By analysing the concrete equation x=at~b,it is confirmed that the time-dependent exponent b of a certain kind concrete is an undetermined constant.A new concrete specimen mold was manufactured which provided the specimen with spherical concave shape and a smooth test surface,and made nondestructive test of the concrete carbonation specimen possible.In order to determine the carbonation interface properly,Alizarin yellow R is chosen as the acid base indicator.Long period tests of concrete carbonation depth were conducted(more than 120 d),from which the equation of carbonation was established.At last,by utilizing the gray system theory and studying the time dependent rule of concrete carbonation,a dynamic model of carbonation equation is established that may provide a more scientific basis for estimation of structural endurance of in-service concrete.