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図書 |
図書
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Peter R. Mouton
目次情報:
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図書 |
図書
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Peter R. Mouton
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図書
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C.V. Howard & M. Reed
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図書
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edited by Stephen M. Evans, Ann Marie Janson and Jens Randel Nyengaard
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図書
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John C. Russ and Robert T. Dehoff
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図書
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John C. Russ
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図書
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Adrian Baddeley, Eva B. Vedel Jensen
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| 8.
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論文
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五十嵐, 心一 ; 池崎, 由典 ; 渡辺, 暁央
概要:
Three-dimensional particle size distributions of unhydrated cement in cement paste were obtained from its two-dimensional cross sections by the stereology analysis. The mean diameter of the unhydrated cement particles was used for
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determining the degree of hydration of cement. The degree evaluated by the average diameters was consistent with those determined by the volume fractions of unhydrated cement and non-evaporable water contents. It was also possible to determine water/cement ratios of hardened concretes, using the hydration degree based on the average diameters and the volume fractions of unhydrated cement particles in concrete at a given age. The particle size distribution of unhydrated cement can be a characteristic feature reflecting the process of hydration of cement.<br />Ex post facto report
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| 9.
論文 |
論文
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米山, 義広 ; 五十嵐, 心一
概要:
Microstructure in cement pastes revealed by BSE image analysis was quantitatively compared with a structure simulated by CEMHYD3D. At a water/cement ratio of 0.25, the spatial structures of unhydrated cement
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particles and coarse capillary pores were sufficiently simulated by the model. At water/cement ratios of 0.40 and 0.60, judging from visual impression, the simulated structures are similar to real ones. However, its geometric features in terms of spatial statistics, especially capillary pores do not agree with the real structure. This discrepancy results from the differences in porosity and pore size to be compared in the two methods. It should be noted that quantitative comparison between real and simulated structures is meaningful only when there are little pore finer than the resolution in each image.<br />Ex post facto report
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| 10.
論文 |
論文
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五十嵐, 心一 ; Igarashi, Shinichi
概要:
(1)セメントペーストの反射電子像の画像解析において,水和反応の進行に伴う構成相の幾何学的特徴の変化を詳細に定量評価することを目的として,2次のステレオロジーパラメーターである2点相関関数を導入した.各構成相の空間分布と位置関係および比表面
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積を評価し,組織の定量評価パラメーターとしての有効性を検討した.各相の2点相関関数は水セメント比や水和度の相違を反映し,残存セメント粒子分布構造と比表面積が水和反応進行過程の情報を担うことが明らかとなった.また,固体構造や粗大毛細管空隙構造の形成が距離を測度として理解され,分布構造の変化を特徴付ける距離の変化はPowersのモデルや不均質組織の代表体積要素の大きさとも矛盾しないことが示された.(2)凝結から硬化にいたる若材齢のセメントペーストの組織変化を観察し,構成相の空間構造の定量評価を行った.高水セメント比の場合はブリーディングにより構成相の分布が不均質になるが,増粘剤の使用や継続的な練り返しにより組織全体は均質化する.また,終結時の固体相の直線経路に関する相関関数はいずれの配合に対してもほぼ一致し,ある一定の連続性を有した固体骨格構造が形成されたときに終結に達する.(3)電子顕微鏡観察像とシミュレーションCEMHYD3Dにより再現された組織の幾何学的特徴の比較を行った.実組織とシミュレーションの水和度が一致する場合,視覚的には実際の観察像と類似のシミュレーション組織が得られ,セメント粒子の空間分布状況を把握することが可能である.しかし,シミュレーションによる毛細管空隙構造は画素寸法による影響を受け,粗大な空隙が直線的に連続する確率は再現されるが,その他の空間分布の特徴は,観察された組織とシミュレーションでは大きく異なることが明らかとなった.<br />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 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.<br />研究課題/領域番号:18560449, 研究期間(年度):2006-2007<br />出典：「コンクリートの微視的構造の評価への高次ステレオロジーパラメーターの導入」研究成果報告書 課題番号18560449 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）) 本文データは著者版報告書より作成
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