This is a method for evaluating the carbonation resistance of concrete mixes by comparison with a concrete mix with known carbonation resistance. It is not a method for the determination of carbonation depths in existing concrete structures. The test is carried out under controlled exposure conditions using natural levels of carbon dioxide or under natural conditions protected from direct rainfall. If the carbonation depth of the unknown mix is equal or less than the known mix, it is be assumed that the risk of reinforcement corrosion for the new mix is equivalent to the known mix (with the same cover required for the known mix). The "reference" concrete may be any concrete with known performance in the intended place of use (environment).