Physicochemical properties of alkali activated GGBS and fly ash geopolymeric recycled concrete

Abstract

Reuse of recycled aggregates (RA), which are from construction and demolition wastes, and fly ash and ground granulated blast furnace slag (GGBS), which are from industry by-products, in geopolymeric recycled aggregate concrete (GRAC) could provide a sustainable solution to deal with the increasing construction waste and to reduce the CO2 emission from OPC production. This work aims to investigate the workability, mechanical performance and hydration mechanism of GGBS and fly ash based alkali activated GRAC. In this study, the RA were used to replace different levels (0%, 30%, 50%, 70% and 100%) of natural aggregates, and GGBS and fly ash based geopolymer was used to replace 100% of OPC. A series of slump, setting time, compression, XRD and SEM tests were conducted to evaluate the effects of RA content and water-binder ratio on the physicochemical properties of this green concrete. It is found that the combination of fly ash and GGBS based geopolymer and RA can provide an excellent compression resistance in concrete. The compressive failure of GRAC was dominated by the defects in RA and the ITZ. However, the denser geopolymer matrix could modify these shortages in RA and the ITZ, resulting in that GRAC have better mechanical properties than conventional concrete.