Engineering Properties of Bentonite Modified with Lime and Gypsum

This paper presents the engineering properties such as compaction, unconfined compressive strength, consistency limits, free swell index, California bearing ratio and consolidation of bentonite stabilized with lime and modified with gypsum. The content of lime and gypsum was varied from 0 to 10% and from 0.5 to 8%, respectively, to check the improvement in the engineering properties. The results of this study revealed that the dry unit weight and optimum moisture content of bentonite + 8% lime increased with the addition of 4% gypsum. The unconfined compressive strength of bentonite did not change with the increase in curing period. The unconfined compressive strength of bentonite + 8% lime increased with the addition of 4% gypsum. Beyond 4%, the unconfined compressive strength decreased. The unconfined compressive strength of bentonite-lime-gypsum mix increased with the increase in curing period. The liquid limit, plastic limit and free swell index of bentonite + 8% lime decreased; whereas the plasticity index increased with the addition of 4% gypsum. The California bearing ratio and modulus of subgrade reaction increased for bentonite stabilized with 8% lime and modified with 4% gypsum leading to reduction in earth work and required thickness of subgrade bentonite. The coefficient of consolidation of bentonite increased with the addition of 8% lime and did not change with the addition of 4% gypsum. The swell potential of bentonite + 8% lime increased with the addition of 4% gypsum. The improved behaviour of the bentonite-lime-gypsum mixture will boost the construction of road pavements on such problematic soils

Potential of Bentonite-lime-mix Modified with Phosphogypsum and Reinforced with Sisal Fibres

The paper presents the potential of bentonite-limephosphogypsum mix reinforced with sisal fibre in effectively reducing the pavement thickness in an extremely problematic sub-soil condition intended for road construction. In view of which, compaction, unconfined compressive strength and California bearing ratio tests were conducted. The content of lime, phosphogypsum and sisal fibre was varied from 0 to 10%, 0 to 10% and 0 to 2% respectively. The specimens were prepared at their respective optimum moisture content and maximum dry unit weight for conducting the unconfined compressive strength and bearing ratio tests and were cured for 3 to 28 days. The results of this study reveal that the unconfined compressive strength and bearing ratio of the bentonite-lime-phosphogypsum mix increased with the increase in curing period. Addition of sisal fibres to the bentonite-limephosphogypsum mix changes the behaviour of the composite from brittle to ductile in the post peak region. Scanning electron micrographs and energy-dispersive X-ray analysis confirms the improvement in unconfined compressive strength and bearing ratio. The improved behaviour of the composite indicates that the sisal fibres have the potential for use in road pavements