Abstract: Adding fly ash in recycled concrete accords with the concept of “The 13^th Five-Year Green Development Plan”. The reasonable use of fly ash and recycled aggregate wastes is of great significance for economy and environment. In this research, we designed recycled concrete specimens dosed with different content of fly ash (0%, 15%, 25%, 35% and 45%) to investigate the rule of carbonization of recycled concrete mixed with fly ash. Results demonstrate that the carbonization depth of concrete is in positive relation with carbonizing age and fly ash content; the coefficient of CO₂ diffusion is in a linear functional relation with fly ash content. Moreover, we built a prediction model for carbonization depth based on the coefficient of CO₂ diffusion.

Key words: recycled concrete, fly ash dosage, carbonization depth, prediction model, coefficient of CO₂ diffusion