Microstructural regulation of interfacial transition zone by biochar: A novel strategy for enhancing fire resistance

초록

Design and development of biochar-cement composites (BCC) is an innovative strategy to reduce the carbon footprint of cement-based materials. Incorporating biochar properly can help regulate the microstructure of the interfacial transition zone (ITZ) in cement composites. Yet the thermal response of porous biochar within the ITZ and the fire resistance of BCC remain unclear. This study investigated the regulatory mechanisms and reinforcing effects of biochar incorporation on the fire resistance of cementitious composites. The results revealed that biochar as fine aggregates could mitigate thermal-mismatch stress between the aggregates and the cement matrix when exposed to high temperatures, probably attributed to the low thermal expansion coefficient (1 & times; 10(-6) K-1), large plastic deformation capability, and strong elasticity of biochar. Additionally, biochar strengthened the ITZ at 500 degrees C by facilitating the formation of a high-modulus CaCO3 reinforcement layer, resulting in micromechanical properties exceeding 45 GPa. The superior thermal insulation capacity of biochar prevented local cracks at the interlayer, resulting in a similar to 31% reduction in porosity and similar to 58% reduction in decomposition of hydration products. Furthermore, full-scale fire testing provided direct support to the microscale observation that replacing fine aggregates with 30 wt% biochar could comply with the fire safety standards while maintaining acceptable structural functionality. However, excessive biochar content (40 wt%) resulted in a significant increase in porosity and cracks due to high-temperature degradation. This study elucidated the microstructural mechanisms by which biochar can enhance the fire resistance of cement-based materials through ITZ regulation, providing a novel strategy for developing high-performance, low-carbon construction materials.

키워드