EXPERIMENTAL STUDY ON THE COMPRESSIVE STRENGTH OF CONCRETE UNDERGOING FREEZE-THAW CYCLE ACTIONS WITH DIFFERENT ULTRALOW TEMPERATURE RANGES

Through freeze-thaw cycle action experiments of concrete with ultralow temperature ranges of 10℃ to -40, 10 to℃℃ -80 and 10 to℃℃ -160,℃ the effect of different ultralow temperature ranges on the concrete compressive strength is investigated. From these test results, it can be shown that for the specimens undergoing various freeze-thaw cycles at different ultralow temperature ranges, their failure modes are basically in a double cone shape when they are loaded at upper and lower limit temperatures. But the sound during their destruction processes and failure conditions are different. The variation regularity of the compressive strength of concrete undergoing freeze-thaw cycle actions under ultralow temperatures is obviously different from that at natural environment temperature. The effect of the freeze-thaw cycle action for various ultralow temperature ranges on the concrete compressive strength is also different. The concrete compressive strength will increase at the initial stage of the freeze-thaw cycle action for these temperature ranges with the lower limit temperatures which are relatively higher. After that, they fluctuate and trend to a deteriorating state with the increase in number of freeze-thaw cycles. There are obvious differences among different ultralow temperature ranges for the single freeze-thaw cycle action damage index and the cumulative freeze-thaw cycle action damage index of concrete. For the temperature ranges with the lower limit temperatures which are relatively higher, they are still positive after experiencing more freeze-thaw cycles at lower limit temperatures, but are always negative after several freeze-thaw cycles for those with the lower limit temperatures which are relatively lower. It shows that the cumulative damage of concrete due to the freeze-thaw cycle action for the latter is more severe than that for the former. The results in this paper can provide references for reliably designing concrete structures of liquefied natural gas storage tanks and so on.