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Influence of rheology modifying admixtures on early hydration of cementitious suspensions

  • The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this paper presents experimental results about the influence of delayed addition of PCEs on the Hydration of cement and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3A pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less Retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that there is less retardation the later the addition of SP. Furthermore, the PCE alter the hydration of C3A whenThe presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this paper presents experimental results about the influence of delayed addition of PCEs on the Hydration of cement and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3A pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less Retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that 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. XRD results showed that more C3A is dissolved in the presence of PCE. Also, the gypsum depletion occurs earlier in the presence of PCE and even faster with delayed addition. Without PCE AFm starts to form just after the gypsum depletion. However, in the presence of PCE AFm already starts to form at the beginning of the hydration. Due to the faster gypsum depletion in the presence of PCE, also the transformation from ettringite into AFm begins earlier, but takes longer as without SP.zeige mehrzeige weniger

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Metadaten
Autoren/innen:Claudia Crasselt, Wolfram Schmidt, Heinz Sturm
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):PAPERS AND POSTERS PROCEEDINGS 15th International Congress on the Chemistry of Cement
Jahr der Erstveröffentlichung:2019
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
Erste Seite:1
Letzte Seite:8
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:C3A; Cement; Delayed addition; Early hydration; Polycarboxylate ether (PCE)
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Materialien und Stoffe
Analytical Sciences
Analytical Sciences / Oberflächen- und Grenzflächenanalytik
Veranstaltung:15th International Congress on the Chemistry of Cement
Veranstaltungsort:Prague, Czech Republic
Beginndatum der Veranstaltung:16.09.2019
Enddatum der Veranstaltung:20.09.2019
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:25.09.2019
Referierte Publikation:Nein