| Project/Area Number |
18560449
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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 Shinichi Kanazawa University, Graduate School of Natural Science and Technology, Professor (50168100)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Stereology / Two-point function / Structure distance / Representative volume element / Setting / Permeability / Simulation / Spatial statistics / 透水係数 / 高性能AE減水剤 / 凝結遅延 / 個体骨格構造 / 連続性 / 画像解析 / 反射電子像 / 分散性 / 2点間直線経路相関関数 / クロス相関関数 |
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| Research Abstract |
1. The two-paint functions for unhydrated cement and coarse capillary pores were not influenced by the magnification of the SEM examination. The magnification generally used in the backscattered electron image analysis for cement pastes covers sufficient area as the representative volume element, which is necessary for unbiased evaluation of the amount of each constituent phase Continuity of a phase could be characterized by the lineal path function. Reduction in the continuity for cement particles and capillary pores was expressed as decreases in the lineal path function with time. The evolution of solid skeleton in the pastes was also represented by the increase in the path function. The distance of negative correlation in the two points cross function between cement particles and pores was greater at high water/cement ratios. The distance increased with time at high water/cement ratios whereas there was little increase in the distance at an extremely low/water cement ratio of 025. T
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hese tendencies reflect characteristics in the deposition of hydration products around unhydrated cement particles. At high water/cement ratios, the greater degree of hydration of cement resulted in the thicker layers of inner hydration products around the cores of unhydrated cement particles. This led to the greater distance of the negative correlation.
2. Effects of bleeding and the addition of superplasticizer on spatial distribution of constituent phases in cement pastes were investigated by backscatter based SEM examinations. Heterogeneous distribution of the phases was observed in cement pastes with a water/cement ratio of 0.60. Such heterogeneity due to bleeding was not found in cement pastes with anti-washout admixture. Spatial features of microstructure and degrees of hydration of cement in the cement pastes with the admixture were almost the same as those in the middle part of a specimen without the admixture. Therefore, the middle part in the admixture-free specimen may be regarded as a representative area for the high water/cement ratio even when the bleeding occurs. Setting times of cement were apparently delayed by the addition of superplasticizer. However, degrees of hydration in cement pastes with the superplasticizer were greater than in a cement paste without the admixture. Furthermore, all the cement pastes with different dosages of the superplasticizer had the same lineal path function for the solid phase at the final setting times. It was confirmed by the two point function that cement pastes attained to the final set when certain continuity for solid phase was developed at microscopic scale.
3. Microstructure revealed by SEM-BSE image analysis of cement pastes was compared with a simulated structure generated by the CEMEHYD3D hydration simulation model. The spatial dispersion of unhydrated cement particles was well simulated by the model. However, spatial features in capillary pore structure in the cement paste are not well represented by the simulation. This disagreement results from the differences in porosity as represented by the two methods. Only coarse pores are detected in the SEM examination while the total capillary porosity and its whole spatial structure are virtually simulated in the model. Care must therefore be taken in interpreting agreement of simulation models and their comparison with real microstructures. Less
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