Combined influence of recycled concrete aggregates and high contents of fly ash on concrete properties

This paper presents an overview of the previous studies carried out on the combined effects of incorporating high contents of fly ash (FA) and recycled concrete aggregates (RCA) in concrete. The focus is on the fresh and hardened properties of concrete where fine and coarse RCA were used as partial or total replacement of fine and coarse natural aggregates (NA), respectively, and where high contents of FA are incorporated as binder or filler. In order to understand the combined effects of both FA and RCA, the values of some properties of the concrete mixes made with incorporation of FA and RCA relative to the reference concrete are plotted in 3D surfaces. The results of this study show that, due to chemical reaction between FA and RCA, using FA in RCA concrete production is advisable, especially for percentages of FA exceeding the standard limit, some of the particles of FA work as a pozzolanic binder instead of a filler.