After 28 days of curing process, concrete samples were dried at 50 ± 5 C for 7 days. This period was adopted to obtain mass constancy; the samples remained in the kiln until two successive weightings differed by no more than 0.5% of the lowest mass, according to the Brazilian standard NBR 9778/1987 [23]. Next, the samples were kept for 7 days in a dry climatic chamber at 23 ± 1 C and 60% ± 5% relative humidity. Subsequently, specimens were kept in an accelerated carbonation chamber. The CO2 content was 15% ± 5% (by volume) and the relative humidity ranged from 50% to 85%, according to the methodology proposed by [10,24]. According to [24], CO2 contents above 20% can cause changes in the microstructure of the concrete that are not developed under natural exposure conditions.