Abstract: The temperature effect on thermal conductivity of compacted Gaomiaozi (GMZ07) and Wyoming (MX80) bentonites was investigated using a thermal probe method. Dry densities and water contents of compacted bentonite specimens were kept constant under constant volume conditions, and then measurements of thermal conductivity were conducted over a wide range of temperatures (5°C to 90°C) by KD2 Pro thermal characteristic analyzer. Meanwhile, the mercury intrusion porosimetry (MIP) tests were also performed to observe the pore-size distributions of compacted specimens. The test results show that at the same water content and dry density, the thermal conductivities of GMZ07 and MX80 bentonites increase with increasing the temperature. When the temperature was 90°C, they can reach 1.2 to 1.5 times of the value at 5°C, due to the enhanced latent heat transfer (LHT) of vapor. At specimen temperature is higher than 60°C, the effect of temperature on the thermal conductivity is more significant than that when temperature is under 60°C. For unsaturated specimens, the temperature effect on the thermal conductivity decreases with increasing the dry density. For a dry specimen, the thermal conductivity hardly changes with the temperature, which is related to the enhancement mechanism of the LHT of vapor. The temperature effect on the thermal conductivity can be explained that the more water vapor and heat transfer paths can be used for LHT, the more obvious the temperature effect on the thermal conductivity.

Key words: bentonite, thermal conductivity, temperature effect, latent heat transfer, mineral composition