膨润土热传导性能时效性试验研究

Experimental study on aging effect on bentonite thermal conductivity

在不同初始条件下试验研究了静置时间对高庙子钠基膨润土GMZ07和MX80膨润土压实样热传导性能的影响。在保持试样干密度和含水率不变情况下,将不同初始状态试样分别静置1、5、30、60、100d,随后采用热探针法进行热传导系数测试,并对部分试样进行压汞试验。试验结果表明:GMZ07和MX80膨润土的热传导系数均随静置时间的增长而减小,静置早期热传导系数减小较快,随着静置时间延续,热传导系数逐渐趋于稳定。在相同干密度下,静置时间引起的热传导系数减小量随含水率的增大而增大。结合压实膨润土试样的微观孔隙结构变化,认为膨润土热传导系数随静置时间发生变化的主要原因是:试样静置过程中,蒙脱石发生水化膨胀,部分土中水转变成热传导性能较差的惰性水,导致膨润土的热传导系数减小。

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.