著者

清水 寛太 山田 義智 古賀 志門 平野 修也

出版者

一般社団法人 セメント協会

雑誌

セメント・コンクリート論文集 (ISSN:09163182)

巻号頁・発行日

vol.74, no.1, pp.265-272, 2021

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<p>本研究は高流動コンクリートのスランプフロー試験を対象として、機械学習の一種であるランダムフォレストによりフレッシュ性状(スランプフロー値、500mmフロー到達時間、空気量等)の推定を試みた。ここでの学習は、使用材料、混和剤の成分、調合、練混ぜ条件、経過時間などの特徴量(説明変数)を60項目からスタートして、その重要度を評価した。その結果、重要度の高い10項目の特徴量(説明変数)でフレッシュ性状の各値が推定できることを示した。また、推定したスランプフロー値、500mmフロー到達時間より既往の研究成果を基にレオロジー定数を推定し、目視材料分離判定や数値解析による高流動コンクリートの充填シミュレーションに用いることが期待できる。</p>

著者

平野 修也 山田 義智 西 祐宜 崎原 康平

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.85, no.774, pp.993-1003, 2020

被引用文献数

3

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<p> In order to conduct flow analysis of cement-based material such as cement paste, mortar and concrete, it is important to more accurately obtain the rheological constants representing the flow characteristics of the material. In this study, the rheological constants of mortar were measured by two rheology tests. The first was sphere pull-up test, the second was the measurement by using rotational vane viscometer. According to previous studies, the former was able to measure the rheological constants of high fluidity mortar, and the latter was able to evaluate the shear stress characteristics of cement-based material containing fine aggregate and coarse aggregate. Furthermore, in this study, the flow constitutive equation of mortar was derived and Moving Particle Semi-implicit (MPS) method was proposed. Using this MPS method, flow simulation of mini slump flow test was attempted.</p><p> The results obtained from the experimental study and analytical study in this paper can be summarized as follows.</p><p> Throughout the sphere pull-up test, the rheological constants (yield value and plastic viscosity) of mortar which was the same mix proportion as mini slump tested mortar were measured. In the test results, the larger mini slump flow value was, the lower yield value was, and the relationship between the two values was able to be approximated by an exponential curve. On the other hand, plastic viscosity and arrival time at mini slump flow of 115mm had positive correlation, and the relationship between the two values was able to be approximated by a linear function.</p><p> Using a rotational vane viscometer, the flow curve of mortar was measured for various shear conditions. It was confirmed that the flow curves of all mortar samples were able to be approximated by the Bingham model under all shear conditions. And the obtained flow curve was approximated by the Bingham model, and the rheological constants of all mortar sample was determined. Thixotropy was confirmed in the flow characteristics of the mortar sample from the obtained flow curves. Also, contrary to the general tendency, the larger mini slump flow value was, the higher plastic viscosity was for water cement ratio of 30%. It was suggested that the rheological constants measured by rotating vane blade were affected by amplified apparent viscosity of mortar. As a result, the sphere pull-up test was more appropriate for the evaluation of rheological properties of mini slump flows.</p><p> Applying the polygon model to the wall boundary as boundary condition of MPS method, a phenomenon that mini slump flow was shielded by mini slump cone was expressed on the flow analysis. Adopting the rheological constants obtained by the sphere pull-up test, it was attempted that mini slump flow spread of mortar sample was reproduced by MPS analysis. The results obtained by the analysis agreed well with the experimental results of mini slump flow. Moreover, in terms of mini slump shape, the analysis by MPS method largely reproduced the actual measured shape. Furthermore, following the analysis condition used in mini slump flow analysis, mortar flow spread with slump cone was predicted by MPS analysis. The results obtained by the analysis reproduced the actual measured value of slump flow. Therefore, the analysis by MPS method and the rheological constants obtained by the sphere pull-up test are effective in mortar flow spread.</p>