Wet carbonation of recycled cement paste powder using a CO2-loaded monoethanolamine solvent as an internal CO2 source

To address the challenge posed by the carbonation product layer formed on recycled cement paste powder (RCPP) on the efficiency and degree of carbonation, CO₂-loaded monoethanolamine (MEA) “microcapsules” were used. The CO₂ within MEA was released by heating after the formation of the dense carbonation products layer on RCPP to provide an additional internal CO₂ source to penetrate into the uncarbonated layer. Results showed that using CO₂ dissolved in 15 %, 30 %, and 45 % MEA aqueous solution increased the carbonation degree of RCPP by 10.8 %, 11.2 %, and 13.8 %, respectively, compared to RCPP wet carbonated in water. In addition to calcite, vaterite and aragonite were observed in the CO₂-loaded MEA carbonated RCPP. The long-term compressive strength of cement pastes with 30 % CO₂-loaded MEA carbonated RCPP increased, and the porosity decreased compared to cement paste with RCPP wet carbonated in water. However, MEA negatively affected the early compressive strength of the cement paste.