Carbonation resistance of fly ash and blast furnace slag based geopolymer concrete

For putting geopolymer (GP) to practical use in reinforced concrete, the carbonation resistance of GP concrete should be clarified. In this study, the carbonation depths of various GP concrete and GP mortar, of which the aluminosilicate materials were fly ash (FA) and ground blast furnace slag (BFS), were measured by the accelerated carbonation test at different elapsed times. The relationship between the carbonation depth and the elapsed time were further examined based on the experimental results and by theoretical analysis. A root function was proposed to describe the carbonation rate of FA&BFS-based GP concrete. Finally, the influencing factors of carbonation resistance of FA&BFS-based GP concrete were discussed through a comparison of carbonation rate coefficients. It is mainly concluded that the carbonation resistance of FA&BFS-based GP concrete cured at room temperature is lower than usual concrete using Ordinary Portland Cement (OPC). The carbonation resistance increases with the increase of BFS ratio in active fillers (AF), NaOH content in active activator solution (AS), and BFS fineness, or with the decrease of AS/AF ratio, and water/AF ratio. Moreover, heat curing and the use of the retarder are benefit to the carbonation resistance of FA&BFS-based GP concrete.