The Influence of Superplasticizer and on the Hydration of C3A and Cement

• Main Authors: Lee, Lung-Ling, 黎瑞玲
• Other Authors: Li Tau
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/06868504211221810551

碩士 === 國立中央大學 === 土木工程學系 === 84 === The hydration of cement has a great influence on the workability of high performance concrete (H.P.C.) as well as its setting, such as strength and durability. Therefore, it''s very important to understand and control the dynamic properties and hardening rate of cement during hydration. In applying materials, high performance concrete has to add chemical admixtures like superplasticizer in order to improve the workability, rheological behavior, lowering the amount of water and decreasing microstructure air void of concrete. At present there are many brands of superplasticizer, among which the ingredients, characteristics and moculer weight are widely different, Further, cement is composed of four main clinker, each of which has different and sophisticated mechanism of hydration. When these materials are combined to be HPC, it will affect with each other. Consequently, by measuring concentration of pore solution,heat evolution of hydration, the change of setting time, matching experiments like adsorption behavior and X ray diffractrometry analysis to examine the influence of superplasticizer to hydration of C3A and cement materials, in order to have a better imformation of the application strategy of every materials. The result of this research shows that obviously C3A affects the early hydration and setting of concrete; the amount of gypsum also affects the hydration of C3A. Adding superplasticizer cement will delay the process of hydration because of SP adsorption. Besides, slowing phenomenon is more apparent along with the increasing of dosage. As a result, the best dosage is about 1~2% weight as many of cement. C3A and cement adsorb superplasticizer''s adsorption equilibrium time is different, but its tendency is similar; the curves of isothermal adsorption all belong to monolayer adsorption. In C3A system, the amount of SP adsorption is dependent on the amount of gypsum, while in cement system, it depends of the amount of C3A and sulfate. The amount of gypsum determines the morphology of C3A hydrated; adding superplasticizer will also delaying hydration of C3A and the producing rate of hydrate.