基于压电阻抗技术监测混凝土强度发展的实验研究

本文基于压电阻抗（EMI）监测技术，对混凝土立方体标准试块的强度发展进行了监测。制作3种不同配合比的标准试块，将压电片粘贴于标准试块表面和埋置于体内，用精密阻抗分析仪HP4294A提取压电片在不同养护龄期时的电导纳信号，并测试相应标准试块的抗压强度。试验结果表明，随着混凝土养护龄期的增长，表面粘贴和体内埋置两种压电片的电导频谱均发生了变化，但是变化形式不同。对表面压电片，得到了其共振频率的变化量与标准试块抗压强度之间的定量对应关系；对内置压电片，通过引入指标δ建立了电导频谱与标准试块抗压强度的定量关系。本文工作表明采用EMI技术监测早龄期混凝土在硬化过程中强度发展是一种可行且可靠的无损检测方法。

Tests for monitoring strength development of concrete based on EMI technique

Based on the electro-mechanical impedance (EMI) sensing technique, experimental investigations were carried out to monitor the strength development in concrete. Three batches of concrete test cubes with different mixture design were prepared. For one of each batch of concrete test cubes, one piezoelectric patch was surface bonded and another piezoelectric patch was embedded. An impedance analyzer HP4294A was used to extract the admittance signals during the curing age of 3-28 days and the compression tests were conducted simultaneously. The experiment results showed that the conductance signals changed during the curing age for both bonded and embedded piezoelectric patches but with different forms. For the bonded piezoelectric patches, a quantitative relationship was established between the shift of the fundamental frequency and the compressive strength of the cubes; for the embedded piezoelectric patches, a quantitative relationship was also presented between the conductance signals and the compressive strength of concrete test cubes through the employment of the index .This work showed that monitoring the strength development in concrete by EMI technique is feasible, reliable and nondestructive.