Internal and external synergistic CO2 capture of cement-based materials using modified biochar

Although carbonation curing represents a promising strategy for carbon emission mitigation in concrete production, current implementations primarily demonstrate sequestration capacity limited to superficial concrete layers, resulting in the suboptimal utilization of the inherent CO2 sequestration potential of concrete. In this study, biochar, a porous material, is utilized as a CO2 carrier to achieve internal and external synergistic carbonation of concrete. Compared with standard curing, the compressive strength of the cement matrix subjected to internal and external synergistic carbonation curing increased by 47.2 %, 29.7 %, and 20 % at 3 d, 7 d, and 28 d, respectively. The carbonation degree of the cement matrix at a depth of 10-15 mm improved by 101.8 %. Following the 28 d carbonation resistance test, the carbonation depth of the concrete decreased by 46.2 %. Moreover, environmental assessments indicated that the carbonation method adopted in this study can effectively reduce greenhouse gas emissions and energy consumption by 8.8 % and 3.7 %, respectively.