Abstract
A lot of researchers has reported the change in the micro-pore structure and mass transport resistivity of the hardened cement paste by carbonation in accelerated exposure condition with high CO2 concentration. In this study, the effect of the CO2 concentration in the exposure condition on the change of cement paste was investigated. In the experiments, hardened cement pastes having different water-to-cement ratios（30％, 45％ and 60％）or the presence of blast furnace slag were prepared and then exposed to drying conditions after 24 hours sealed curing. In the exposure condition, two level of CO2 concentration were set；low CO2 concentration like air exposure（CO2 concentration＝0.04％）and high CO2 concentration like accelerated carbonation exposure（CO2 concentration＝5％）. After that, the influence of CO2 concentration on the micro-pore structure and oxygen diffusion coefficient of carbonated hardened cement paste was examined. As a result, it was revealed that CO2 concentration affected the total amount of generated calcium carbonate as well as its origin and crystal structure, and the hydration progress of cement paste. Then, the CO2 concentration also affected the micro-pore structure and the oxygen diffusion coefficient of the carbonated cement paste.
