View article

Carbonation reaction of lime pastes has been studied with an on-line carbonation set-up combining the measurement of the amount of CO₂ consumed by Ca(OH)₂ with an in situ XRD analysis monitoring the real-time modification of portlandite and calcite phases. The reaction rates obtained from the net CO₂ uptake by Ca(OH)₂ and that obtained from the calcite precipitation were compared for lime putty and lime hydrate pastes carbonated in CO₂ atmosphere (7, 17 and 33mol/m³). The results indicate that the carbonation reaction is initially rapid and chemically controlled at the exposed surface with a strong limitation of CO₂ diffusion into the sample by the pore water. The reaction proceeds with a chemical-reaction controlled regime at a much higher rate followed by a transition to a CO₂-diffusion controlled regime by the carbonated sample depth. Drying and formation of amorphous CaCO₃ on the portlandite …