Techno Press
Techno Press

Computers and Concrete   Volume 19, Number 1, January 2017, pages 019-31
DOI: http://dx.doi.org/10.12989/cac.2017.19.1.019
 
Numerical investigation on gypsum and ettringite formation in cement pastes subjected to sulfate attack
Xiao-Bao Zuo, Jia-Lin Wang, Wei Sun, Hua Li and Guang-Ji Yin

 
Abstract     [Full Text]
    This paper uses modelling and experiment to perform a quantitative analysis for the gypsum and ettringite formations in cement pastes subjected to sulfate attack. Firstly, based on Fick\'s law and chemical reaction kinetics, a diffusion model of sulfate ions in cement pastes is proposed, and then the model of the gypsum and ettringite formations is established to analyze its contents in cement pastes with corrosion time. Secondly, the corrosion experiment of the specimens with cement pastes immersed into 2.5%, 5.0% and 10.0% Na2SO4 solutions are carried out, and by using XRD-Rietveld method, the phases of powder samples from the specimens are quantitatively analyzed to obtain the contents of gypsum and ettringite in different surface depth, solution concentration and corrosion time. Finally, the contents of gypsum and ettringite calculated by the models are compared with the results from the XRD experiments, and then the effects of surface depth, corrosion time and solution concentration on the gypsum and ettringite formations in cement pastes are discussed.
 
Key Words
    model; XRD-Rietveld analysis; gypsum; ettringite; cement pastes; sulfate attack
 
Address
Xiao-Bao Zuo, Jia-Lin Wang, Guang-Ji Yin: Department of Civil Engineering, Nanjing University of Science & Technology, Nanjing 210094, China
Wei Sun, Hua Li: Jiangsu Key Laboratory of Construction Materials, Southeast University, Nanjing 211189, China
 

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