ACTIVATED HYBRID CEMENTITIOUS SYSTEM, A GREEN ALTERNATIVE FOR CONCRETE PRODUCTION

摘要

Concretes made with blended Portland cement containing high volumes of fly ash provide an alternative to conventional portland cement concrete for reducing CO_2 emissions. This study evaluates mechanical and chemical activation of four fly ashes by assessing their effects on hydration and compressive strength. Results show the importance of the amorphous content in terms of compressive strength. The composition of fly ash is changed by a sieving process where certain particle sizes are retained; the amorphous silica and loss on ignition (LOI) contents varied depending on the fineness, hence affecting the performance of the fly ash in concrete. Reduction in particle size and LOI do not always lead to improvement in compressive strength. The effect of sodium sulfate, as activator, was significant at early ages for two of the fly ashes studied; the amount of portlandite consumption is reflected in the compressive strength evolution observed. However, sodium sulfate does not have the same effect on fly ashes with high amount of Fe_2O_3, where portlandite consumption is much lower.