Investigations of cement early hydration in the presence of chemically activated fly ash - Use of calorimetry and infrared absorption methods

The paper describes an attempt of chemical activation of fly ash and claims the usefulness of combination of such investigation methods as calorimetry and infrared absorption for investigations of early periods of cement hydration. The research samples were cement pastes made with an addition of fly ash and admixtures of chemical activators, CaCl2, Na2SO4 and NaOH, whereas a cement paste without fly ash addition and a cement-fly ash paste (both without admixtures) were used as reference samples. In order to investigate early periods of cement pastes hydration, the amount and rate of heat release were registered, and IF. spectrums were checked at appointed hydration moments. As a result, it was shown that the combination of calorimetric and IR absorption methods in the investigations of early periods of cement hydration was useful. It was confirmed that the use of chemical activators CaCl2, Na2SO4 and NaOH accelerated the hydration of cement pastes containing fly ash additive in early hours after adding water. The action of activators on hydrating cement system is different for each of investigated compounds.