Ambient pressure carbonation curing of reinforced concrete for CO2 utilization and corrosion resistance

Carbonation curing of concrete is an emerging technology that sequesters CO2 in cement matrix while improving the material properties. Given the fact that concrete is the world’s most used man-made material, its CO2 utilization capacity is high. Since majority of concrete products are reinforced with steel, CO2 utilization potential will be tremendously enhanced if all reinforced concrete can be treated by carbonation curing. However, the carbonation corrosion becomes a concern. This paper is to show if carbonation curing of reinforced concrete could be performed under ambient pressure, the concrete structure would be more corrosion resistant. It was found that reinforced concrete product so produced could attain 11 % CO2 uptake based on cement content. The rebar corrosion behavior in the carbonation-cured concrete was examined using a natural ponding test and an accelerated impressed current (IC) test independently. Results suggested that the ambient pressure carbonation improved concrete resistance to the chloride-induced corrosion due to the densified carbonate-rich surface layer. In the natural ponding test, a lower macrocell current and a lower total corrosion value were observed in the carbonation-cured concrete during the 33-month wet-dry cyclic exposure of a chloride solution. The chloride contents at the rebar location in carbonation-cued concrete were also decreased. In addition, carbonation curing was found to delay the corrosion-initiation stage. The IC-accelerated corrosion test verified that carbonation curing improved the concrete resistance to chloride penetration by lowering the current and inhibiting the corrosion-propagation, leading to an enhanced structural integrity and an extended service life after corrosion initiation.