Effect of initial compaction pressure and elevated temperature on swelling pressure of two Indian bentonites

The present article brought out the effect of compaction pressure and temperature on the swelling pressure of two Indian bentonites. The isochoric swelling pressure tests were carried out using a modified oedometer at ambient and elevated temperatures. The effect of compaction pressure on swelling pressure of compacted bentonite was studied by conducting constant volume swelling pressure tests on two bentonites for a range of dry densities between 1.3 and 1.8 Mg/m³. The effect of temperature on the swelling pressure of bentonites was evaluated by conducting tests on three different conditions, such as isothermal, incremental and decremental temperature conditions. The isothermal swelling pressure tests were performed at three different temperatures such as 25 °C, 55 °C and 95 °C at a dry density of 1.6 Mg/m³. In incremental and decremental temperature conditions swelling pressure tests were performed at various temperatures in a stepwise manner. The effect of temperature on swelling pressure of compacted bentonites was investigated theoretically using Diffused double layer theory. A correlation between the compaction pressure, dry density and swelling pressure of bentonites is presented based on the experimental results. Further the correlation equation was validated with literature-reported results of three bentonites. In isothermal condition, an increase in temperature resulted in increase and decrease in swelling pressure for divalent bentonite-A and monovalent bentonite-B, respectively. In the incremental temperature condition, swelling pressure was found to increase slightly for both the bentonites. During the decremental temperature condition, the swelling pressure was noted to decrease significantly for both the bentonites. The theoretically calculated swelling pressure was found to increase with an increase in temperature for both the bentonites.