Utilization of nitrogen-doped biochar in concrete for carbon footprint reduction and performance improvement

The construction industry accounts for approximately 40 % of global carbon emissions, with concrete production being a major contributor. To achieve low-carbon objectives, researchers have explored incorporating biochar into concrete to enhance its performance. In this study, nitrogen modified biochar (NBC) was prepared by modifying biochar by nitrogen doping. BET and FTIR characterization confirmed that the NBC possessed a significantly larger specific surface area and more abundant nitrogenous functional groups compared to the virgin biochar (BC). These improvements endow NBC superior water absorption and retention capabilities, promoting effective internal curing in concrete. Therefore, specimens with NBC (C-NBC) showed a significant increase in early compressive strength at 3 days compared to controls, although this enhancement became less pronounced at 28 days. Thermogravimetric analysis further showed that C-NBC had a higher rate of weight loss in the range of 100–200 °C, indicating early hydration acceleration. In addition, the enhancement of the peak weight loss at 400–450 °C indicates the promotion of carbonization, highlighting the potential of NBC to improve the carbon sequestration capacity of concrete. Therefore, nitrogen-doped biochar represents a promising strategy for developing high-performance, low-carbon building materials.