Strength improvement of lime-treated clay with sodium chloride

Lime stabilisation of organic clay has often been studied in the past. However, there is some evidence in the literature that the presence of high concentrations of organic matter in clay soil can lessen the chemical reaction between lime and clay minerals and can have detrimental effects on the engineering properties of soil. Hence, in this paper, the stress–strain behaviour and strength properties of organic soil treated with lime and sodium chloride (NaCl) are analysed. A soil mixture, prepared with 5% lime content and 1·5% humic acid, was stabilised with varying quantities of sodium chloride (0·5, 2·0 and 5·0%). Consolidated undrained and drained triaxial tests were carried out on specimens at curing periods of 7 and 28 d with applied confining pressures of 50 and 100 kPa. Scanning electron microscopy and X-ray diffraction analysis were used to observe the microstructural changes resulting from cementation materials. It was found that the introduction of sodium chloride improved considerably the strength properties of the lime-treated organic clay. The microstructural analysis also confirmed the presence of calcium silicate hydrate in a salt-treated organic clay, which was the main contributing factor to the enhanced engineering properties of the clay.