Partial substitution of OPC clinker with supplementary cementitious materials (SCMs) is commonly adopted to enhance the sustainability and durability of concrete structures. This has been proven good for structures exposed to chloride environments. However, the carbonation resistance of such concretes with high clinker substitution level is perceived to be low. This perception is mainly coming from the accelerated carbonation test data. The data on long-term carbonation resistance in concretes with SCMs is limited. This study provides long-term exposure data, which indicate that concretes with SCMs can exhibit good carbonation resistance. In the current experimental program, 45 concretes with different binder types were prepared, and natural (Open and Sheltered) and accelerated carbonation (1 and 3% CO2) tests were conducted. Then, a model (named as A-to-N model) was developed to estimate the carbonation depth in the natural environment from the experimentally observed carbonation depth in an accelerated carbonation test. This would be a very useful tool for engineers for making decisions on the choice of SCMs. Further, it would be better if the natural carbonation depth can be obtained from mixture proportion data (i.e., concentrations of water, cement, SCM etc. in concrete) - and such a model is also developed. Then, probabilistic models to estimate the time to initiation of carbonation-induced corrosion are developed. Based on this, design charts to choose suitable cover depth to achieve a target corrosion-free service life are developed. In summary, this work highlights the possibility of designing SCM-based concretes with equivalent carbonation rates as in similar OPC concretes.