New test method for assessing the carbonation front in alkali-activated fly ash/slag Pastes

M. Nedeljkovic, Y. Zuo, Kamel Arbi, G. Ye

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

Abstract

Carbonation of the pore solution in alkali-activated materials (AAMs) produces alkali and/or alkali-earth carbonates. When the carbonate solubility in the water is very high (case of the most alkali carbonates), it is very hard to determine the carbonation depth in AAMs with the phenolphthalein indicator frequently used in Ordinary Portland Cement (OPC)-based materials. Carbonation gradually decreases the alkalinity of the pore solution, while the color after spraying phenolphthalein changes from colorless to pink when pH< 13 and changes back to colorless when pH< 8.2. The color change with phenolphthalein indicator may still exist in the less alkaline areas where carbonation may have already occurred. Therefore, using the indicator test is likely to underestimate the depth to which carbonation reaction has occurred in AAMs and more complete assessment is required. This study investigates the carbonation front in alkali-activated fly ash (FA) and blast furnace slag (BFS) pastes in natural laboratory conditions. Monitoring carbonation front in the samples after one year of exposure has been carried out under polarized light microscope (PLM), and environmental scanning electron microscope (ESEM). The carbonation products were sharply distinguished from the other constituents of the paste, by their crystallographic and optical characteristics under PLM, and characterized by X-Ray diffraction (XRD).

Original languageEnglish
Title of host publicationNon-Traditional Cement and Concrete VI
Subtitle of host publicationProceedings of the International Conference
EditorsVlastimil Bilek, Hans Simonova
Pages28-29
Number of pages2
Publication statusPublished - 2018
Event6th International Conference Non-Traditional Cement and Concrete, 2017 - Brno, Czech Republic
Duration: 19 Jun 201722 Jun 2017
Conference number: 6

Conference

Conference6th International Conference Non-Traditional Cement and Concrete, 2017
CountryCzech Republic
CityBrno
Period19/06/1722/06/17

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