Physical and geotechnical long-term properties of lignosulfonate-stabilized clay: An experimental investigation

This research investigates the effect of Lignosulfonate (LS), timber and paper industries by-product, in improving physical and geotechnical properties of high plasticity clay from the Amol city in the Mazandaran province, Iran. Long-term behavior of unstabilized and LS-stabilized clay by using direct shear tests were evaluated. In addition, the effect of wetting and drying cycles on the results of direct shear and unconsolidated-undrained (UU) triaxial tests was investigated and compared together. Addition of LS by aggregation of clay particles, enhanced the physical and strength properties of the clay. The effect of LS-stabilization on the internal friction angle of the soil was negligible (only one degree increase). The major part of the improvement in long-term strength of the soil, was due to increased cohesion between soil particles (from 1 to 7 kPa). Also, test results revealed that wetting and drying cycles has no considerable effect on the UU triaxial test results (up to 1.86% decrease in maximum deviatoric stress). However, in the direct shear tests, the samples are more affected by wetting and drying cycles (up to 37% decrease in peak shear strength). Scanning electron microscopy (SEM) micrographs revealed that due to the stabilization, the structure of clay was changed from a particle base to an aggregated form. In fact, in this case, the pores in the soil structure have been reduced, which has led to strength increase.