混凝土压应力水平对超声声速的影响研究

Research on the influence of concrete compressive stress level on ultrasonic sound velocity

为研究混凝土压应力水平对超声声速的影响,考虑了混凝土强度等级及龄期两种因素,制作了C20、C30、C35、C40、C45五种强度的混凝土标准立方体试块。在龄期为7、14、21、28、35d时,分别对试块进行不同受压状态下的超声检测试验。结果表明:混凝土在受压状态下超声声速随压应力增加呈分段线性减小趋势。根据应力-声速曲线变化规律,提出了三拐点四线性段假定,建立了混凝土受压状态下应力-声速理论模型;该模型可以将压应力状态下混凝土结构超声检测得到的超声声速修正为无应力状态下的超声声速。经试验验证,该模型误差较小。该研究结果揭示了混凝土受压状态下的超声传播特性,为拓展超声检测范围和提高超声检测评定结果精度提供了参考依据。

In order to study the influence of concrete compressive stress level on ultrasonic sound velocity, the concrete standard cube blocks with strength of C20, C30, C35, C40 and C45 were made by considering two factors of concrete strength grade and age. When the age was 7, 14, 21, 28 d and 35 d, the blocks were tested under different compression conditions by ultrasonic testing. The results show that the ultrasonic sound velocity of concrete under compression decreases piecewise linearly with the increase of compressive stress. According to the changing law of the stress-sound velocity curve, the assumption of three inflection points and four linear segments was put forward, and a theoretical model of stress-sound velocity of concrete under compression was established. The model can be used to modify the ultrasonic sound velocity of concrete structure under compression to that under non-stress state. The experimental results show that the error of this model is small. The research results reveal the ultrasonic propagation characteristics of concrete under compression, and provide a reference for expanding the range of ultrasonic testing and improving the accuracy of ultrasonic testing and evaluation results.