不同超低温及其再回至常温时混凝土受拉强度试验研究

Experimental Study on Tensile Strength of Concrete Subjected to Different Ultralow Temperatures and Returning to Room Temperature

本文通过由常温分别降至-40℃、-80℃、-120℃、-160℃和-190℃及其再回至常温时混凝土劈裂抗拉试验,探讨经历不同超低温混凝土在其超低温时以及再回至常温时受拉强度及其离散性变化情况。结果表明,随作用的超低温降低,混凝土超低温时受拉强度及其离散性分别呈不断地增大和波动状减小趋势,而经历超低温再回至常温时受拉强度呈波动状且基本上较为稳态的变化趋势、未出现恶化迹象,其离散性则呈先减小后增大的趋势;混凝土超低温时与经历超低温再回至常温时的受拉强度比值始终小于1且基本上呈减小趋势,但其变异系数比值则呈增大趋势;超低温时及其再回至常温时的各温度区间混凝土受拉强度变化率变化较为复杂,但其变异系数变化率的变化趋势却相近,均随超低温区间的上下限温度降低逐渐地增大。本文的试验结果可为LNG储罐类混凝土结构设计及其安全性能评估提供依据。

Through the tensile tests of concrete subjected to different cryogenic temperatures(-40℃,-80℃,-120℃,-160℃ and -190℃)and returning to room temperature,the tensile strength and discreteness of concrete subjected to different ultralow temperatures and returning to room temperature from ultralow temperatures are discussed.The test results show that with the decrease in cryogenic temperature,the tensile strength of concrete at ultralow temperature increases continuously,and its discreteness decreases in fluctuation.While the tensile strength of concrete subjected to returning to room temperature from ultralow temperature shows a steady change trend without any sign of deterioration,and its discreteness first decreases and then increases with the decrease in cryogenic temperature.The ratio of tensile strength of concrete at ultralow temperature to for returning into room temperature from ultralow temperature is always less than 1 and basically decreases,but the ratio of their variation coefficients increases.The variation rate of concrete tensile strength at various ultralow temperature ranges and for returning to room temperature from ultralow temperature is complicated.However,the trend of the variation rate of the variation coefficient is similar,which increases gradually with the decrease in the upper and lower limit temperature of the ultralow temperature ranges.The experimental results in this paper can provide reference for the design and safety performance evaluation of the concrete structures as cryogenic temperature storage tanks.