Ultra-fast NMR imaging of aggregate motion in highly flowable fresh concrete

高流动性新拌混凝土骨料运动的超快核磁共振成像

• 批准号: 07455178
• 负责人: YAMAMOTO Yasuhiko
• 金额: $ 4.61万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455178/
• 关键词: NMR imaging; highly flowable concrete; aggregate motion; NMR映像

Technique of NMR imaging was applied to measurement of aggregate behavior in a fresh concrete flow in a conic pipe. The amplitude and gradient echo methods were combined to detect the particle motion in an arbitrary cross-section of the solid-liquid multiphase flow. A series of experiments proved usefulness of the technique in this sort of study, although a pipe with a small radius of 20mm had to be employed from constraint of the present NMR equipment. Another problem is in time resolution for a flow with Reynold's number exceeding 0.01.A water solution of cellulose ether (with small amount of copper-sulphate added) and elliptic particles of plastics were used as model mortar and aggregate, respectively, to compose model concrete. Variation in cross-sectional image of the highly viscid flow was analyzed to investigate meandering motions of solid particles as well as fine structures of complicated unsteady liquid-phase flow. All these data obtained will be summarized in the form of a final report.Mean flow patterns of model concrete observed were compared with those from the Hagen-Poiseulle and conic-pipe flow theories, and it proved that the former theory provides an acceptable estimation at least for such a gradually tapered pipe. Probability of flow blockage due to aggregate arch formation was studied through a number of experimental runs, and it was concluded that the volume rate of aggregate is a main factor to cause the blockage rather than the viscosity of liquid-phase.Application of the echo-planar method will permit measurement with higher time resolution. Incorportation of the spatial tagging method in large scale experiments may possible enables quantitative evaluation of material segregation indices, where sphere-shaped model aggregate has to be employed for stabilization of magnetic field.

NMR成像技术用于测量圆锥管中新鲜混凝土流中的聚集体行为。将振幅和梯度回声方法组合在一起，以检测固定多流动流动的任意横截面中的粒子运动。一系列的实验证明了这项研究中该技术的有用性，尽管必须从当前NMR设备的约束中使用具有20mm半径的管道。另一个问题是在雷诺数数量超过0.01的流量的时间分辨率中。纤维素醚的水溶液（添加了少量的铜硫酸盐），塑料的椭圆​​形颗粒分别用作模型砂浆和聚集物，以组合模型混凝土。分析了高度粘质流动的横截面图像的变化，以研究固体颗粒的曲折运动以及复杂的不稳定液态相流的精细结构。所有这些获得的数据将以最终报告的形式进行总结。观察到的模型混凝土的均值流量模式与Hagen-Poiseulle和Conic-Pipe Flow Theories的模型混凝土进行了比较，并证明了前者理论至少为这种逐渐锥形的管道提供了可接受的估计。通过多次实验运行研究了由于骨料拱形形成而导致的流动阻塞的概率，得出的结论是，聚合的体积速率是导致阻塞而不是液相粘度的主要因素。回声平面方法的应用将允许使用较高时间分辨率进行测量。在大规模实验中空间标记方法的不关联可能可以实现材料分离指标的定量评估，其中必须使用球形模型骨料来稳定磁场。

项目成果

H.Kyotoh,et al.: "Blockage machanisim of model concrete in a taper tube by nuclear magnetic resonance methods" Int.Conf.on Urbam Eng.in Asian Cities in the 21st Century,Thailand. Vol.I. D87-D92 (1996)

H.Kyotoh 等人：“通过核磁共振方法对锥形管中模型混凝土进行堵塞机械”，21 世纪亚洲城市 Int.Conf.on Urbam Eng.，泰国。

H.Kyotoh,et al.: "Blockage mechanism of model concrete in a taper tube by nuclear magnetic resonance methods" Int.Conf.on Urban Eng.in Asian Cities in the 21st Century,Thailand. vol.I. D87-D92 (1996)

H.Kyotoh 等人：“核磁共振方法对锥形管中模型混凝土的堵塞机理”21 世纪亚洲城市城市工程国际会议，泰国。

H.Kyotoh, D.V.To, Y.Serikawa, T.Yamamoto, K.Kose, H.Nishimura and Y.Yamamoto: "Blockage mechanism of model concrete in a taper tube by nuclear magnetic resonance methods" Int.Conf.on Urban Eng.in Asian Cities in the 21st Century, Thailand. Vol.I. D87-D92

H.Kyotoh、D.V.To、Y.Serikawa、T.Yamamoto、K.Kose、H.Nishimura 和 Y.Yamamoto：“通过核磁共振方法研究锥形管中模型混凝土的堵塞机制” Int.Conf.on Urban Eng