Develpoment of Pumpability Testing Machine of Fresh Concrete

本课题致力于新拌混凝土可泵性试验机的研制，两年来的研究成果如下：(1)管流模型混凝土发泡试验方法的建立我们研制了以吸水性聚合物为液相，以轻骨料和焦炭为固相的模型混凝土。设计了保水剂的配合比，使其流动性与新拌混凝土中的实际砂浆相近。管流中的固相可以可视化，跟踪固相的运动。在此基础上，利用视频采集卡和A/D转换器，研制了颗粒运动的时间域测量系统。通过可视化测试的结果，我们可以阐明锥形管道中流动混凝土的变形和堵塞机理以及分叉口中的离析过程。(2)pi…新拌混凝土离析电阻测量系统的研制为了间接反映混凝土中骨料的体积比，我们研制了针对实际新拌混凝土的电阻测量系统。从而提高了电极的耐磨性。根据现场试验结果，提出了流态混凝土离析和临界堵塞条件的评价方法。上述研究成果申请了两项专利。(3)基于可视化试验信息的固液两相流分离模型的开发(1)。建立了流动混凝土的两相流动模型，模拟了新拌混凝土在管流中的离析和堵塞现象。模拟结果表明：(1)锥形药剂加速了固相体积变化的偏析；(2)液体的高粘度导致管内压力较高，具有较高的偏析阻力，从而使总物料具有良好的流动性。较少

This project was concerned with development of pumpability testing mochine of fresh concrete.The results of this project in two years are given as follows.(1) Establishment of vesualized testing method for modeled concrete in pipe flowWe developed modeled concrete, which consists of absorbent polymer as liquid phase and lightweight aggregates and coke as solid phase. Mix proportion of absorbent polymer was designed so that its fluidity was similar to that of actual mortar in fresh concrete. And the solid phase in liquid phase of pipe flow could be visualized to follow the motion of solid phase. Then with the use of video deck and A/D converter, the measuring system of particle motion in time domain was developed. From the results of this visualized test, we could clariify the deformation and blocking mechanism of flowing concrete in tapered pipe and segregation process in bifurcated potion.(2) Development of electrical resistance measuring system for segregation of fresh concrete in pi … More pe flowWe developed the electrical resistance measuring system for actual fresh concrete to represent the volume ratio of aggregates in concrete indirectly. Then the wear out resistance of electrode was improved. From the site experimental results with the use of this measuring system, the evaluation method for segregation and critical blocking condition of flowing concrete was proposed. we applied for two patents on the above developments.(3) Development of segregation model for solid-liquid flow of two phase materialBased on the information from the visualized test (1). two phase model of flowing concrete was developed and the simulation of segregation and blocking of fresh concrete in pipe flow was counducted. From this simulation, the following results were derived.(a) Segregation, defined as the volume change of solid phase, is accelerated in the taper potion.(b) High viscosity of liquid phase leads to the considerable high pressure in pipe and to the high segregation resistance, which results in the good fluidity of total material. Less