Use of hydrated cement pastes (HCP) as a CO2 sponge

•A new concept of CO2 sponge was put forward.•CO2 uptake ratios by cement were measured and compared.•Water is essential for the re-carbonation process.•A technology roadmap for CO2 transportation was presented. In this study, the feasibility of using hydrated cement paste (HCP) as a CO2 sponge was investigated. The grounded HCP were carbonated, calcined and re-carbonated to investigate the potential of CO2 transportation through the use of HCP. Facilitated by the microstructural analysis, the capacity of CO2 sequestration and release via HCP, as well as the carbonation phases formed within the carbonated/calcined/recarbonated cement paste, were investigated. The initial results indicate that HCP could sequestrate CO2 to become carbonated cement paste (HCPcarbonated) with a high CO2 capture ratio, where a number of carbonates formed. After the calcination of HCPcarbonated, the calcined carbonated cement paste (HCPcalcined) was produced and some new phases formed with a large release amount of CO2. In terms of the re-carbonation process, moisture within the HCPcalcined played an important role concerning its re-carbonation efficiency. Finally, by means ofHCP, this research innovatively proposed a new concept to effectively transport CO2, that is, a CO2 sponge, as well as a technology roadmap, to achieve this goal.