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.