Carbonation Rate of Alkali-Activated Concretes

Effects of Compositional Parameters and Carbonation Conditions

Book chapter (2023)

Authors

Gregor J.G. Gluth Federal Institute for Materials Research and Testing Berlin
Xinyuan Ke University of Bath
Anya Vollpracht Rheinisch-Westfälische Technische Hochschule
Lia Weiler Rheinisch-Westfälische Technische Hochschule
Susan A. Bernal University of Leeds
Martin Cyr Université de Toulouse
Katja Dombrowski-Daube University of Technology Bergakademie Freiberg
Dan Geddes University of Sheffield
Marija Nedeljković Materials and Environment - CEG
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Research Group
Materials and Environment (CEG) (TU Delft)
Copyright: © 2023 Gregor J.G. Gluth, Xinyuan Ke, Anya Vollpracht, Lia Weiler, Susan A. Bernal, Martin Cyr, Katja Dombrowski-Daube, Dan Geddes, Marija Nedeljković, More Authors
DOI
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https://doi.org/10.1007/978-3-031-33187-9_94
Durability Pore structure Carbonation Alkali-activated materials Accelerated testing
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Published Date

2023

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Materials- Mechanics- Management & Design

Research Group

Materials and Environment

Abstract

The current ability to predict the carbonation resistance of alkali-activated materials (AAMs) is incomplete, partly because of widely varying AAM chemistries and variable testing conditions. To identify general correlations between mix design parameters and the carbonation rate of AAMs, RILEM TC 281-CCC Working Group 6 compiled and analysed carbonation data for alkali-activated concretes and mortars from the literature. For comparison purposes, data for blended Portland cement-based concretes with a high percentage of SCMs (≥66% of the binder) were also included in the database. The results show that the water/CaO ratio is not a reliable indicator of the carbonation rate of AAMs. A better indicator of the carbonation rate of AAMs under conditions approximating natural carbonation is their water/(CaO + MgOeq + Na2Oeq + K2Oeq) ratio, where the index ‘eq’ indicates an equivalent amount based on molar masses. This finding can be explained by the CO2 binding capacity of alkaline-earth and alkali metal ions; the obtained correlation also indicates an influence of the space-filling capability of the binding phases of AAMs, as for conventional cements. However, this ratio can serve only as an approximate indicator of carbonation resistance, as other parameters also affect the carbonation resistance of alkali-activated concretes. In addition, the analysis of the dataset revealed peculiarities of accelerated tests using elevated CO2 concentrations for low-Ca AAMs, indicating that even at the relatively modest concentration of 1% CO2, accelerated testing may lead to inaccurate predictions of their carbonation resistance under natural exposure conditions.