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

Abstract

The diffusion coefficient D O 2 , 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 CO 2 diffusion of the carbonated mortars. The diffusion coefficient D O 2 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 O 2 and D CO 2 in the carbonated mortars was always linear, with D O 2 systematically higher by factor of 1.37. As this factor broadly agrees with what was found in the scant literature about CO 2 diffusion, it could be used for estimating D CO 2 of carbonated mortar and concrete based on measurements of O 2 diffusion.

Autogenous and drying shrinkage of mortars based on Portland and calcium sulfoaluminate cements

“…It can be avoided by drying in CO 2 -free chambers/desiccators, which however prolongs and complicates the procedure and is only applicable to small/thin specimens [26,43]. The mass gain due to carbonation is expected to be slower than the moisture loss, since part of the pores need to be first emptied of water to allow CO 2 ingress [44]. The interaction between drying and carbonation at early ages is complex, since both the reduced rate of cement hydration due to early drying (see [45]) and the internal RH [46] will also affect CO 2 binding.…”

Carbonation resistance of recycled aggregate concrete

“…The carbonation coefficient KACC was determined according to SN 505 262/1 [31] and as described in [32][33][34]. The samples were demoulded after 24 hours, cured in water for two days and stored in climatic chamber at 20 °C and 57 % RH afterwards.…”

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

“…In addition, blended cements often contain a higher amount of AFt and AFm phases exhibiting substantial volume decrease at carbonation [74]. Several researchers [73,[75][76][77][78][79][80] measured a significant increase in transport properties due to carbonation in blended cement pastes, such as diffusion and permeation coefficients. Auroy et al [77] studied the impact of carbonation on unsaturated water transport in concrete.…”