Abstract
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.
Highlights
Sodium chloride was used in conjunction with limetreated organic clay containing 1·5% humic acid
■ The triaxial test results presented in this paper validated the effectiveness of adding sodium chloride, which leads to an increase in the negative excess pore water pressure (Du) and dilative behaviour, resulting in the enhanced effective strength parameters of organic clay
■ The c0 value determined for samples containing 0·5% sodium chloride was equal to 23·6 kPa, which was significantly higher than the value (=7·1 kPa) determined for the samples without any salt (0% sodium chloride)
Summary
There is some evidence in the literature that the occurrence of high concentrations of organic matter, in particular humic acid, in clay soil can weaken the chemical reaction between lime and clay minerals and can have negative effects on the engineering properties of the soil (Chen et al, 2009; Hebib and Farrell, 2003; Kang et al, 2017; Koslanant et al, 2006; Onitsuka et al, 2003; Petry and Glazier, 2004). Sakr and Shahin (2009) demonstrated that soft clay with a high organic content of 14% can be successfully stabilised with 7% lime. Despite a noticeable reduction in the deviator stress after longer curing periods of the lime-treated organic clay (Mohd Yunus et al, 2012, 2013a, 2013b, 2014; Thangavel et al, 2010), the addition of salt resulted in considerable improvement of the specimens.
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