Microstructural analysis of aerated cement pastes with fly ash, Metakaolin and Sepiolite additions

Products formation in aerated cement pastes, using aluminum powder as expansion agent, is studied in order to determine the effect of Metakaolin (MK) and Sepiolite (SP) addition as well as cement selection, in pore network. Products generated are related to cement hydration and chemical reactions involved in the aeration process. This is due to the batch materials and additions used in order to increase both, expansion rate and speed. XRD combined with DTA was used to characterize these products and their relation with pore network in the hardened foamed mortar, studied by SEM combined with EDX. As a conclusion, the presence of siliceous fly ashes (SFA) in ordinary Portland cement together with additions of MK or/and SP provides the largest expansion values beside a higher closed porosity of the foamed mortar. It is also stated that mixes with Metakaolin have better defined walls and almost closed cells that are important properties for thermal insulation materials and can be useful for ventilated double skin façade systems.