Long-term evolution of delayed ettringite and gypsum in Portland cement mortars under sulfate erosion

The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results sho...

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Bibliographic Details
Published in:Construction & building materials 2009-02, Vol.23 (2), p.812-816
Main Authors: Chen, Jian-kang, Jiang, Min-qiang
Format: Article
Language:English
Subjects:
Ettringite formation
Evaluation
Gypsum
Gypsum formation
Portland cement
Portland cement mortars
Properties
Sulfate pulping process
Sulfate sodium
Testing
XRD method
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Summary:The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results show that the magnitude of ettringite formation in sodium sulfate solution follows a three-stage process, namely, the ‘penetration period’, ‘enhance period of strength’, and ‘macro-crack period’. The cracking of concrete materials is mainly attributed to the effect of ettringite. The gypsum formations occurred in two stages, the ‘latent period’ and the ‘accelerated period’. The gypsum formation including ettringite formation was relative to the linear expansion of mortars to some extend. Both water-to-cement ratio and sulfate concentration play important roles in the evolution of ettringite and gypsum.
ISSN:0950-0618
1879-0526
DOI:10.1016/j.conbuildmat.2008.03.002