An Experimental Study on Engineering Properties of
Bentonite - Sand Mixtures

Abstract

For the past few decades, compacted bentonite has been considered as potential buffer material in toxic waste disposal repositories because of its low permeability and high swelling capacity. Bentonite has been mixed with sand in appropriate proportions to make bentonite-sand mixtures that are used as backfilling material to seal the galleries of high-level toxic waste disposal repositories. The permeability of barrier should be in the range of 10-8 to 10-10 m/s in the saturated condition. Bentonite from used Bikaner, Rajasthan and local river sand in Rourkela are used for this study.
The maximum dry density and optimum moisture content of bentonite-sand mixtures were determined with variation in bentonite content of 10, 20, 25, 30, 40 and 50% in total weight of the mixture. The permeability of bentonite-sand mixtures was determined using falling head method. For the mixtures having permeability value less than 10-9 m/s, consolidation tests were conducted to find permeability indirectly and to check the permeability values with falling head method results. Based on the permeability results swelling pressure and unconfined compression strength tests were conducted on bentonite-sand mixtures having permeability range of 10-8 to 10-10 m/s in the saturated condition. The test results show that the permeability value decrease where as swelling pressure increases with the increase in bentonite content. The maximum unconfined compressive strength was found for 40% bentonite-sand mixture.