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Formation of Geopolymers Using Sodium Silicate Solution and Aluminum Orthophosphate

  • This paper reports the formation and structure of fast setting geopolymers activated by using three sodium silicate solutions with different modules (1.6, 2.0 and 2.4) and a berlinite-type aluminum orthophosphate. By varying the concentration of the aluminum orthophosphate, different Si/Al-ratios were established (6, 3 and 2). Reaction kinetics of binders were determined by isothermal calorimetricThis paper reports the formation and structure of fast setting geopolymers activated by using three sodium silicate solutions with different modules (1.6, 2.0 and 2.4) and a berlinite-type aluminum orthophosphate. By varying the concentration of the aluminum orthophosphate, different Si/Al-ratios were established (6, 3 and 2). Reaction kinetics of binders were determined by isothermal calorimetric measurements at 20 °C. X-ray diffraction analysis as well as nuclear magnetic resonance (NMR) measurements were performed on binders to determine differences in structure by varying the alkalinity of the sodium silicate solutions and the Si/Al-ratio. The calorimetric results indicated that the higher the alkalinity of the sodium silicate solution, the higher the solubility and degree of conversion of the aluminum orthophosphate. The results of X-ray diffraction and Rietveldt analysis, as well as the NMR measurements, confirmed the assumption of the calorimetric experiments that first the aluminum orthophosphate was dissolved and then a polycondensation to an amorphous aluminosilicate network occurred. The different amounts of amorphous phases formed as a function of the alkalinity of the sodium silicate solution, indicate that tetrahydroxoaluminate species were formed during the dissolution of the aluminum orthophosphate, which reduce the pH value. This led to no further dissolution of the aluminum orthophosphate, which remained unreacted.show moreshow less

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Metadaten
Document Type:Article
Author:Dipl.-Ing. Stephan Partschefeld, Dr. rer. nat. Torben WiegandGND, Dr.-Ing. Frank BellmannORCiD, Prof. Dr.-Ing. Dipl.-Chem. Andrea OsburgORCiDGND
DOI (Cite-Link):https://doi.org/10.3390/ma13184202Cite-Link
URN (Cite-Link):https://nbn-resolving.org/urn:nbn:de:gbv:wim2-20210122-43378Cite-Link
URL:https://www.mdpi.com/1996-1944/13/18/4202
Parent Title (English):Materials
Publisher:MDPI
Place of publication:Basel
Language:English
Date of Publication (online):2021/01/20
Date of first Publication:2020/09/21
Release Date:2021/01/22
Publishing Institution:Bauhaus-Universität Weimar
Institutes and partner institutions:Fakultät Bauingenieurwesen / Professur Bauchemie und Polymere Werkstoffe
Volume:2020
Issue:Volume 13, issue 18, article 4202
Pagenumber:16
First Page:1
Last Page:16
Tag:alumosilicate; berlinite; geopolymer; sodium silicate solution
GND Keyword:Geopolymere
Dewey Decimal Classification:600 Technik, Medizin, angewandte Wissenschaften / 660 Chemische Verfahrenstechnik / 668 Technik anderer organischer Produkte
BKL-Classification:51 Werkstoffkunde / 51.60 Keramische Werkstoffe, Hartstoffe
Open Access Publikationsfonds:Open-Access-Publikationsfonds 2020
Licence (German):License Logo Creative Commons 4.0 - Namensnennung (CC BY 4.0)