MODELLING OF TEMPERATURE IMPACTS ON CEMENT PASTE IN CLAYEY ENVIRONMENT CONSTRAINED BY FIELD EXPERIMENTS

Author(s): Philippines Lalan, Laurent De Windt, Alexandre Dauzères, Valéry Detilleux
Book Title: RILEM International Symposium on Concrete Modelling - CONMOD 2014
Editor: Kefei Li, Peiyu Yan and Rongwei Yang
ISBN: 978-2-35158-139-1
e-ISBN: 978-2-35158-140-7
Publisher: RILEM Publications SARL
Publication year: 2015
Pages: 335-342
Total Pages: 8
Language: English

Abstract: Cementitious materials will be used for the facility and waste containers in clayey deep geological disposal of radioactive wastes. Contrasting chemical properties of cement and clay induce strong perturbations of chemistry, microstructure and transport properties around their contact. Beside, temperature at the cement / clay interface could rise until 70°C during decades. IRSN has developed field experiments in the Tournemire URL to better assess material physico-chemical behaviour under such conditions. In modelling, temperature effect raises the issue of acquiring a relevant set of thermodynamic constants and activation energies for the diffusion of dissolved species and the kinetic rate of chemical reactions. A first set of experimental results corresponding to one year of in situ interactions has provided data to strongly constrain reactive transport modelling: i) decalcification (portlandite dissolution, decrease of the C/S ratio of C-S-H), carbonation in the cement paste, ii) precipitation of tobermorite and phillipsite (zeolite) at the interface on the argillite side, iii) kaolinite dissolution and illite precipitation inside the argillite. Simplified stability (phase) diagram and reactive transport modelling were performed with the code CHESS/HYTEC and the Thermoddem thermodynamic database. Modelling was in good agreement with experiment, but overestimated the degradation depth and zeolite precipitation occurred too far from the interface. Feedback of chemical modifications on transport properties may be quite sensitive to temperature and are under current experimental investigations.

Online publication: 2015
Publication Type: full_text
Public price (Euros): 0.00