The effect of NaHCO3 accelerated carbonation method on the early mechanical properties of recycled aggregate concrete

In order to simplify the carbon sequestration process of recycled aggregate concrete (RAC), this paper proposes a method of using sodium bicarbonate (NaHCO₃) solution to cure RAC and accelerate carbonation. The compressive and flexural tests of 135 specimens were completed, and the effects of three carbonation environments and carbonation age on the early mechanical properties of RAC were studied. The results indicate that the carbonation environment of NaHCO₃ solution can significantly improve the early compressive strength and flexural strength of RAC, but it will reduce ductility. Before 21d, the early compressive strength and strength development of RAC after carbonation of NaHCO₃ solution were slightly lower than those in the carbonation environment of the carbonation box, but significantly improved at 28d. The carbonation age has little effect on the flexural strength of RAC, but at the same age, the flexural strength of RAC was highest after carbonation in NaHCO₃ solution. Through thermogravimetric analysis, it was found that the calcium carbonate content in RAC after carbonation of NaHCO₃ solution was 10.3 % higher than that after carbonation in the carbonation box, and 16.5 % higher than that of natural carbonation, offering an alternative pathway for carbon sequestration in RAC.