2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference

Numerical model of the chloride transport by capillarity effects in cement materials

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Dr. Thomas Sanchez, Laval University (Presenter)
David Conciatori
Dr. Francine Laferrière

Reinforced concrete infrastructure subjected to wet-dry cycles is deteriorating at an accelerated rate. The transport of chloride ions, responsible for the corrosion of the reinforcements in these materials, is not only due to diffusion but also to the effects of water transport and capillarity. These two last phenomena are currently very poorly modelled. This work therefore aims to create a numerical model of multi-species and reactive transport of chlorinated ions by capillarity in a cementitious material. The main difficulty encountered in measuring capillary suction is the great complexity of obtaining experimental data. Indeed, a capillary test only makes it possible to obtain the concentration of chloride that has penetrated after a certain time. It is then necessary to carry out several of them under the same experimental conditions to obtain an evolution of the penetration of chloride ions. This study is based on innovative experimental work recently carried out (Conciatori et al., 2010): capillary tests with a chloride sensor inserted inside the cementitious matrix to measure the evolution of chloride concentration over time at a given penetration depth. During this study, simulations with the TransChlor prediction software had been carried out but did not allow to accurately simulate the phenomena involved by the experimental curve. One possible explanation is that the software used is uni-species and does not consider chemical reactions in a phenomenological way.

In the proposed article, we thus created a numerical model under the PhreeqC multi-species reactive transport software capable of modelling chloride transport during a capillarity test by a Reactive, Advective and Dispersive law. The model considers the diffusion of chlorinated ions and water transport by capillarity, as well as the chemical reactions that occur between the ions and the cementitious matrix in a phenomenological way. In larger perspective, this study let to improve knowledge in concrete durability structures in severe environmental condition and the numerical model that can be created to predict their life service to better maintenance.

Conciatori, D., Laferrière, F., Brühwiler, E., 2010. Comprehensive modeling of chloride ion and water ingress into concrete considering thermal and carbonation state for real climate. Cem. Concr. Res. 40, 109–118. https://doi.org/10/bd9q4n