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The effect of superplasticizers on rheology and early hydration kinetics of rice husk ash-blended cementitious systems

  • Superplasticizers (SPs) have been employed in concrete technology for decades to improve the workability of concrete in its fresh state. The addition of SPs in cement-based systems affects the early properties. Although the interaction of the cement particles with various SPs has been extensively researched, there still exists limited research on the interaction of SPs with supplementary cementitious materials such as rice husk ash (RHA). This paper investigates the rheological properties and early hydration kinetics of RHA-blended systems with three types of SPs, a polycarboxylate ether (PCE) and two lignosulphonates (LS-acc and LS-ret). In rheological properties, the addition of SP causes an initial improvement of workability as the yield stress is significantly reduced. The pastes with PCE and LS-acc show a slight increase of yield stress over time whereas pastes with LS-ret tend to lower the yield stress slightly over time, further improving the workability. Without SP, pastes withSuperplasticizers (SPs) have been employed in concrete technology for decades to improve the workability of concrete in its fresh state. The addition of SPs in cement-based systems affects the early properties. Although the interaction of the cement particles with various SPs has been extensively researched, there still exists limited research on the interaction of SPs with supplementary cementitious materials such as rice husk ash (RHA). This paper investigates the rheological properties and early hydration kinetics of RHA-blended systems with three types of SPs, a polycarboxylate ether (PCE) and two lignosulphonates (LS-acc and LS-ret). In rheological properties, the addition of SP causes an initial improvement of workability as the yield stress is significantly reduced. The pastes with PCE and LS-acc show a slight increase of yield stress over time whereas pastes with LS-ret tend to lower the yield stress slightly over time, further improving the workability. Without SP, pastes with RHA show a lower yield stress but an increase in plastic viscosity as cement is further replaced with RHA. The addition of the LS SPs is observed to lower the plastic viscosity but remains constant with further replacement of cement with RHA. This indicates that LS SPs further adsorbs on RHA particles and hydration products produced causing dispersion of the particles within the system. In early hydration kinetics, pastes with PCE retard hydration and the degree of retardation is further increased with LS SPs. In the presence of RHA, the retardation of LS SP systems is significantly reduced. The pastes with PCE show more ettringite in the SEM micrographs, but is observed to be shorter needles. This indicates an initial good workability for PCE. However, C-S-H and CH were observed to be low in quantity, whereby the pastes with LS show more nucleation sites for C-S-H and CH. The ettringite needles in the LS systems were similar in quantity and more elongated in some cases but not abundant as in the PCE systems.zeige mehrzeige weniger

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Autor*innen:Nsesheye Susan PriebeORCiD, Wolfram SchmidtORCiD, Berta Mota, Sarah Leinitz, Hans-Carsten KühneORCiD, Andreas Rogge
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Construction and Building Materials
Jahr der Erstveröffentlichung:2017
Verlag:Elsevier Ltd.
Jahrgang/Band:150
Erste Seite:511
Letzte Seite:519
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:CO2 reduction; Cement; Hydration; Plastic viscosity; Rheology; Rice husk ash; Slump flow; Superplasticizers; Supplementary cementitious materials; Yield stress
DOI:10.1016/j.conbuildmat.2017.05.197
URL:http://www.sciencedirect.com/science/article/pii/S0950061817310978?via%3Dihub
ISSN:0950-0618
ISSN:1879-0526
Bemerkung:
Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. -  Birth name of Priebe, Nsesheye Susan: Msinjili, N. S.
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:18.07.2017
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:31.08.2017
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