Combination of precipitated-calcium carbonate substitution and dilute-alkali fly ash treatment in a very high-volume fly ash cement paste

Poorer reactivity of fly ash (FA) than Portland cement brings to the problems of low strength and setting time delays of very high-volume fly ash cement paste. This study combines precipitated-calcium carbonate (PCC) substitution and dilute-alkali fly ash treatment for overcoming those drawbacks. The strength was examined at 3-, 7-, 28- and 56-day. Scanning electron microscopy and Fourier-transform infrared spectroscopy were applied for characterisations. PCC substitution improved the strength and shortened the setting time; then additional dilute-alkali fly ash treatment results in better properties. Combination of PCC substitution and dilute-alkali treatment enhances cement hydration and FA pozzolanic reaction simultaneously.