Beneficiated ponded fly ash for concretes with high volume mineral additions

Abstract

The article presents the investigation results of effect of beneficiated ponded fly ash on the properties of cement pastes and concretes with high-level replacement of Portland cement. To improve the characteristics of ponded fly ash meeting technical requirements for replacing cement in concrete the triboelectrostatic beneficiation technology has been elaborated. This technology can produce low-carbon ash product (LOI = 2.52 % in this study) for the high replacing level of cement (45 %) in concretes. The beneficiated ponded fly ash has an improved granulometric and phase composition, a decreased content of unburned carbon that accelerates the hydration process of cement, increases the rheological properties of cement paste and the ability of air-entraining admixture to hold the required involved air. In a combination with the nanostructured-carbon-based plasticizing admixture the beneficiated ponded fly ash exhibits high rate of strength increase when is used in high-volume fly ash concretes.