2002 Fiscal Year Final Research Report Summary
A Basic Study on Microstructure and Chloride Diffusivity of Deteriorated Concrete due to Construction Defects
| Project/Area Number |
12650467
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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 |
土木材料・力学一般
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| Research Institution | Akita National College of Technology |
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Principal Investigator |
SAKURADA Ryoji Akita National College of Technology, Department of Civil Engineering, Associate Professor, 環境都市工学科, 助教授 (60290699)
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| Co-Investigator(Kenkyū-buntansha) |
MARUYAMA Kyu-ichi Nagaoka University of Technology, Department of Civil Engineering, Professor, 工学部・環境建設系, 教授 (30126479)
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| Project Period (FY) |
2000 – 2002
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| Keywords | construction joint / chloride-ion / rapid chloride permeability test / pore volume / microcrack / 打継ぎ |
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| Research Abstract |
This study reveals that the effect of pore structure on chloride-ion migration into the deteriorated concrete due to construction defects. Rapid drying of hardened concrete and construction joints, which may give problems in lowering of water-tightness, are picked up here as factors of construction defaults.
For this purpose, the rapid chloride permeability test was employed in the evaluation of chloride-ion penetration into mortar, and the pore size distributions of mortar matrix were analyzed by a probability density function. The main findings from the results can be summarized as follows.
(1) The pore size distribution of dried concrete can be statistically explained by Weibull distribution function. The shape parameter depends on drying temperature. The elevation of drying temperature induces a larger volume of capillary pores in the range of 50nm-2μm in diameter, ruling strongly the chloride-ion diffusivity based on the information of the capillary pore volume and the statistical parameters. A simplified prediction model of chloride-ion migration into concretes is established that could have an applicable to a broad range of drying conditions.
(2) An increase in pore volume ranging from about 1nm-10μm in diameter of the construction joint is remarkable for the mixture of higher water-cement ratio. The construction joint produces difference of chloride diffusion coefficient between joint zone and non-joint zone at early ages. Although the difference decreases with time, the values of the chloride diffusion coefficient along the joint surfaces are slightly higher than that of non-joint zone even at later ages.
(3) The chloride-ion diffusion coefficient of mortar using unhydrated cement, which is recovered from fresh cement paste by freeze-drying, is 20% higher than that of mortar using ordinary portland cement.
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Research Products
(24 results)
