Publication Details (including relevant citation information):
The direct hydration of high alumina cement to the cubic phase, C3AH6, at temperatures above 30°C is proposed to avoid the conversion from CAH10 to C3AH6. The carbonation of C3AH6 with CO2 between 20°C and 90°C causes an increase in strength which is higher at higher temperatures. It is caused by the presence of thermodynamically stable carbonated phases. The optimum hydration times are the minimum necessary to get C3AH6: 3 hours at 80°C and 6 hours at 60°C. Subsequent carbonation up to a total time of 24 hours after the end of mixing provides 80% of the strength obtained after 28 days of hydration at the same temperature, with the same compounds being formed. If CaCO3 is added to the cement before mixing, the strengths are even higher than for specimens without it. The effect of a super-water-reducing admixture on strength has also been studied.