Develpoment of Pumpability Testing Machine of Fresh Concrete

本项目是关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)模拟混凝土管流试验方法的建立我们研制了以吸水性聚合物为液相、轻骨料和焦炭为固相的模拟混凝土。吸水性聚合物的配合比设计应使其在新拌混凝土中的流动性与实际砂浆的流动性相近。管流液相中固相的运动轨迹可以直观地显示出来。利用视频卡和A/D转换器，研制了颗粒运动时域测量系统。通过可视化试验研究，可以明确锥形管内流动混凝土的变形和堵塞机理，以及分叉处的离析过程。(2)混凝土离析电阻测试系统的研制 ...更多信息 我们研制了实际新拌混凝土电阻测量系统，间接表征混凝土中骨料的体积比。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。我们已就上述发展申请两项专利。(3)基于可视化试验信息的固液两相流分离模型的建立（1）建立了流动混凝土的两相流模型，对新拌混凝土在管流中的离析和堵塞进行了模拟。从该模拟中，得出以下结果。(a)偏析是指固相体积的变化，在锥形部分加速了偏析。(b)液相粘度高，管内压力高，抗离析能力强，使整个物料流动性好。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