Abstract: Aging effect on thermal conductivity of Gaomiaozi (GMZ07) and MX80 bentonites with different water contents and dry densities were investigated in this paper. Water contents of compacted bentonite specimens were kept under constant volume condition during curing periods of 1, 5, 30, 60 and 100 days, and the measurements of thermal conductivity were conducted on two bentonites using a thermal probe method. The mercury intrusion porosimetry (MIP) tests were also performed to observe the pore-size distributions of compacted specimens. The test results show that the thermal conductivities of GMZ07 and MX80 bentonites decrease with increasing aging time, the thermal conductivities decrease significantly at early curing periods and then tend to be constant when the aging time exceeds a given day. The aging effect on thermal conductivity increases with increasing water content for the same dry density. According to the change in microstructure of compacted bentonite specimens with aging time, it is considered that the aging effect on thermal conductivity may be attributed to the smectite hydration during the aging process. With the hydration, part of soil water turned into “inert water” with poor heat conduction property, which leads to a decrease in thermal conductivity of bentonites.

Key words: bentonite, thermal conductivity, aging effect, microstructure, smectite hydration