Experimental Study On Temperature Distribution And Thermal Parameters Of Concrete Under Cryogenic Temperature

Nowadays,with the deterioration of the environment and the being adjusted energy structure,the “Clear Energy”such as Liquid Natural Gas(LNG)and so on takes a larger proportion and develops rapidly.LNG tanks are being built to store LNG,which suffer cryogenic temperature cooled to-165℃.Above of all,it is significant to figure out the temperature fields of concrete structures under cryogenic temperature in order to design them in a reliable way.The existing research results mostly focus on concrete mechanical properties,but few have a discussion on the thermal properties.Although there are many studies and achievements about temperature fields at normal temperature and high temperature,it is still necessary to conduct experiments to investigate concrete unique thermal properties under cryogenic temperature.According to existing research results on temperature fields of concrete,our cryogenic concrete research team start a deep study about the rules of concrete temperature distribution and thermal parameters based on the experiments on 4 kinds of concrete mix proportions.The major factors are chosen as cryogenic temperature effect conditions,specimen dimensions,concrete mix proportions and the moisture contents.The cryogenic temperature effect conditions include cooling,heating,and various rates of temperature cooling and heating.The concrete moisture contents are changed via soaking in water and warming to evaporate.Based on the experiment results and existing methods to temperature fields,the numerical iterative approach is used to make numerical inversion calculation.The formulas of concrete thermal parametersat cryogenic temperature are concluded with the assistance of the concrete finite element model analysis and calculation.The results of temperature experiments and numerical calculation prove to be that the concrete temperature distribution is affected by cooling or heating rates,specimen dimensions and moisture contents.The results from two temperature action ways,cooling and back to room temperature,have great difference.And the temperature cooling and heating rates are the main factor which determine the time to a certain temperature for internal points in concrete specimens,the internal temperature gradient as well.The numerical iterative calculation turns out to be that the heat transfer coefficient and specific heat of concreteare linearly related to the cryogenic temperature.For another,the specific heat of concrete is linearly related to its moisture content,while the heat transfer coefficient of concrete is little affected by its moisture content.This article concludes a formula for concrete thermal parameters via these experiments and numerical calculations,which includes cryogenic temperature and moisture content.The rule and formula provided are simple and clear,which conform to the actual situation as well.These results can provide a support and reference for the design,construction and safety assessment of the concrete structures suffered from the effects of cryogenic temperature.