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Carbonation mechanism of different kinds of C-S-H: Rate and products

Author(s): Bei Wu, Guang Ye
Paper category: Proceedings
Book title: Proceedings of the International RILEM Conference
Materials, Systems and Structures in Civil Engineering 2016
Segment on Concrete with Supplementary Cementitious Materials
Editor(s): Ole M. Jensen, Konstantin Kovler and Nele De Belie
e-ISBN: 978-2-35158-179-7
Publisher: RILEM Publications SARL
Publication year: 2016
Pages: 276-285
Total Pages: 10
Language : English

Abstract: During the carbonation of cement paste blended with supplementary cementitious materials, the C-S-H with different Ca/Si ratios, formed from the hydration and pozzolanic reactions, are the major calcium-bearing phases which react with CO2. Therefore, it’s important to study the carbonation mechanism of different C-S-H phases. In this paper, the pure C-S-H phases (Ca/Si ratio: 0.66 to 2.0) were synthesized and used for the accelerated carbonation test. Synthesized C-S-H phases with different Ca/Si ratio were identified by X-ray diffraction and 29Si nuclear magnetic resonance. The carbonation rate and products of different C-S-H phases are also determined. The results show that pure C-S-H phases with different Ca/Si ratio (lower than 1.40) can be synthesized in the lab. The structure of synthesized C-S-H is similar to the C-S-H(I) reported by Taylor. The mean chain length of the C-S-H decreases dramatically when the Ca/Si ratio increases from 0.66 to 1.40, then it keeps no change. The portlandite appears in the products when the designed Ca/Si ratio is over 1.40. The C-S-H with lower Ca/Si ratio is decomposed faster than that with a higher Ca/Si ratio. All the C-S-H phases are fully decomposed to CaCO3 and silica gel after 3 days’ accelerated carbonation.

Online publication : 2016
Publication type : full_text
Public price (Euros) : 0.00

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