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In this research, a by-product of paper and timber industries, lignosulphonate (LS), was used to enhance the properties of expansive clay. Laboratory tests included Atterberg limits, Proctor compaction, unconfined compressive strength (UCS), free swell and unconsolidated–undrained (UU) triaxial compression tests, which were conducted on LS-treated and untreated specimens. Moreover, effects of moisture content changes and cyclic wetting and drying on soil properties were assessed. To illustrate strength creation owing to LS-stabilization, scanning electron microscopy was conducted on unstabilized and LS-stabilized clay. The strength properties of the soil improved with LS-stabilization. For both the treated and untreated soils, strength parameters decreased with increase in compaction moisture content. The swell per cent and swell pressure of the expansive clay reduced owing to LS-stabilization. The reduction of plasticity index of the soil because of stabilization changed the category of soil expansivity from high to moderate. These improvements in soil properties are related to the electrostatic reaction that occurs between the LS–water mixture and soil particles, thus leading to soil aggregation.

This paper presents the swelling and consolidation characteristics of lignosulfonate (LS) stabilized expansive clay. Expansive clay samples of Amol city in Iran have been used in this research. Based on Atterberg limits and uncon ned compressive strength tests, the optimum percentage of LS for the treatment of this clay was determined at 0.75% by soil dry weight. To investigate the swelling and consolidation properties of untreated and LS-treated remolded samples, one-dimensional swell and consolidation tests were conducted on these samples. Test results showed that LS had considerable e ect on the consolidation and swelling behavior of the expansive clay. Moreover, the e ects of compaction water content change and cyclic wetting and drying on the volume change properties of unstabilized and LS-stabilized samples were investigated. Untreated and LS-treated specimens showed di erent consolidation behaviors towards the variations of compaction moisture content due to the alteration of soil expansivity category from high to moderate. The Scanning Electron Microscope (SEM) images of samples showed that the soil speci c area was reduced because of stabilization. This reduction in soil speci c area led to the decrease of a nity of samples to moisture increase; thus, the volume change of expansive clay decreased.

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