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Influence of rheology modifying admixtures on hydration of cementitious suspensions

  • The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed Addition time of PCE SPs on hydration of cement and tricalcium aluminate (C3A) pastes, investigated by isothermal heat flow calorimetry. For cement pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. With delayed PCE addition the cement shows a less retarded setting than with simultaneous addition. The alteration caused by PCE is much more pronounced for C3A and gypsum mixes than for cement. If the SP is added simultaneous, the exothermic peak of C3A is retarded. However, with delayed addition of SP the hydration is shortened, the gypsum depletion is fastened and the exothermic peak occurs less retarded orThe presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed Addition time of PCE SPs on hydration of cement and tricalcium aluminate (C3A) pastes, investigated by isothermal heat flow calorimetry. For cement pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. With delayed PCE addition the cement shows a less retarded setting than with simultaneous addition. The alteration caused by PCE is much more pronounced for C3A and gypsum mixes than for cement. If the SP is added simultaneous, the exothermic peak of C3A is retarded. However, with delayed addition of SP the hydration is shortened, the gypsum depletion is fastened and the exothermic peak occurs less retarded or even accelerated compared to simultaneous addition. It is obvious that for C3A pastes there is less retardation the later the Addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. The rate of reaction in the second stage is lower, discernible in decreased slopes and broader peaks. Besides this, a distinct ramp in the C3A heat flow curves within the first stage of C3A hydration occurs for all pastes with delayed addition of SP, which suggests an accelerated ettringite formation.zeige mehrzeige weniger

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Metadaten
Autoren/innen:Claudia Crasselt, Wolfram Schmidt, Heinz Sturm
Persönliche Herausgeber/innen: M. Tyrer, E. Ganjian, A. West
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Proceedings of the 38th Cement and Concrete Science Conference
Jahr der Erstveröffentlichung:2018
Organisationseinheit der BAM:6 Materialschutz und Oberflächentechnik
6 Materialschutz und Oberflächentechnik / 6.6 Nano-Tribologie und Nanostrukturierung von Oberflächen
7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.4 Baustofftechnologie
Herausgeber (Institution):Coventry University & Cementious Material Group, Institute of Materials Minerals and Mining London
Verlagsort:Coventry, UK
Erste Seite:64
Letzte Seite:67
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:C3A hydration; Cement hydration; Polycarboxylate ether
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Materialien und Stoffe
Veranstaltung:38th Cement and Concrete Science Conference
Veranstaltungsort:Coventry, UK
Beginndatum der Veranstaltung:10.09.2018
Enddatum der Veranstaltung:11.09.2018
ISBN:978-1-84600-088-1
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:20.09.2018
Referierte Publikation:Nein