2005 Fiscal Year Final Research Report Summary
Quantitative evaluation of microstructure in concretes by SEM-BSE image analysis
| Project/Area Number |
16560398
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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 |
Civil engineering materials/Construction/Construction management
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| Research Institution | Kanazawa University |
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Principal Investigator |
IGARASHI Shin-ichi Kanazawa University, Graduate School of Natural Science and Technology, Associate Professor, 自然科学研究科, 助教授 (50168100)
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| Co-Investigator(Kenkyū-buntansha) |
KUBO Yoshimori Kanazawa University, Graduate School of Natural Science and Technology, Research Associate, 自然科学研究科, 助手 (50324108)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Back-scattered Electron Image / Image Analysis / Powers-Brownyard Model / W / C Estimation / Internal Curing / Stereology / 3D Particle Size Distribution / Diffusion Coefficient |
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| Research Abstract |
Major results obtained in this research are as follows ;
1. The degrees of hydration of determined by the BSE image analysis were consistent with the Powers model. The volume fractions of each constituent phase can be calculated by the combination of BSE image analysis and the Powers model.
2. Lower W/C ratios and the addition of mineral admixtures resulted in less fine capillary pores.
3. The gap-graded pore structure in which the volume of fine capillary pores is quite smaller than that of large pores, affects the development of compressive strength.
4. There exists a good correlation between compressive strength and the coarse capillary porosity measured by the image analysis.
5. Coarse capillary pore structure revealed by the image analysis reflected differences in mix proportions, ages and curing conditions.
6. The presence of larger amounts of fine capillary pores in cement pastes with silica fume may be responsible for greater autogenous shrinkage in silica fume-containing concrete at
… More
early ages.
7. The gel-space ratio theory by Powers and Brownyard can be applied to cement pastes containing mineral admixtures such as silica fume and fly ash. However, the ultimate strength extrapolated from the theory is smaller in the admixture-containing cement pastes than in the ordinary cement pastes with the same water/binder ratio. This results from the greater volume ratio of coarse pores to the total porosity in the cement pastes with the extenders.
8. Water cement ratios of hardened concretes can be estimated by the proper combination of the image analysis and the degree of hydration determined by the non-evaporable water content.
9. The 3D particle size distribution of unhydrated cement was obtained from the 2D distribution by the Saltykov method.
10. The mean diameter in the 3D distribution can be used as a parameter of degree of hydration of cement.
11. Water cement ratios of hardened concretes can be properly determined by a combination of the mean diameter and the degree of hydration.
12. Diffusion coefficients of cement pastes with and without admixtures were obtained by the solvent exchange method. There was a good correlation between the coefficients and characteristic diameters in coarse capillary pore structure.
13. Effects of the internal water supply on microstructure around the water reservoirs were examined by the image analysis. The image analysis showed that the distance to supply water from the reservoir is at most few hundred micrometers. Less
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