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

本研究旨在借由分析超音波横波之起伏，掌握混凝土从新拌至硬化之性质。通过对混凝土质量控制评价方法的研究，取得了以下成果.采用弹性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，从动剪切弹性模量和动剪切粘性模量两个方面分析了吸声材料的传播速度和吸声系数。它们与实验测得的值相吻合.冷接头发生的无损检测方法实验中制作了因接头放置延迟而产生冷接头的试件，考察了冷接头对超声横波传播的影响。从而消除了由于冷接引起的吸声系数的差异.试验中考察了配合比、原材料、养护温度等因素的影响。结果表明，尽管受上述因素的影响较大，但传播速度和吸声系数的时变性与设置的时变性相对应。因此，证实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.