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.…
Document Type: | Article |
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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): | Creative Commons 4.0 - Namensnennung (CC BY 4.0) |