Amine-modified biochar saturated with CO2 as internal carbonation curing activator for enhancing mechanical property of cement paste

Incorporation of carbon-negative biochar into cementitious materials has been recognized as one of the most promising ways to achieve global carbon neutrality.However, negative effect on mechanical strength occurs when adding high amount (>5% by weight) of biochar to replace cement due to the weak binding of interfacial transition zone between biochar and cementitious matrix.Therefore, it is imperative to develop an approach for enhancing the interfacial transition zone.In this study, we evaluated the carbon dioxide adsorption performance of amine-modified biochar and investigated the effect of biochar (5% replacement of cement by weight) saturated with CO2 as internal carbonation curing supplier on the mechanical property of cement paste.Diethanolamine (DEA) was employed to modify biochar to enhance the CO2 adsorption capacity and subsequent constraint on CO2.Higher CO2 adsorption (1.84 mmol/g) was achieved in modified biochar compared to pristine biochar (0.33 mmol/g) at 30 , and more CO2 (80.94% versus 4.33%) was retained in pores of modified biochar after being exposure to the air atmosphere.The group incorporating modified biochar saturated with CO2 exhibited similar compressive strength even compared to blank group without adding biochar (43.92 MPa versus 41.76 MPa).Improved compressive strength (41.77%, 28 days) of specimens with adding CO2saturated modified biochar was observed compared to pristine biochar saturated with CO2, which can be attributed to the hydration acceleration resulted by filler and nucleation effect.This approach can effectively reduce the negative effect of adding high amount of biochar on the mechanical property of cement paste, further helping achieve global carbon neutrality.