Effect of supplementary cementitious materials on carbonation of cement pastes

Supplementary cementitious materials (SCM) are increasingly used in concrete for economical and environmental reasons. However, the durability of reinforced concretes against, example, corrosion induced by carbonation varies. Here, phase assemblage various cement pastes with/without SCM (slag, fly ash metakaolin), carbonated accelerated conditions (1.5% CO2 65% RH) or not, has been investigated technics (XRD, TGA/DTA 29Si as well 27Al nuclear magnetic resonance spectroscopy) compared. Results show that, after carbonation, anhydrous phases less decalcified than hydrated phases. In with slag, most calcium remains non-hydrated part slag. contrast, C-A,S-H is deeply modified results a coupling between aluminate during carbonation. all materials, these tend to become an aluminosilicate gel, very amorphous/disordered phase, containing water original hydrates.