Modeling of calcium leaching from cement hydrates coupled with microstructure formation

Title: Modeling of calcium leaching from cement hydrates coupled with microstructure formation
Author(s): K. Nakarai, T. Ishida, K. Maekawa, T. Kishi
Paper category : conference
Book title: International RILEM Symposium on Concrete Modelling - ConMod '08
Editor(s): E. Schlangen and G. De Schutter
Print-ISBN: 978-2-35158-060-8
e-ISBN: 978-2-35158-076-9
Publisher: RILEM Publications SARL
Publication year: 2008
Pages: 385 - 382
Total Pages: -2
Nb references: 8
Language: English

Abstract: The applicability of concrete as a solidifying barrier for the geological disposal of radioactive waste is being studied in Japan. Radioactive waste contains materials with long half-lives, so the period of stability required in design is several tens of thousands of years.
Calcium leaching is one issue of crucial importance to be considered in the design and planning of such projects.
In this study, a computational system for predicting the long-term degradation of cement hydrates due to calcium leaching is presented. The leaching of calcium ions from hardened hydrates is simulated as the multi-phase equilibrium of calcium in solid and liquid phases and their transport is formulated on the basis of thermodynamics. The time-dependent properties of cement hydrates associated with hydration, microstructure development, moisture and chloride ion transports are evaluated by integrating calcium leaching and statistical models of chemo-physics. For developing the mature modeling of calcium leaching coupled with microstructure formation, the microstructure model was enhanced to take into account the influence of the temperature history and the content of calcium hydrates and C-S-H gel.
Through a series of comparisons with the experimental results, the proposed model showed reasonable predictions of microstructure formation and calcium leaching. The model further suggested that low water-to-cement concrete has a high resistance to leaching as self-curing takes place.

Online publication: 2009-06-15
Publication type : full_text
Public price (Euros): 0.00