Effect of SCMs on hydration kinetics of Portland cements

Author(s): Barbara Lothenbach, Axel Schöler, Maciej Zajac, Mohsen Ben Haha, Frank Winnefeld
Paper category: Proceedings
Book title: Proceedings of the International RILEM Conference
Materials, Systems and Structures in Civil Engineering 2016
Segment on Concrete with Supplementary Cementitious Materials
Editor(s): Ole M. Jensen, Konstantin Kovler and Nele De Belie
ISBN:978-2-35158-178-0
e-ISBN: 978-2-35158-179-7
Publisher: RILEM Publications SARL
Publication year: 2016
Pages: 86-95
Total Pages: 10
Language : English

Abstract: Blending of Portland cement with limestone or quartz leads generally to an acceleration of the PC reaction, while fly ash can delay the onset of the acceleration period. Investigations using a cement replacement of 50 wt% showed a significant acceleration in the presence of limestone, related to enhanced C-S-H nucleation on calcite. Measurements of the concentrations in the pore solution indicated that this increased nucleation, which facilitates C-S-H formation, results in stronger undersaturation with respect to alite and thus in faster alite dissolution. In general a faster dissolution was observed for those blends where a higher degree of undersaturation with respect to alite was present. Blends with high sulfate and/or high aluminium concentrations in the pore solution reacted slower, indicating that high aluminium and sulfate concentrations can retard alite hydration, thus confirming the results reported from studies on pure clinker phases. The investigations indicate that the mechanisms controlling the early hydration of composite cements are a complex combination of their surface characteristics and their influence on the pore solution composition.

Online publication : 2016
Publication type : full_text
Public price (Euros) : 0.00