Real-time investigation of reaction rate and mineral phase modifications of lime carbonation

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• 作者：?zlem Cizer ; Koen Van Balen ; Jan Elsen ; Dionys Van Gemert
• 关键词：Lime ; Carbonation ; CO2 uptake ; Calcite ; X-ray diffraction
• 刊名：Construction and Building Materials
• 出版年：2012
• 出版时间：October, 2012
• 年：2012
• 卷：35
• 期：Complete
• 页码：741-751
• 全文大小：1499 K

文摘

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 33 mol/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 faces has been found to create a dormant effect for the calcite precipitation at the first stage. Lime putty indicates faster carbonation than lime hydrate due to its small particle size and morphology properties, both at a rate which is independent of the CO₂ gas concentration. These results will contribute to the understanding of lime carbonation in lime-based mortars for applications in heritage conservation, in renovation and in modern brick and stone masonry.