural damage caused by expansive soils throughout the world. Of these techniques, traditional chemical (lime and cement) stabilization has gained world attention because of a good understanding of the underlying mechanisms, availability of technical guidelines, and years of demonstrated field experiences. However, despite the global acceptance of traditional additives for treating expansive soil, other environmentally benign alternatives have been an important subject of research due to the inherent health and safety concerns for traditional admixtures. One such alternative is from the paper industry that manufactures pulp from wood and in the process produces over 50 million tons annually of a waste substance known as lignosulfonate (LS). This substance has been disposed of as a waste product resulting in colossal disposal cost; however, it does have a potential application in geotechnical engineering under the concept of sustainable development. This investigation into LS admixture consists of experimental and theoretical studies. The experimental investigation involved a laboratory evaluation of the efficacy of LS admixture in controlling the swell potential of a remoulded expansive soil. The swell potential was examined in terms of percent swell and swell pressure of the soil. In addition to these engineering properties, the Atterberg limits, unconfined compressive strength, durability (wet/dry and freeze/thaw), compaction characteristics, permeability, consolidation characteristics, and shrinkage behaviours were also investigated. Furthermore, the mechanism by which the remoulded soil was modified or altered by the LS admixture was probed and identified. The optimum content of LS admixture was found to be about 2% by dry weight of the soil. Standard geotechnical laboratory tests performed on untreated and treated compacted soil specimens showed significant and consistent chang