Carbonation of ternary building cementing materials

The carbonation processes of ettringite and calcium aluminate hydrates phases developed by hydration of calcium aluminate cement, fly ash and calcium sulphate ternary mixtures have been studied. The hydrated samples were submitted to 4% of CO2 in a carbonation chamber, and were analysed, previous carbonation and after 14 and 90 days of carbonation time, by infrared spectroscopy and X-ray diffraction; the developed morphology was performed with the 14 days carbonated samples. The results evidenced that ettringite reacts with CO2 after 14 days of exposition time and evolves totally at 90 days; the developed hydrated phases C(3)AH(6) in samples with major CAC content, also reacts with CO2. Due to carbonation, calcium carbonate - mainly vaterite but also aragonite-, depending on the initial formulation, aluminium hydroxide and gypsum were detected. (C) 2012 Elsevier Ltd. All rights reserved.