Soil Stabilization Using Lignosulfonate

Chemical stabilisation of soil using commercial admixtures is a common technique often adopted by industry to improve the behaviour of erodible and unstable deposits such as those forming the subgrade for roads and rail infrastructure. Although traditional alkaline admixtures such as cement, gypsum, lime have been effective in strengthening and stiffening the natural formations of transport and other civil infrastructure, the consequential impact on the soil and groundwater chemistry has been an environmental concern for many years. While being cost-effective, these alkaline and sometimes corrosive admixtures have directly contributed to substantial rise in the soil and groundwater alkalinity (pH about 8-9) apart from the significant reduction in soil porosity (void space) thus adversely affecting the growth and development of certain native vegetation and sub-surface fauna. In contrast, the use of nontoxic lignosulfonates (LS) with much smaller quantities has been reported to achieve similar results without harming the environment.

Lignosulfonate is a soluble dark brown liquid, and it is a by-product of the timber and paper industry. The use of lignosulfonate as a soil stabilizer has significant advantages in relation to traditional admixtures with respect to soil and groundwater environment quality. This is because lignosulfonate is readily diluted in water and causes no pH change in the soil upon treatment. Furthermore, it is also non-corrosive to metals and non-flammable, and classified as nonhazardous. An additional benefit is associated with the reduction of brittle behaviour during shear loading that is well known for alkaline mixtures. This paper showcases a number of applications of LS in controlling erosion and swelling of expansive soil for which the use of lignosulfonate has yielded comparable and in cases superior performance to that of traditional admixtures.