X-ray Total Scattering Study of Phases Formed from Cement Phases Carbonation

Carbonation in cement binders has to be thoroughly understood because it affects phase assemblage, binder microstructure and durability performance of concretes. This is still not the case as reaction products can crystalline, nanocrystalline amorphous. The characterisation last two types components are quite challenging. Here, carbonation reactions have been studied alite-, belite- ye’elimite-containing pastes, controlled conditions (3% CO2 RH = 65%). Pair distribution function (PDF) jointly with Rietveld thermal analyses applied prove that ettringite decomposed yield crystalline aragonite, bassanite nano-gibbsite without any formation amorphous calcium carbonate. particle size gibbsite under these was found larger (~5 nm) than coming from direct hydration ye’elimite anhydrite (~3 nm). Moreover, mixtures C-S-H gel portlandite, alite belite hydration, led three CaCO3 polymorphs (calcite, aragonite vaterite), silica In addition their PDF profiles, traces analysed discussed.