An accelerator prepared from waste concrete recycled powder and its effect on hydration of cement-based materials

•Wet grinding could refine waste concrete recycled powder (RP) to submicron particles.•2~6% submicron RP enhanced the early hydration of plain PC and GBFS/FA-PC systems.•This paper was expected to develop a novel approach for the utilization of RP. Utilization of waste concrete recycled powder (RP) in cementitious materials faced enormous challenge, because of low activity and huge water demand. In this paper, RP was treated by wet grinding to prepare submicron-RP (SRP), and then SRP was used as an accelerator in various cementitious systems, including Portland cement system (PC), PC-granulated blast furnace slag (PC-GBFS), and PC-fly ash (PC-FA) system. The compressive strength, hydration heat, hydration products, and microstructure of these systems were studied. Results showed that SRP with an average diameter of 594 nm was obtained by wet grinding. In PC paste, at the age of 12 h, 6% SRP could augment the compressive strength by 150% and hydration heat by 100%, in comparison with the paste without SRP; in PC-GGBS or PC-FA system, the similar results were also found. The reason was because of the excellent nucleation effect to significantly facilitate the hydration of PC and promote the formation of hydrates; moreover, due to the filling effect of SRP, the microstructure of hardened pastes was refined. The research could provide a novel approach for the utilization of RP in precast engineering.