Seminar – Philippe Turcry – How to understand carbonation in concrete

Abstract :

Carbonation of concrete is a reactive transfer of CO2 within the porous matrix of the material. After dissolving in the interstitial water, the CO2 reacts with the calcium ions provided by the cement hydrates to produce calcium carbonate, a very stable mineral phase. Although this phenomenon is well known, for many years it was studied, as shown by the literature review published in 1958 by Verbeck (1), it remains a topical research subject. Three factors may explain this consistency. Firstly, carbonation is a slow phenomenon, sometimes difficult to explore in the laboratory. Developments in measurement techniques are always providing new answers/questions. Secondly, the knowledge base was established for Portland cements with a high clinker content. After the emergence of new binders with reduced environmental impact over the last decade, it is necessary to update the data and even rethink the investigation methods. Lastly, carbonation can lead to corrosion of steel reinforcement, so it has mainly been considered in the context of the durability of reinforced concrete. However, “carbonation” literally means the mineralisation of CO2. A concrete element undergoing carbonation can be seen as a carbon sink. Against this backdrop, LaSIE (La Rochelle University), develop Over the last twenty years various approaches to understanding this reactive transfer, from accelerated testing to modelling and methods for studying the driving forces behind the phenomenon (gas diffusion, chemical reactivity). The objective of this seminar is to present and to analyze these different approaches, illustrated by a number of applications (carbonation of ‘ecoconcrete’, CO2 capture by recycled concrete aggregates…).

(1) G Verbeck. Carbonation of Hydrated Portland Cement, pages 17–36. ASTM International, West Conshohocken, PA, 01 1958.