Evaluation of time-dependent-changes of properties of concrete by ultrasonic transfer function analysis

通过对超声横波波动的分析，掌握混凝土从新鲜到硬化的性能。采用该评价方法对混凝土质量进行控制，得到了如下结果：采用弹性和粘性模型，采用有限元法模拟了超声波横波在新鲜砂浆中的传播。在此基础上，从动剪切弹性模量和粘滞模量两方面分析了透射速度和吸收系数。它们与实验测得的值相符。实验中提出了冷接头发生的无损检测方法，并对由于接头放置延迟造成的冷接头进行了实验，考察了冷接头对超声波横波传播的影响。因此，观察到冷接头引起的吸收系数差异。在实验中考察了配比、材料、固化温度等因素对固化效果的影响。澄清了透射速度和吸收系数随时间的变化与沉降的变化相对应，但受上述因素的影响较大。验证了该方法适用于多种混凝土的质量控制。

The purpose of this study was to grasp the properties from fresh to hardened concrete by analyzing the undulation of ultrasonic transversal wave. Many results concerning this evaluating method for quality control of concrete were obtained as follows.1. Finit element analysis by elastic and viscous modelTransmitting of ultrasonic transverse wave inside fresh mortar was simulated by finite element method using elastic and viscous model. According to this analysis, transmitting velocity and absorption coefficient were analyzed from dynamic shearing modulus of elasticity and viscosity. They were corresonded to the values measured by experiments.2. Non-destructive testing method of cold joint occurenceSpecimens include cold joint due to delay fo placing joint were made in experiment, and the effects of cold joint to transmitting of ultrasonic transverse wave were examinated. In consequence, difference of absorption coefficient due to cold joint was observed.3. Applicability of this methodIn experiments, effects of mix proportion, material and curing temperature examinated. And it was clarified that time-dependent-change of transmitting velocity and absorption coefficient corresponded to that of setting, though they were greatly affected by above mentioned items. Thus, it was confirmed that this method was applicable to quality control for many kinds of concrete.