混凝土劈拉过程中的阻抗参数变化规律初步研究

Preliminary Study on Change Law of AC Impedance Characteristics of Concrete During Splitting Tensile

针对混凝土裂缝损伤演化及其检测,提出了一种基于交流阻抗谱法,根据材料阻抗特性参数进行裂缝检测或损伤评估的思路。采用钢筋作为电极,以混凝土的阻抗幅模量(z值)和相角值(φ值)作为材料阻抗特性参数,利用MT4090 LCR测量仪测量混凝土试件在劈裂抗拉过程中阻抗特性参数变化规律。根据测量结果分析混凝土损伤演化发展过程与阻抗特性参数之间的变化规律。试验结果表明:在混凝土劈拉破坏过程中的微裂缝缓慢扩展、劈裂裂缝快速发展、劈裂裂缝不断扩展等3个主要阶段,裂缝发展演化特点有显著的差异,每个阶段测得的z值、φ值变化情况与其对应的裂缝演化特征呈现出稳定的相关性;混凝土z值、φ值随着损伤程度的增大而增大,且两者增大速率一致;混凝土初始z值、φ值与强度之间存在一定线性相关关系。因此,混凝土z值、φ值等电化学参数可以用于检测混凝土裂缝演化和评估其内部损伤程度。

A method based on AC impedance characteristics of concrete was put forward for crack detection and damage assessment. Using the steel bars as electrodes,three groups of concrete specimens with different strengths were designed for splitting tensile testing,and both the impedance amplitude（ z） and phase angle（ φ） were measured by MT4090 LCR measuring instrument during testing. The results showed that there are significant differences in crack evolutionary among the three phases of splitting tensile process,meanwhile,the change law of value of z and φ is closely related to the crack evolution characteristics in the different phases. With the increase of the damage degree,the values of z and φ increase consistently in same rate. There is certain linear relationship between the initial value of z,φ and the strength. The method of crack detection and damage assessment by the electrochemical parameters may come true.