Concrete carbonation tests in natural and accelerated conditions

Concrete carbonation is one of the main causes of reinforcement corrosion. Determination of the rate of concrete carbonation can be made by exposing specimens in natural atmospheres; however as this results in too slow a process, testing is usually made by accelerating the process using atmospheres of relatively high CO2 concentration. No general validation exists on how to extrapolate these testing conditions to real performance. This paper tries to contribute to the understanding of accelerated carbonation testing, by making comparisons between natural and accelerated (5 and 100% CO2) conditions in a set of concretes. The results indicate that accelerated testing changes the ranking of concrete resistance towards carbonation and that therefore, the comparison has to be made among concrete with the same additions. The use of calculation methods (set-vice life models) if properly adjusted with natural tests may be a useful complementary tool. The carbonation velocity, V-CO2 derived from the square root law is a very useful parameter to compare concretes in any testing conditions.