The aim of this research was to study the carbonation resistance of a blast furnace slag concrete (80% GBFS/20%OPC), with and without alkaline activation, and its influence on the corrosion of structural reinforcement. An OPC-based concrete produced under the same specifications was used as a reference material. To do this, the material was subjected to an accelerated carbonation process under controlled conditions (65% relative humidity, 1% CO2, 25°C). The half-cell potential (Ecorr), linear polarization resistance (LPR) tests showed that both concretes based on GBFS led to depassivation of the reinforcing steel at approximately 99 days, which is the time required for full carbonation of the evaluated concretes.