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Alkalinity and Its Consequences for the Performance of Steel-Reinforced Geopolymer Materials

Koenig, Andreas; Mahmoud, Hitham; Baehre, Oliver; Dehn, Frank 1
1 Institut für Massivbau und Baustofftechnik (IMB), Karlsruher Institut für Technologie (KIT)


This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated fly ashes with ten percentage mass (wt%) of blast furnace slag (AAFAS)-based materials (geopolymer–GP). The pH analysis of eluates indicates a remarkable decrease of alkalinity in AAFA and AAFAS in the first hours of the geopolymerization process. Phenolphthalein solution and pore solution tests on concretes also show a sharp decrease of alkalinity with increased Ca content in the binder due to carbonation. Micro X-ray computer tomography (µXCT) and electrochemical techniques indicate that the changed pH in the GP systems was accompanied by a decrease in the corrosion rates of steel reinforcement when compared to ordinary Portland cement (OPC) systems. In contrast to calcite and vaterite, which were detected in OPC and AAFAS after a carbonation process, only sodium carbonate natron was determined at lower levels in AAFA by X-ray diffraction (XRD).

Verlagsausgabe §
DOI: 10.5445/IR/1000121094
Veröffentlicht am 08.07.2020
DOI: 10.3390/molecules25102359
Zitationen: 1
Zitationen: 6
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Massivbau und Baustofftechnik (IMB)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 1420-3049
KITopen-ID: 1000121094
Erschienen in Molecules
Verlag MDPI
Band 25
Heft 10
Seiten Art. Nr.: 2359
Vorab online veröffentlicht am 19.05.2020
Schlagwörter geopolymer concrete, alkalinity, micro X-ray computer tomography (μXCT), steel reinforcement corrosion
Nachgewiesen in Scopus
Web of Science
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