Journal Article 点過程としての硬化コンクリート中の気泡の空間分布の評価と気泡間隔の簡便な推定法の提案

室谷, 卓実  ,  古東, 秀文  ,  五十嵐, 心一

Distribution of air voids in concrete was regarded as 2D spatial point processes. Characteristics of their distribution were evaluated by several spatial statistics functions. Furthermore, a characteristic distance between air voids was defined in the nearest neighbor distance function. Correspondence between the characteristic distance and the conventional spacing factor was investigated. Clustered distribution of air voids due to the presence of aggregate particles were properly estimated by the spatial statistics functions. However, as far as the cement paste matrix was concerned, it was possible to assume that air voids were distributed randomly except a range of short distances. Thus, spatial structure of air-void systems, in particular the characteristic distance between air voids could be simply simulated as a random point process. Furthermore, the characteristic distance of real air-void distribution was almost the same as the conventional spacing factor. Compared to the conventional spacing factor that is obtained by following the ASTM C457 procedure, the characteristic distance is quite easy to obtain. Furthermore, taking account of the fact that the characteristic distances measured for real distribution in concretes are plotted within the 95% confidence interval of binominal random point process, air-void systems in concrete can be assumed as 2D Poisson point process. Thus, a simple equation to obtain the spacing factor from a point process was proposed. The spacing factor was correctly estimated by the equation. Therefore, the characteristic distance of air voids defined in this study can be used as a new distance parameter between air voids, alternatively it may be used as a parameter to estimate the traditional spacing factor. コンクリート中の気泡の分布を点過程とみなし,分布の特徴と距離特性の評価を行った.気泡量を変化させた種々の気泡系に対し最近傍距離関数から特性値を定義し,従来の気泡間隔係数との対応を検討した.その結果,気泡は見かけ上凝集性の分布を示すが,セメントペーストマトリックス内ではある程度の距離以上にてランダム分布と見なせ,シミュレーションにてその分布を再現できることを確認した.また,そのランダム分布の特性値は気泡間隔係数と同等の値を与え,その理由を気泡間隔係数が定義される3次元規則配置下での距離の同義性から説明した.また,点密度と配合から気泡間隔係数を簡便に推定できることを示した.空間点過程としての取り扱いは,新たな気泡構造評価法もしくは気泡間隔係数推定の有用な手段になりうると考えられる.

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