Hydration of coal–biomass fly ash cement

This paper presents possibilities of use of fly ashes from co-combustion bituminous coal and biomass in cement production process. Both fly ashes coming from co-combustion bituminous coal and biomass and the ones from bituminous coal combustion were analysed. The following properties of cement were tested: heat of hydration, Ca(OH)₂ content, unreacted C₃S content and microstructure. The results showed that fly ashes from co-combustion coal and biomass retard cement hydration. Cement samples containing coal-biomass fly ashes demonstrate adverse features like lower heat of hydration, higher Ca(OH)₂ content and lower rate of C₃S hydration in comparison to the ones containing fly ashes from bituminous coal. The incorporation of coal-biomass fly ashes in cement results in an increase of porosity of cement paste, leading to a microstructure of lower density.