Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 deg. C

The hydration behaviour of Ca3Al2O6, Ca12Al14O33 and CaAl2O4 with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca3Al2(SiO4)3-x (OH)4x ) and gibbsite, Al(OH)3, were identified, likewise amorphous phases like Al(OH) x , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca3Al2(SiO4)3-x (OH)4x (0≤3-x≤0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca3Al2(SiO4)3-x (OH)4x (0≤3-x≤0.334), was identified besides gibbsite, Al(OH)3, as a crystalline stable hydration products in Ca3Al2O6, Ca12Al14O33 and CaAl2O4 hydrated with added amorphous silica between 40 and 90 deg. C