Steady-state O2 and CO2 diffusion in carbonated mortars produced with blended cements

The diffusion coefficient D-O2, the porosity and the pore structure of mortars produced with a Portland cement and a range of blended cements containing limestone powder, microsilica, portlandite or slag were measured in the non-carbonated and the carbonated state. Additionally, the setup for measuring O-2 diffusion was adapted to measure also the CO2 diffusion of the carbonated mortars. The diffusion coefficient D-O2 and the total porosity were increased in the mortars containing microsilica and slag, while they were decreased in the other mortars due to carbonation. Invariably, the pore structure became coarser in all samples. The relationship between diffusion coefficients D-O2 and D-CO2 in the carbonated mortars was always linear, with D-O2 systematically higher by factor of 1.37. As this factor broadly agrees with what was found in the scant literature about CO2 diffusion, it could be used for estimating D-CO2 of carbonated mortar and concrete based on measurements of O-2 diffusion.