Carbonation Resistance of Alkali-Activated Slag Under Natural and Accelerated Conditions

Carbonation Resistance of Alkali-Activated Slag Under Natural and Accelerated Conditions In this paper, carbonation resistance of alkali-activated slag (AAS) pastes exposed to natural and accelerated conditions up to 1 year was investigated. Two aspects of carbonation mechanism were evaluated. The first was the potential carbonation of the main binding phases in finely powdered AAS pastes. The second was the reactivity and diffusivity of CO2 within the bulk AAS paste. From Fourier transform infrared spectroscopy and thermogravimetric analysis coupled with mass spectroscopy time-series measurements, it was found that powdered AAS was largely carbonated within 28 days with a CO2 uptake of 14 wt%. The main carbonation products were calcium carbonates. Nevertheless, the bulk paste samples were highly resistant to carbonation, regardless of the exposure conditions. The findings showed that the pH value (initial pH > 12) and strength of the samples did not decrease under accelerated carbonation compared to those of the samples exposed under natural conditions. The mineralogy of the samples in these two carbonation exposures did not alter either, except for outdoor conditions. The gel pores were dominant in the pastes (pore size in range of 2–15 nm). The dense microstructure was the main barrier for CO2 to diffuse and further react with binding phases. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Sustainable Metallurgy Springer Journals

Carbonation Resistance of Alkali-Activated Slag Under Natural and Accelerated Conditions

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Publisher
Springer International Publishing
Copyright
Copyright © 2018 by The Author(s)
Subject
Environment; Sustainable Development; Metallic Materials
ISSN
2199-3823
eISSN
2199-3831
D.O.I.
10.1007/s40831-018-0166-4
Publisher site
See Article on Publisher Site

Abstract

In this paper, carbonation resistance of alkali-activated slag (AAS) pastes exposed to natural and accelerated conditions up to 1 year was investigated. Two aspects of carbonation mechanism were evaluated. The first was the potential carbonation of the main binding phases in finely powdered AAS pastes. The second was the reactivity and diffusivity of CO2 within the bulk AAS paste. From Fourier transform infrared spectroscopy and thermogravimetric analysis coupled with mass spectroscopy time-series measurements, it was found that powdered AAS was largely carbonated within 28 days with a CO2 uptake of 14 wt%. The main carbonation products were calcium carbonates. Nevertheless, the bulk paste samples were highly resistant to carbonation, regardless of the exposure conditions. The findings showed that the pH value (initial pH > 12) and strength of the samples did not decrease under accelerated carbonation compared to those of the samples exposed under natural conditions. The mineralogy of the samples in these two carbonation exposures did not alter either, except for outdoor conditions. The gel pores were dominant in the pastes (pore size in range of 2–15 nm). The dense microstructure was the main barrier for CO2 to diffuse and further react with binding phases.

Journal

Journal of Sustainable MetallurgySpringer Journals

Published: Feb 16, 2018

References

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