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横波的波动，建立混凝土从新鲜到硬化的性能评价方法，即建立混凝土的全龄期力学模型。为实现上述目的，采用有限元方法对超声波横波在混凝土试件中的传递特性进行了分析，并完成了传递波形的模式分析。结果如下：1。采用动力粘弹性扭转模型，采用有限元法模拟了超声横波在混凝土中的传播。在此基础上，对波形、发射速度和吸收系数进行了准确的分析。明确了单元的最佳尺寸应根据混凝土的龄期和超声横波频率来确定。传递波形的模式分析利用传递波的功率谱分析了粗骨料对波形的影响，明确了粗骨料的最大粒径对谱的影响。该方法可作为新拌混凝土的离析试验方法。通过概率密度谱分析确定了不同年龄超声无损检测的最佳波频。混凝土全龄期力学模型采用不依赖于时间尺度的动态粘弹性流变模型，对试件在不同频率下的运动进行了分析和试验。结果显示了从蠕变等长时间尺度现象到动态运动等短时间尺度现象的评价方法的可能性。

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.