Influence of Temperature on the Engineering Properties of Selected Tropical Black Clays

Abstract

Laboratory tests were carried out to examine the effect of temperature on the engineering properties of selected tropical black clays (known as black cotton soils, BCS) in Northeastern Nigeria. Black cotton soil was sourced from two borrow pits in Numan and Biu and each subjected to geotechnical investigations. Soil samples were subjected to high temperatures of 25, 50, 75, 100 and 150 \({^{\circ }}\)C for 240 min, respectively. Natural soils were classified as A-7-6(15) and A-7-6(11) for Numan and Biu black cotton soils, respectively, using the AASHTO soil classification system. Tests carried out included Atterberg limits, free swell, compaction and California bearing ratio. Statistical analysis was carried out on the obtained results using analysis of variance with the Microsoft Excel Analysis Tool Pak Software Package to determine the levels of significance of the effect of temperature variation on the properties of the soil. Mini-tab R15 software and XLSTART 2014 statistical tool incorporated as an add-in in Microsoft Excel were used for the regression modeling and correlation analysis, respectively. Test results showed a decrease in liquid limit and plastic limit, an increase in maximum dry density, with a corresponding decrease in the California bearing ratio. No general trend was established for plasticity index and optimum moisture content. Generally, results of the statistical analysis showed that temperature has significant effect on the tested soil samples and positively improved the engineering properties of the selected soil samples. Based on results obtained, an optimal temperature of 100 \({^{\circ }}\)C is recommended for remediation and improving the geotechnical properties of the treated soils.