Abstract
Alkali-activated cement is a promising alternative to replace totally or partially Portland cement. The heat flow and the degree of reaction are widely analyzed variables on the alkali-activation process. In this paper, a phenomenological-based semi-physical model of the alkali-activation process was developed. The model predicts the heat flow and the degree of reaction, by correlating the composition of the fly ash, the NaOH concentration (alkaline activator), the concentration of portlandite and curing temperature. The model considers balanced chemical reaction and the process diffusive phenomena. For validation microcalorimetric measurements at 25 °C and 35 °C was made, and secondly Freisleben-Hansen model was fitted with the experimental data. The results indicate a reaction acceleration for concentration of NaOH in (6–10) M and a reaction deceleration due to portlandite. The fly ash particle size and diffusivity-associated factors have an incidence of more than 5 % on the heat flow and degree of reaction.
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