Analysis of an accelerated carbonation test with severe preconditioning

In this paper, an analysis of the accelerated carbonation test according to the French Standard XP P18-458 is presented. It aims at a better understanding of the carbonation kinetics in the early days of this test. The influence of preconditioning by oven-drying was studied by means of carbonation depths monitoring (phenolphthalein spraying and thermogravimetric analysis) and measurements of relative humidity (RH) inside concrete samples. The main results question the relevance of the preconditioning because it does not establish a hydric balance between the tested samples and the carbonation chamber. Moreover, an absence of carbonation close to the sample surface was revealed during the early days of testing. This is explained by the very low water content resulted from oven-drying. This gives finally an explanation of the whole carbonation kinetics recorded during this test.