Experimental Study On Concrete Performance Undergoing Freeze-thaw Cycles With Different Cryogenic Temperature Ranges

As an important building material for the construction of natural gas storage tanks,concrete will have direct contact with liquefied natural gas(LNG)in engineering applications,and it will be under cryogenic temperature.During the operation of the tank,due to changes in LNG reserves and other reasons,the concrete will experience significant temperature fluctuations,and its mechanical properties change due to freeze-thaw cycles.Among the research productions we have gained,the concrete performance after cryogenic freeze-thaw cycles is seldom discussed,and there is no systematic study on the effect of freeze-thaw cycles of different temperature ranges on the concrete performance.In this paper,the variation law of concrete performance after freeze-thaw cycles of different temperature ranges is studied.Considering that moisture content is one of the main factors that affect the performance of concrete under ultra-low temperature,this paper also makes a comparative analysis about that.This article takes the experiment as the main research method.The repeated freeze-thaw cycles with different temperature ranges of 10℃~-40℃,10℃~-80℃ and 10℃~-160℃ were conducted,and the effects on compressive strength,elastic modulus and peak strain are discussed afterwards.The effect of the water content was analyzed by the same temperature range.The performance were compared to tell the difference of effect of different temperature ranges on concrete performance after freeze-thaw cycles.The results show that at the upper limit temperature of freeze-thaw cycles,the mechanical properties of concrete deteriorate after freeze-thaw cycles.Compressive strength and elastic modulus decrease with the increase of freeze-thaw cycles,while the peak strain increases gradually.The lower the lower limit temperature of the freeze-thaw cycle is,the faster the compressive strength decreases.Howerver,for the elastic modulus and the peak strain,the lower limit temperature of the freeze-thaw cycles is-40 ℃ or-80 ℃ make no difference,and the peak strain decreases in the latter part of freeze-thaw cycles with the temperature range of 10℃~-160℃.At the upper limit temperature of freeze-thaw cycles,the performance of specimen which didn’t go through water soaking after the freeze-thaw cycle changes volatility.At the lower limit temperature of freeze-thaw cycles,the compressive strength,elastic modulus and peak strain of concrete increase and decrease with the increase of freeze-thaw cycles.The larger the temperature range is,the earlier the transition occurs.For the temperature range of 10℃~-40℃,due to the limited number of cycles,the performance showed an upward trend,and for the temperature range of 10℃~-80℃,the transition occurred at the freeze-thaw cycle of 20 times,and for the temperature range of 10℃~-160℃,the transition occurred at about 5 times of freeze-thaw cycles.The performance of specimen which didn’t go through water soaking did not show some obvious trend after freeze-thaw cycles,and the growth rate due to the cooling is limited.This paper explores the performance changes of concrete after freeze-thaw cycles with different temperature ranges,and discusses the relevant microscopic mechanism,which lays the foundation for further research in related fields and provides the basis for the practical engineering application.