Effect of wetting-drying cycles on swelling behavior of lime stabilized sand-bentonite mixtures

In the present study, influence of wetting-drying cycles on swelling pressures of sand-bentonite mixtures used in the construction of sanitary landfills to have an impermeable liner was investigated before and after lime treatment of the mixtures. Swelling pressure tests were conducted to see if the swelling pressures were affected by wetting-drying cycles. First series of specimens were prepared as a mixture of sand and bentonite only. In the first series of specimens, sand was mixed with bentonite in various proportions with their optimum water contents and compacted by using standard proctor energy. In the second series of the specimens, lime in various proportions was added to the mixtures of sand-bentonite. Then, the sand-bentonite mixtures stabilized by lime were compacted with the standard proctor energy at their optimum moisture contents. Five wetting-drying cycles were performed on each specimen and values of swelling pressures were measured at the end of each cycle. Results of swelling pressure tests indicated that the swelling pressure is decreased when lime is added to the mixtures. In addition, decrements were observed on swelling pressures by wetting-drying cycles. The results of the experiments of this investigation showed that the beneficial effect of lime stabilization to control the swelling pressures was partly lost by the wetting-drying cycles. However, the test results indicated that the swelling pressures of the specimens made of sand-bentonite mixtures stabilized by lime were lower than the swelling pressures of the specimens made of only sand-bentonite mixtures.