Strength and Microstructural Characterisation of Plastic Soil Under Freeze and Thaw Cycles

Abstract

In India, Himalayan region experiences least temperature during winter season. Temperature within range of − 25 °C is common at high-altitude areas like Jammu and Kashmir (India). A large number of experiments have been conducted in the past to investigate the consequences of addition of waste materials and different fibres on engineering properties of different soils. In contrast, out of them few research works have been done to quantify the durability of plastic soils against freeze–thaw (FT) effect, which mostly occurred in this region. This experimental study was performed to investigate the unconfined compressive strength and durability (mass loss) of plastic soil against 3, 5 and 10 cycles of FT in open condition. The Taguchi method was used for design of experiment (DOE), a standard L9 orthogonal array formed with three factors, and three degrees were chosen; 3–6% eggshell powder (ESP), 0.05–0.15% polypropylene fibre (PPF) and 2–6% sodium chloride (NaCl) by total dry weight of mixture of soil and additives were used to prepare the specimens. Experiments were conducted on both parent and treated soil specimens. Experimental results were analysed by performing analysis of variance. Finally, optimised conditions were experimentally verified. Stabilisers improved the strength by 129%, 32% and 143% for 3, 5 and 10 FT cycles in optimum conditions with respect to parent soil samples. The values of mass losses for 3, 5 and 10 FT cycles in optimum conditions were found 7.4%, 6.22% and 1.53%, respectively. Microstructural analysis and elemental composition showed significant changes in soil specimens in harsh conditions. Results obtained from this study might be used for subgrade improvement in pavement construction in cold region areas as ESP, PPF and NaCl were used to minimise the loss of inherent strength of soil. All stabilisers are natural or non-hazardous. So, the research promises an environment friendly and economical solution for the soil strength-related problem associated with cold regions.