Modelling of concrete carbonation based on coupled mass transport and chemical reactions

Author(s): M. Thiery, G. Villain, V. Baroghel-Bouny, P. Dangla
Paper category: Workshop
Book title: International RILEM Workshop on Performance Based Evaluation and Indicators for Concrete Durability
Editor(s): V. Baroghel-Bouny, C. Andrade, R. Torrent, K. Scrivener
ISBN: 978-2-912143-95-2
Pages: 135 - 144
Total Pages: 10
Language: English

The physicochemical processes of carbonation of cement based materials are modelled. They include the diffusion of carbon dioxide CO₂ in the gas phase, its dissolution in the aqueous film of the pores, the transport of water by Darcean advection, and the ions diffusion in the pore water solution. Moreover, the model takes into account the chemical reactions of dissolution of hydrates, and of precipitation of calcium carbonates. Each chemical reaction is either at equilibrium or is characterised by a kinetic law. The reduction of porosity and the release of water from the hydrates during carbonation are also described.

The durability indicators porosity, initial Ca(OH)₂ content, and water permeability are introduced as major input data. Complementary parameters are also used: Ca(OH)₂ crystal size, C-S-H content, and capillary pressure curve. The main numerical outputs are the depth of carbonation, as well as the residual Ca(OH)₂, newly formed CaCO₃ content and pH profiles. The reliability of the model is verified by comparing the predictions with results of accelerated carbonation tests conducted on a cement paste and several concretes. The effects of some parameters like durability indicators on the carbonation propagation are also discussed.

Online publication: 2007
Publication Type: full_text
Public price (Euros): 0.00

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