The most widely identified degradation process suffered by calcium aluminate cement (CAC) is the so-called conversion of hexagonal
calcium aluminate hydrate to cubic form. This conversion is usually followed by an increase in porosity determined by the
different densities of these hydrates and the subsequent loss of strength. Mixes of calcium aluminate cement (CAC) and silica
fume (SF) or fly ash (FA) represent an interesting alternative for the stabilization of CAC hydrates, which might be attributed
to a microstructure based mainly on aluminosilicates. This paper deals with the microstructure of cement pastes fabricated
with mixtures CAC-SF and CAC-FA and its evolution over time. Thermal analysis (DTA/TG), X-ray diffraction (XRD) and mid-infrared
spectroscopy (FTIR) have been used to assess the microstructure of these formulations.