RHEOLOGICAL MODELING FOR CONCENTRATED FLOCCULATED SUSPENSIONS CONSIDERING THE EFFECT OF PRIMARY PARTICLE SIZE DISTRIBUTION

Autor: Suguru Gotoh, Masanobu Ando, Toyoharu Nawa
Rok vydání: 2013
Předmět:
Zdroj: Cement Science and Concrete Technology. 67:587-594
ISSN: 2187-3313
0916-3182
DOI: 10.14250/cement.67.587
Popis: The rheology of fresh concrete is strongly dependent on the rheology of cement paste. Due to the coagulation or flocculation, cement paste shows complex non-Newtonian behavior such as yield stress, thixotropy and so on. For coagulated suspensions, a lot of rheological models based on fractal concepts have been proposed. The authors have adopted the rheological model for concentrated and flocculated suspension proposed by Chougnet, et al., in combination with the breakup model of flocs in a shear field developed by Muhle and the viscosity model proposed by Mills. In this study, the effect of primary particle size distribution（PSD）on the fluidity of suspensions was established based on the rheological model. The viscosity of concentrated suspensions was determined by the effective volume fraction of flocs and the random packing fraction. The effective volume fraction was estimated by the balance between the coagulation due to attractive interparticle forces and the fracture in the shear field with the fractal concept. The random packing fraction was calculated from the primary particle size distribution using the random packing model for multi-component particles proposed by Suzuki et al. Considering the random packing fraction, mean diameter from the PSD and the fractal dimension for each suspension, the model predictions were in good agreement with experimental flow curves with various PSDs.セメントペーストなど凝集性のサスペンジョンは複雑な流動挙動を示す。著者らはその粘性を予測するために、フラクタルな凝集体の形成と破壊に基づくレオロジーモデルを検討してきた。本研究では、試料ごとの粒子充填率の変化を鈴木らのランダム充填モデルから求め、その変化を粒度分布の影響として粘度発現モデルに組み込むこととした。また、粒度分布より得られる平均粒径を用いて、DLVO理論、水和力の考慮より粒子間力を算出した。モデル中の比例係数Kについては、粒度分布より求められるランダム充填率と平均粒径を用いて決定した。その結果、フラクタル次元を適切に推定することで、その流動挙動を予測できることを示した。
Databáze: OpenAIRE
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