Early mechanical properties and microstructural evolution of slag/metakaolin-based geopolymers exposed to karst water

As a type of corrosive mixed solution, karst water contains not only chloride and sulfate ions, but also a significant amount of bicarbonate ions. The early mechanical properties and microstructure of a metakaolin-based geopolymer and metakaolin/slag geopolymers (with 20 and 40 wt% slag replacing th...

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Bibliographic Details
Published in:Cement & concrete composites 2019-05, Vol.99, p.140-150
Main Authors: Xiang, Jichun, Liu, Leping, He, Yan, Zhang, Ning, Cui, Xuemin
Format: Article
Language:English
Subjects:
Geopolymer
Karst water corrosion
Microstructure
Pore structure
Slag
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Summary:As a type of corrosive mixed solution, karst water contains not only chloride and sulfate ions, but also a significant amount of bicarbonate ions. The early mechanical properties and microstructure of a metakaolin-based geopolymer and metakaolin/slag geopolymers (with 20 and 40 wt% slag replacing the metakaolin) immersed in karst water were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Barrett-Joyner-Halenda (BJH) analysis, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The results showed that a reduction in mechanical strengths associated with variations in the pore size, excess of alkalis (Na2O), decalcification of C-S-H, and calcium carbonate precipitation occurred after immersion in karst water. Furthermore, the geopolymers with the addition of less slag had a greater ability to resist corrosion by karst water. This is related to the formation of calcium carbonate in the calcium-rich geopolymer, along with the excess of alkali (Na+) for activated slag led to dissolve to the karst water.
ISSN:0958-9465
1873-393X
DOI:10.1016/j.cemconcomp.2019.03.009