Study on rheological properties of concrete using pattern analysis of transfered waveform

本研究的目的是通过分析超声波横波的起伏，建立混凝土从新拌到硬化的性能评价方法，即建立混凝土全龄期力学模型。为了达到上述目的，本文用有限元法分析了超声横波在混凝土试件中的传播特性，并对传播波形进行了模式分析。主要研究结果如下：1.动态粘弹性扭转模型的有限元分析采用动态粘弹性扭转模型对超声横波在混凝土中的传播进行了有限元模拟。在此基础上，对波形、传播速度和吸收系数进行了准确的分析。2.传递波的波形分析通过传递波的功率谱分析了粗骨料对波形的影响，明确了骨料的最大粒径对功率谱的影响。可作为新拌混凝土离析的检测方法。3.混凝土全龄期力学模型采用模量不依赖于时间尺度的动态粘弹性流变模型，对试件在各个频率下的运动进行了分析和试验。作为结果，可以把握从长时间尺度的现象，如蠕变，到短时间尺度的现象，如动态运动的评估方法的可能性。

The purpose of this study was to establish the evaluation method for the properties from fresh to hardened concrete by analyzing the undulation of ultrasonic transversal wave, and in other words to establish the all-age mechanical model of concrete. To achieve above mentioned purpose, properties of Ultransonic transverse wave transfered through concrete specimens were analized by finite element method, and pattern analysis of transfered waveform was accomplshed. Many results were obtained as follows.1.Finit element analysis by dynamic visco-elastic torsion modelTransmitting of ultrasonic transverse wave through concrete was simulated by finite element method using dinamic visco-elastic model. According to this analysis, waveform, transmitting velocity and absorption coefficient were analyzed accurately. And it was clarified that the optimum size of element was to be decided against individual ages of concrete and frequencies of ultrasonic transverse wave.2.Pattern analysis of transfered waveformEffects of coarse aggregate to waveform were analyzed by power spectrum of transferd wave, and it was clarified that maximum size of aggregate affected to the spectrum. It will be applicated as test method of segregation at fresh concrete. And the optimum frequency of wave at non-destractive test using ultrasonic at individual ages were desided by probability density spectrum analysis.3.All-age mechanical model of concreteUsing dinamic visco-elastic rheology model with moduluses that never depend on time scale, movement of specimens were analyzed and experimented at individual frequency. As results, possibility of evaluation method that can grasp from long time scale phenomena, for example creep, to short time scale phenomena, for instance dynamic movement was shown.