Strategies for control and mitigation of efflorescence in metakaolin-based geopolymers

Efflorescence can be harmful to material performance as a consequence of microstructural changes due to leaching and carbonation of alkalis. This article identifies mechanisms of efflorescence in metakaolin-based geopolymers, and approaches to reduce free/mobile alkali cations and pore network conne...

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Bibliographic Details
Published in:Cement and concrete research 2021-06, Vol.144, p.106431, Article 106431
Main Authors: Longhi, Márlon A., Zhang, Zuhua, Walkley, Brant, Rodríguez, Erich D., Kirchheim, Ana Paula
Format: Article
Language:English
Subjects:
Admixtures
Alkali leaching
Aluminous cements
Aluminum
Blast furnace slags
Calcium aluminate
Calcium aluminum silicates
Carbonation
Cations
Dispersion
Efflorescence
Geopolymers
Leaching
Mass transport
Metakaolin
Performance enhancement
Silica fume
Silicates
Silicon dioxide
Silicone resins
Synthesis parameters
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Summary:Efflorescence can be harmful to material performance as a consequence of microstructural changes due to leaching and carbonation of alkalis. This article identifies mechanisms of efflorescence in metakaolin-based geopolymers, and approaches to reduce free/mobile alkali cations and pore network connectivity, and hence reduce efflorescence. Mechanical, mass transport and microstructural properties are assessed in metakaolin-based geopolymer cements produced using different alkali concentrations in the alkali activator and substitution/addition of blast furnace slag, silica fume, calcium aluminate cement, silicone oil and a dispersive admixture. The most effective strategy to reduce efflorescence results from increasing Si/Al in the geopolymer gel by addition of soluble silicate, silica fume or silicone oil. Addition of calcium aluminate cement or a dispersive admixture also reduce efflorescence, but are less effective. These results confirm that efflorescence may be reduced by controlling the amount of soluble silicates and reducing free alkali cations in geopolymers, providing enhanced performance and durability.
ISSN:0008-8846
1873-3948
DOI:10.1016/j.cemconres.2021.106431