Impact of carbonation on the durability of cementitious materials: water transport properties characterization

摘要

Within the context of long-lived intermediate level radioactive waste geological disposal,reinforced concrete would be used. In service life conditions,the concrete structures would be subjected to drying and carbonation. Carbonation relates to the reaction between carbon dioxide (CO_2) and the main hydrates of the cement paste (portlandite and C-S-H). Beyond the fall of the pore solution pH,indicative of steel depassivation,carbonation induces mineralogical and microstructural changes (due to portlandite and C-S-H dissolution and calcium carbonate precipitation). This results in the modification of the transport properties,which can impact the structure durability. Because concrete durability depends on water transport,this study focuses on the influence of carbonation on water transport properties. In fact,the transport properties of sound materials are known but they still remain to be assessed for carbonated ones. An experimental program has been designed to investigate the transport properties in carbonated materials. Four hardened cement pastes,differing in mineralogy,are carbonated in an accelerated carbonation device (in controlled environmental conditions) at CO_2 partial pressure of about 3%. Once fully carbonated,all the data needed to describe water transport,using a simplified approach,will be evaluated.