Mechanism of Developing Cold Joint in Concrete, Its Pore Structure and Repair Technique
| Project/Area Number |
13650619
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Building structures/materials
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
TANAKA Kyoji Tokyo Institute of Technology, Materials and Structure Laboratory, Professor, 応用セラミックス研究所, 教授 (40016829)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAUCHI Hiroyuki Tokyo Institute of Technology, Materials and Structure Laboratory, Research Associate, 応用セラミックス研究所, 助手 (40313374)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Concrete / Mortar / Placing Joint / Cold joint / Permeability / Environmental Condition / Pore structure / Repair / 水密性 / 打ち足し時間 |
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| Research Abstract |
A time gap in placing between two concrete layers and environmental condition at concrete placing is found out to be the main cause for producing a cold joint in a concrete member. It is because that the first concrete layer started hydration at long interval time before placing of the second concrete layer and at higher temperature. To discuss quantitatively effect of the two parameters, liquid permeability of mortar specimens that were produced at several placing intervals and at various temperatures were measured. The equation for calculating permeability composed of interval time and temperature was proposed on the basis of the experimental results.
As for the effect of outdoor environment on permeability, specimens with cold joints were made at several interval times of placing in summer and winter and the difference in influence of the seasons on formation of a cold joint was discussed. Furthermore permeability of each specimen was estimated by calculation using temperatures of the specimens. The usefulness of the above method to estimate to permeability of a cold joint is also confirmed in an actual field.
A new technique, in which gallium is intruded m pores of a specimen at high pressure and then the distribution of it is mapped by an EPMA measurement, was developed for studying the structure of a cold joint. It was made clear that a discontinuous plane was formed along the cold joint in concrete and it became more noticeable at longer interval time and at higher temperature.
To make a cold joint watertight three kinds of repair agents, mainly composed of magnesium silicofluoride and calcium silicate, were injected in cold joints at low pressure, and their permeability were measured. It was found out that they produced some crystals in cold joints and decreased their permeability. It was also confirmed by the observation of pore structures at the cold joints that the structures became dense.
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Report
(3 results)
Research Products
(17 results)
