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

The hydration behaviour of Ca3Al2O6, Ca12Al14O33 and CaAl2O4 with added amorphous silica at 40, 65 and 90 degrees C has been studied for periods ranging from I to 31 days. In hydrated samples crystalline phases like katoite (Ca3Al2(SiO4)(3-x)(OH)(4x)) and gibbsite, AI(OH)3, were identified, likewise amorphous phases like AI(OH),, calcium silicate hydrates, C S-H, and calcium alummosilicate 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. (c) 2006 Elsevier Inc. All rights reserved.