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Rheological behavior of Portland cement pastes during early hydration
This contribution focuses on the structural changes of cement paste from mixing to setting, determined by rheological measurements. Initially after adding of water, the cement starts to hydrate. During the induction period the rate of hydration is very low. The cement paste is still workable and behaves like a fluid. Its viscosity often approximately follows Bingham's law with a yield stress and nearly Newtonian behavior above the yield stress. During hydration, the structure of the cement paste changes, it stiffens, and both yield stress and viscosity increase. By measuring the rheological properties during cement hydration, information on the structural growth during the hydration process can be obtained. But it is important that the structure of the paste is not influenced by the measurement itself. Cement paste before setting is a flocculated suspension that is very sensitive to the applied shear. Its microstructure breaks down very easily. The usual rheological techniques (for example flow curves) are not suitable for a continuous monitoring of cement hydration, as the yield stress of the paste is exceeded during measurement, causing a structural breakdown. With a special dynamic measurement technique, low-amplitude oscillatory shear, the structural growth of a cement paste can be studied continuously from mixing until setting
Rheological behavior of Portland cement pastes during early hydration
This contribution focuses on the structural changes of cement paste from mixing to setting, determined by rheological measurements. Initially after adding of water, the cement starts to hydrate. During the induction period the rate of hydration is very low. The cement paste is still workable and behaves like a fluid. Its viscosity often approximately follows Bingham's law with a yield stress and nearly Newtonian behavior above the yield stress. During hydration, the structure of the cement paste changes, it stiffens, and both yield stress and viscosity increase. By measuring the rheological properties during cement hydration, information on the structural growth during the hydration process can be obtained. But it is important that the structure of the paste is not influenced by the measurement itself. Cement paste before setting is a flocculated suspension that is very sensitive to the applied shear. Its microstructure breaks down very easily. The usual rheological techniques (for example flow curves) are not suitable for a continuous monitoring of cement hydration, as the yield stress of the paste is exceeded during measurement, causing a structural breakdown. With a special dynamic measurement technique, low-amplitude oscillatory shear, the structural growth of a cement paste can be studied continuously from mixing until setting
Rheological behavior of Portland cement pastes during early hydration
Rheologisches Verhalten von Portlandzement-Pasten im Frühstadium der Hydratation
Winnefeld, F. (author)
2002
14 Seiten, 13 Bilder, 2 Tabellen, 15 Quellen
Conference paper
English
Portlandzement , Zementpaste , Abbinden von Zement , Rheologie , rheologische Eigenschaft , Strukturumwandlung , hydraulisches Ansteifen , Fließspannung , Viskosität , dynamisches Messverfahren , kontinuierliche Messung , Einflussgröße , Zuschlagstoff , Abbindeverzögerer , Superplastifizierer , experimentelle Untersuchung
Rheological Behavior of Portland Cement Pastes During Early Hydration
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