Influence of aggregate reinforcement treatment on the performance of geopolymer recycled aggregate permeable concrete: From experimental studies to PFC 3D simulations

In this paper, industrial solid wastes such as fly ash and slag powder were used as the main components to prepare geopolymer cementitious materials. The geopolymer recycled aggregate permeable concrete (GRAPC) was prepared by reinforcing the recycled coarse aggregate with the geopolymer slurry. The mechanical properties and water permeability of GRAPC were investigated by slump test, compressive strength test, water permeability test and effective void ratio test. The effects of aggregate reinforcement treatment on slurry migration and pore structure changes were investigated by building a 3D virtual model of the fresh-mixed GRAPC mix using discrete element PFC3D. It was found that with the increase of the target void ratio, the aggregate reinforcement treatment increased the compressive strength of GRAPC by 5.6 %, 5.8 %, 11.7 %, and 23.2 %, respectively, compared with the control group. Aggregate reinforcement treatment increased the permeability coefficient of GRAPC by 15 %, 6.8 %, 6.5 %, and 5.7 %, respectively, compared with the control group. The geopolymer slurry reinforced treatment aggregate can effectively enhance the mechanical strength of GRAPC and improve its permeability coefficient and effective void ratio. At 0–0.4 s vibration loading, the slurry in the aggregate reinforced group was more likely to migrate downward. At 0.4–0.8 s vibration loading, the slurry floating range inside the aggregate reinforced group was smaller and the slurry migration was more uniform. Under the action of vibration, the uniformity of the slurry and the uniformity of the pore structure inside the aggregate reinforcement group were greater than that of the control group. The geopolymer slurry reinforcement treatment enhanced the permeability coefficient and effective void ratio of GRAPC by affecting the pore structure distribution.