Towards sustainable industrial application of carbon-negative concrete: Synergistic carbon-capture by concrete washout water and biochar

This study demonstrates a synergistic carbon-capture strategy, i.e., using concrete washout water and biochar together to achieve carbon-negative concrete. This strategy enabled the biochar to capture 22.85 wt% air-borne CO2, which precipitated calcium carbonate onto the biochar. This carbon-negative cement paste consisted of 30 wt% CO2-weathered biochar and 70 wt% portland limestone cement, which achieved the 7-day and 28-day compressive strengths of 22.1 MPa and 27.6 MPa, respectively. Microscopic investigation revealed the mechanisms underlying the enhanced strengths of such concrete.