BASIC STUDY ON THE VISCOSITY CHANGE PROCESS OF CEMENT PASTE BY FLOCCULATION AND HYDRATION

Abstract

In order to understand the flow characteristic of fresh concrete, it is necessary to understand the flow characteristic of cement paste. Cement particle flocculation and hydration reactions are considered to be the main factors that influence the rheological characteristics of cement paste. However, experiments on cement paste are inadequate to verify the relation between flocculation or hydration reactions and rheological characteristics. The purpose of this study was to determine the effect of cement particle flocculation on viscosity changes process in cement paste. Moreover, the impact of an early hydration reaction on viscosity changes process was also explored. Microscopy was employed to evaluate the relation between the cement paste’s flocculated state and its viscosity change process. In contrast, the influence of hydration was examined by first utilizing a super plasticizer（SP）to remove flocculation effects from the cement paste, where cement particle dispersion was controlled by the mixture ratio of the super plasticizer（SP）. Maintaining the dispersion state, viscosity changes process over time were then evaluated. Furthermore, the amount of ettringite─which is produced as a byproduct of the early hydration reaction─was measured by X-ray diffraction, and its relations to the viscosity change process and hydration processes over time were also established.本研究は、セメント粒子の凝集がセメントペーストの粘度変化に与える影響について検討を行うとともに、初期の水和反応がペーストの粘度変化に与える影響についても検討した。凝集状態の影響については、粒子画像による凝集状態の評価と、粘度変化の測定結果の関係について考察した。水和による影響については、まず、凝集による影響を取り除くため高性能AE減水剤を使用し、粒子が分散状態となる調合を検討した。次に、その調合において分散状態を維持しつつ、経過時間に伴う粘度変化を求め、その結果を水和反応の影響として評価した。さらに、X線回折によりエトリンガイトの測定を行い、水和の進行と粘度変化との関係についても検討した。