Stabilization of sand with combined use of lignosulfonate and polyethyleneimine: Water resistance and mechanical properties of treated sand

Lignosulfonate (LS), an environmentally friendly and non-toxic material, has attracted attention as a non-traditional soil stabilizer. However, LS could be easily washed out from soil due to its high water-solubility, which leads to the consequent loss of strength. Therefore, an additional admixture is needed to overcome this limitation. In this study, polyethyleneimine (PEI) was mixed with LS to stabilize silica sand. The consequent improvements in the water-resistant and strength characteristics of LS-treated soil were investigated through the unconfined compressive strength (UCS) test, triaxial test, and cyclic wetting-drying tests. The results demonstrated that the UCS had an increasing trend with a rise in LS content. Moreover, the UCS was influenced by the drying out of the water from the specimen related to the LS concentration and the curing time: a higher concentration and a longer curing duration improve the UCS. According to the triaxial test, the deviatoric stress also increased with the LS content. In addition, both the soil's cohesion and secant elastic modulus were improved in a more ductile manner than typical cemented soil. In the cyclic wetting-drying test, no disintegration of the specimen was observed. Although the UCS of the treated soil in wet condition revealed a notable decrease, after re-dry for seven days in a controlled room, its strength recovered to about 86% of that in its initial dry condition.