Estimation of Defecs in Concrete in Early Age by Using Acoustic Emission Method

本文采用声发射法对混凝土早期干缩、保护层不良和温度应力引起的缺陷进行了调查和评估，并对不同材料、不同配合比和不同钢筋限制率的模型试件在浇筑后28天进行了试验。在试验期间连续测量声发射计数率收缩应变。并将计算结果与强度、杨氏模量等参数进行了比较。结果表明，混凝土试件中产生的拉应力越大，声发射计数率越大。同时对流动体混凝土进行了相同的试验。与普通混凝土相比，流动混凝土的声发射计数率明显偏小。这表明流态混凝土具有很好的配伍性，混凝土早期发展阶段出现的大气孔等缺陷很少。用直线导线法进行空洞探查试验，证实了Tllis的存在。

In this study, defects in concrete causing in early age due to drying shrinkage, and poor casying and thermal stress were investigated and estimated by acoustic emission metod.Model specimens varying materials, mix proportions and the rate of restriction by reinforced bar were tested during 28days after casting. AE count rate shrinkage strain, were measured continuously during the test period. And the results were compared with parameters such as strengths and Young's modulus. From the results, AE count rate became large acording to that the tensile stress causing in concrete specimens became large. And the correlation between AE count rate and the development of defects in concrete in early stage was clearly obseved.At the same time, Same tests for flowing concrete were carried out. AE count rate of flowing concrete was evidently small compared to that of normal concrete. This shows that flowing concrete have very good compativility and the defects in concrete developing in early stage such as large air void are rare. Tllis was confirmed from the air voids obsevation test by linear traverse method.