Multi-characterizations of the hydration, microstructure, and mechanical properties of a biochar–limestone calcined clay cement (LC3) mixture

Biochar is a green material derived from agricultural waste and other biomasses via thermochemical conversion under anaerobic conditions. Improving the utilization of biochar can reduce agricultural waste and carbon emissions. Limestone calcined clay cement (LC3) is low-carbon hybrid cementitious material with significant potential. The hydration, microstructure, and physical properties of a novel green biochar-added LC3 were investigated in this study. The biochar replacement amounts were 1% and 2%. The composition of the material was characterized using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and other methods. The engineering performance of the material was evaluated by testing its compressive strength, ultrasonic pulse velocity, and surface resistivity. The aim of this study was to analyze and explore whether the organic combination of biochar and LC3 can further improve the performance of cement and identify new approaches to reusing waste biomass. The addition of biochar delayed cement hydration, increased the content of the hydration products, and slightly reduced the compressive strength of LC3. Moreover, we observed that the hydration products of cement could be formed owing to the porous characteristics of biochar. Furthermore, the 1% biochar increased the surface resistivity of the material, whereas the 2% biochar decreased it. The combination of biochar and LC3 can further improve the environmental benefits of cement and promote the transition from the cement industry to green production.