Influence of Amount of Calcareous Fly Ash on Heat of Hydration of Portland Cement

Abstract

For the reason a common strategy to reduce the emitted CO2 the clinker in the cement is oft replace by supplementary cementitious materials, like blast furnace slag or fly ash. Therefore, it is important to investigate the influence of these materials to the hydration in blended cements. This study is dedicated to the contribution of a calcareous fly ash to the hydration of a blended cement. To assess this contribution five calcareous fly ashes were chosen. The hydration of samples of Portland cement and Portland cement with 10% mass of cement (mc), 20% mc and 30% mc of calcareous fly ash was investigated by means of isothermal heat flow calorimetry. Calorimetric investigations were carried out with a TAM Air heat-flow calorimeter. Tests were conducted in 20°C. Water-binder ratio of cement pastes for hydration heat examinations was equal 0, 5. Research had shown that the addition of calcareous fly ash showed a retardation of the hydration reactions and increasing the initial heat period. The induction period of samples of Portland cement with 10%, 20% and 30% mc of calcareous fly ash is retarded compared to the samples of Portland cement. There is no difference in the cumulative heat normalized to the amount of Portland cement with 10% mc of calcareous fly ash compared to the Portland cement after 72 h. When amount of calcareous flay ash increases above 10% mc the cumulative heat is lower.