Reference:  S. Kamali, M. Moranville, E. Garboczi, S. Prené, B. Gérard   submitted for publication in "International Conference on Fracture Mechanics of Concrete and Concrete Structures" (2003).
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Hydrate dissolution influence on the Young's modulus of cement pastes

S. Kamali & M. Moranville
LMT, ENS-Cachan, 61 avenue du Président Wilson, 94230 Cachan, France

E. Garboczi
National Institute of Standards and Technology, Gaithersburg, Maryland 20899 USA

S. Prené
EDF-R&D/Les Renardières, Ecuelles, F-77818 Moret sur Loing Cedex, France

B. Gérard
OXAND S.A., 36 bis, avenue Franklin Roosevelt, 77210 Avon, France

ABSTRACT:

Leaching of concrete by water may severely damage structures like radioactive waste depositories or water supply stations. This paper presents the influence of water leaching on the mechanical properties of cement pastes. The NIST microstructure model CEMHYD3D and elastic model ELAS3D were used to quantify the effect of the dissolution of cement hydrates like calcium hydroxide (CH), monosulphoaluminate (AFm) and ettringite (AFt), on the Young's modulus. The results clearly indicate the important impact of calcium hydroxide dissolution on the decrease of this parameter. Calcium hydroxide leaching can reduce the Young's modulus by more than 50 %, depending on the initial calcium hydroxide content. Different cement pastes were simulated to investigate the effect of two parameters: water to cement ratio and silica fume addition. An empirical equation relating the capillary porosity to the Young's modulus was developed.

Keywords: cement, hydrates, microstructure, leaching, dissolution, portlandite, monosulfoaluminate, ettringite, porosity, elastic moduli

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