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

本研究的目的是通过分析超声横波的起伏来掌握混凝土从新拌到硬化的特性。对该混凝土质量控制评价方法进行了研究，取得了如下成果。采用弹性模型和粘性模型进行有限元分析，采用弹性模型和粘性模型对超声横波在新拌砂浆中的传播进行了有限元模拟。在此基础上，从动态剪切弹性模数和粘性系数两个方面分析了材料的传输速度和吸收系数。它们与实验测量的值相关联。冷缝产生的无损检测方法实验制作了冷缝放置延迟引起的冷缝，考察了冷缝对超声横波传播的影响。因此，由于冷连接的原因，吸收系数存在差异。试验中考察了配合比、材料、养护温度等因素对试验结果的影响。结果表明，传输速度和吸收系数随时间的变化与凝固性的变化一致，但受上述因素的影响较大。从而证实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.