Carbonation of model cement pastes: The mineralogical origin of microstructural changes and shrinkage

This study explored the reactive processes of atmospheric carbonation and consequences with respect to cementitious materials. Two model pastes were used: hydrated C3S (including C-S-H portlandite) a paste prepared by hydrating blend nanosilica only). The two carbonated under accelerated conditions in laboratory. resulting mineralogical assemblage was examined using X-ray diffraction, thermogravimetric analysis nuclear magnetic resonance. microstructural changes studied tomography porosimetry, their macroscopic impacts evaluated through gas diffusion shrinkage measurements. use allowed for evaluation change solid volume induced C-S-H. decalcification subsequent silica chain polymerisation found responsible (and potentially cracking). Finally, results highlight protective role portlandite: portlandite helped limiting then reducing cracking.