Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives
Keywords: 
Metakaolin
Nanosilica
Zeta potential
Air lime mortar
Pozzolan
Admixture
Polycarboxylate
Flowability
Issue Date: 
30-Dec-2014
Publisher: 
Elsevier
ISSN: 
0950-0618
Citation: 
Navarro-Blasco I, Perez-Nicolas M, Fernandez JM, Duran A, Sirera R, Alvarez JI. Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives. Constr Build Mater 2014;73:1-12.
Abstract
Two polycarboxylate ether copolymers were assessed as superplasticizers (SPs) for hydrated lime pastes modified with two reactive compounds, nanosilica (NS) and ceramic metakaolin (MK). Characterization of the molecular structure of the SPs by Size Exclusion Chromatography, XRD, FTIR and MALDI-TOF (Matrix Assisted Laser Desorption Ionization Time-of-Flight) mass spectrometry was performed. The structures of the polymers were seen to be star- and worm-like shapes. A close relationship was found between the molecular architecture and the flowability of the pastes, being the star-shaped plasticizer the most efficient. Zeta potential assessment allowed us to elucidate a steric hindrance as the main action mechanism for these polymers. The large specific surface area of nanosilica led to a large SPs consumption as compared with metakaolin with lower surface area. However, SPs in MK-lime samples were attached favourably on the C-S-H and aluminate hydrates, so that the dispersing action was greater with respect to NS-lime suspensions.

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