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Investigations on Stability of Polycarboxylate Superplasticizers in Alkaline Activators for Geopolymer Binders

  • Calcined clays are interesting starting materials to be used as SCMs (supplementary cementitious materials) in cements or to be converted to geopolymers by activation with a high alkaline activator. The adjustment of the properties in the fresh state, especially regarding the consistency of these binders, is almost exclusively achieved by the addition of water, since commercially availableCalcined clays are interesting starting materials to be used as SCMs (supplementary cementitious materials) in cements or to be converted to geopolymers by activation with a high alkaline activator. The adjustment of the properties in the fresh state, especially regarding the consistency of these binders, is almost exclusively achieved by the addition of water, since commercially available superplasticizers seem to be ineffective in low-calcium geopolymer systems. The aim of this study was a systematic investigation of various PCE (polycarboxylate ester/ether) superplasticizers (methacrylate ester PCE: MPEG, isoprenol ether PCE: IPEG, methallyl ether PCE: HPEG) with respect to their stability in different alkaline activators (NaOH, KOH, sodium and potassium silicate solutions). The effectiveness of superplasticizers (SPs) in low-calcium geopolymer binders was verified by rheological tests. Size exclusion chromatography was used to investigate if structural degradation of the superplasticizers occurs. The investigated PCE superplasticizers showed a thickening effect in the low-calcium geopolymer system. Depending on the alkalinity of the activator solution, a degradation process was detected for all the PCEs investigated. The side chains of the PCEs are cleaved off the backbone by basic ester and ether hydrolysis. The highest degree of degradation was found in sodium and potassium silicate solutions. In alkaline hydroxide solutions, the degradation process increases with increasing alkalinity.show moreshow less

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Metadaten
Document Type:Article
Author:Dr.-Ing. Stephan PartschefeldORCiDGND, Adrian TutalORCiD, Thomas Halmanseder, Dr.-Ing. Jens SchneiderORCiD, Prof. Dr.-Ing. Andrea OsburgORCiDGND
DOI (Cite-Link):https://doi.org/10.3390/ma16155369Cite-Link
URN (Cite-Link):https://nbn-resolving.org/urn:nbn:de:gbv:wim2-20231026-64809Cite-Link
URL:https://www.mdpi.com/1996-1944/16/15/5369
Parent Title (English):Materials
Publisher:MDPI
Place of publication:Basel
Language:English
Date of Publication (online):2023/10/23
Date of first Publication:2023/07/31
Release Date:2023/10/26
Publishing Institution:Bauhaus-Universität Weimar
Institutes and partner institutions:Fakultät Bauingenieurwesen / Professur Bauchemie und Polymere Werkstoffe
Volume:2023
Issue:Volume 16, issue 15, article 5369
Pagenumber:14
First Page:1
Last Page:14
Tag:OA-Publikationsfonds2023
metakaoline; polycarboxylate ether; superplasticizer
GND Keyword:Geopolymere; Verflüssigung
Dewey Decimal Classification:500 Naturwissenschaften und Mathematik / 540 Chemie
BKL-Classification:51 Werkstoffkunde / 51.60 Keramische Werkstoffe, Hartstoffe
Open Access Publikationsfonds:Open-Access-Publikationsfonds 2023
Licence (German):License Logo Creative Commons 4.0 - Namensnennung (CC BY 4.0)