Change in Property of Hardened Cement Specimens Having Different Mineral Composition Cured in High Concentration CO2 from the Very Early Material Age

We conducted research of CO2 capture behavior and rate of CO2 diffusion into hardened cement specimens of different pre-curing period before starting accelerating carbonation curing for ordinary portland cement (herein after OPC), OPC mixed with ground granulated blast furnace slag (herein after BB), and OPC mixed with an amorphous calcium aluminate-based accelerator (hereinafter ACC) respectively. We prepared two-type of hardened cement specimens, the first was in the case of powder shape hardened cement paste specimen which is designed to avoid carbon dioxide diffusion’s influence as much as possible and to evaluate fixation capacity of CO2, as a result CO2 content increases with getting pre-curing period longer in any cases after accelerating carbonation curing. The other one was in the case of balky mortar specimens which evaluated carbon dioxide diffusion, carbon dioxide diffusion got slower with getting pre-curing period longer in the case of OPC, BB, however ACC’s CO2 diffusion was almost constant even pre-curing period is different. The mineral composition and hydrate before carbonation differed by difference of cement type. Phase diagram after carbonation was also changed. In fact, More vaterite was formed with getting pre-curing period longer in any case, especially its phenomenon was remarkable in ACC system.