Traditionally, it is considered that the carbonization rate of concrete prepared with blended cement is higher than that with pure Portland cement.The reinforcement in concrete would be corroded thereby.This is why the high volume mineral admixture concrete could not been used widely yet.But cement blended with high volume mineral admixture is necessary for low carbon production and green development.Furthermore, the standard method to test carbonization of concrete has been used for a long time.Samples cured for 28d, and then carbonized for 28d in ambiance with 20% of CO2 and (65±1)% of relative humidity.Actually, no concrete begins to carbonization after curing for 28d in situ.It is different in dynamics between accelerated carbonization and natural carbonization.Therefore, the natural carbonization behavior of concrete blended with FA or GGBS or both was investigated by various w/c, dosage, natural exposed duration (carbonized age), curing age before exposing in our researching work.Porosity of carbonized samples, compositions of carbonized layer, influence of Ca(OH)2 content change on pH value of pore solution of concrete in long time were tested as well to explain the mechanism of carbonization of concrete in natural environment.