Determination of the evolution of hydration temperature when combining high-temperature fly ash and fluidized bed combustion fly ash

摘要

Adding high-temperature fly ash to a concrete mixture has become a common matter in modern concrete technology, not only because of the positive influence on chosen parameters of the fresh and hardened mixture, but also from an economic point of view. In recent years, however, demand for this ingredient has risen to the extent that it is becoming unavailable; thus, it is necessary to seek possible alternatives. One potential solution is the partial replacement of high-temperature fly ash with fluid fly ash. However, it is legislatively impossible to use fluid fly ash as an active admixture of concrete thus far, mainly because of its inappropriate chemical composition. Upon adding high-temperature fly ash to a cement composite, the onset of the hydration process is delayed. On the other hand, fluid fly ash can cause acceleration of the hydration processes of the cement composite thanks to the nature of its chemical composition, particularly the reactive free lime content. This article focuses on the study of possible optimal combinations of these two types of ash to eliminate negative influences on the speed and evolution of hydration processes related to the use of high-temperature ashes.