Reference : Compatibilités et incompatibilités liants cimentaires / superplastifiants
Dissertations and theses : Doctoral thesis
Engineering, computing & technology : Multidisciplinary, general & others
Compatibilités et incompatibilités liants cimentaires / superplastifiants
Nicolas, Edwige [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit]
University of Luxembourg, ​Luxembourg, ​​Luxembourg
Université Henri Poincaré - Nancy, ​​France
Docteur en Sciences de l'Ingénieur et Docteur en Chimie du Solide
Waldmann, Danièle mailto
Lecompte, André
[en] polycarboxylate ettringite ; incompatibility orthorhombic C3A ; rheology calcium sulphates ; ball measuring system
[en] Currently required concrete strength imposes a lower water/cement ratio and use of superplasticizer to make easier the fresh material implementation. Polycarboxylate type products are very effective in the short term but can lead to a fast loss of workability in case of binder/superplasticizer incompatibility. The object of this work is the identification of cementitous phases involved in these rheological variations. Initially, flow of various superplasticized pastes is evaluated by a rheometer fitted with a ball measuring system. Compatible combinations flow like a Bingham’s fluid. An incompatibility results in an increase of yield stress and plastic viscosity or rheological properties evolution into Herschel-Bulkley’s fluid. Then, cement/superplasticizer combinations are characterized by rheological tests. Stiffening assessment of pastes and chemical characterisation of hydrated cements show that consistency is associated with amount and microstructure of formed ettringite. These parameters depend on initially present aluminate phase and calcium sulphates. Finally, study of synthetic cementitous systems states that calcium sulphates solubility, in presence of superplasticizer, is increased probably because Ca2+ ions complexation by polycarboxylates. As for the orthorhombic variety of aluminate phase, more reactive than cubic variety, it leads to a large amount of needle-shaped ettringite.

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