Compressive strength doesn't passivate steel. Alkalinity does. But pozzolanic cements don't absorb CO2 IIRC. Only cements with no acidic additives (e.g. silica,

Compressive strength doesn't passivate steel. Alkalinity does. But pozzolanic cements don't absorb CO2 IIRC. Only cements with no acidic additives (e.g. silica, pozzolan, GGBFS) will absorb CO2, but in this case strength is always lost.