1996 Fiscal Year Final Research Report Summary
Ultra-fast NMR imaging of aggregate motion in highly flowable fresh concrete
| Project/Area Number |
07455178
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
土木材料・力学一般
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| Research Institution | University of Tsukuba |
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Principal Investigator |
YAMAMOTO Yasuhiko University of Tsukuba, Institute of Engineering Mechanics Professor, 構造工学系, 教授 (40061220)
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| Co-Investigator(Kenkyū-buntansha) |
KYOTOH Harumichi University of Tsukuba, Institute of Engineering Mechanics Associate Professor, 構造工学系, 助教授 (80186345)
NISHIMURA Hitoshi University of Tsukuba, Institute of Engineering Mechanics Professor, 構造工学系, 教授 (00010819)
KOSE Katsumi University of Tsukuba, Institute of Applied Physics Associate Professor, 物理工学系, 助教授 (60186690)
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| Project Period (FY) |
1995 – 1996
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| Keywords | NMR imaging / highly flowable concrete / aggregate motion |
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| Research Abstract |
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.
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