Normal and anomalous self-healing mechanism of crystalline calcium silicate hydrates

The origin of different stability of crystalline calcium silicate hydrates was investigated. The tobermorite crystal has been used as an analog of cement hydrate that is being mostly manufactured material on earth. Normal tobermorite is thermally unstable and transforms to amorphous at low pressure....

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Bibliographic Details
Published in:Cement and concrete research 2021-04, Vol.142 (C), p.106356, Article 106356
Main Authors: Dupuis, Romain, Moon, Juhyuk, Jeong, Yeonung, Taylor, Rae, Kang, Sung-Hoon, Manzano, Hegoi, Ayuela, Andrés, Monteiro, Paulo J.M., Dolado, Jorge S.
Format: Article
Language:English
Subjects:
Aluminum
Amorphous materials
Calcium ions
Calcium silicate hydrate
Calcium silicates
Cement hydrate
Chains
Crystal defects
Crystal structure
Crystallinity
High temperature
Low pressure
Molecular simulation
Self-healing mechanism
Structural stability
Tobermorite
X ray absorption
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Summary:The origin of different stability of crystalline calcium silicate hydrates was investigated. The tobermorite crystal has been used as an analog of cement hydrate that is being mostly manufactured material on earth. Normal tobermorite is thermally unstable and transforms to amorphous at low pressure. Meanwhile, anomalous tobermorite with high Al content does not significantly transform under high pressure or high temperature. Conducted X-ray absorption spectroscopy explains the weak stability of normal tobermorite which was originally hypothesized by the role of zeolitic Ca ions in the cavities of silicate chains. Atomic simulations reproduced the experimentally observed trend of pressure behavior once the ideal structures were modified to account for the Al content as well as the chain defects. The simulations also suggested that the stability of tobermorite under stress could be rationalized as a self-healing mechanism in which the structural instabilities were accommodated by a global sliding of the CaO layer.
ISSN:0008-8846
1873-3948
DOI:10.1016/j.cemconres.2021.106356