Engineering low-carbon fiber cement with biochar: understanding its physicochemical properties and their impact on the composite performance and carbon footprint

Abstract

To address the United Nations sustainable development goals in combating climate change, this study explores the use of biochar as a supplementary cementitious materials (SCMs) for developing low-carbon, non-structural building materials such as fiber cement. Since understanding the role of biochar in influencing the physicochemical characteristics of fiber cement is central to material development, herein, we have performed in-depth rheo-mechanical characterization. The static yield stress (rheological) of the fiber cement slurry increased by 98% with biochar content of 10 wt%, whereas the dynamic yield stress did not change substantially. The thixotropic properties was also improved with biochar content (vs. control), indicating more pronounced time dependent shear thinning behaviour and structural rebuilding at rest. The mechanical properties of the cured composite increased by 40% with biochar content of 8 wt%. Furthermore, a combination of solid-state spectroscopic studies and microstructural visualization provided insights about the contributing factors to strength development. Notably, biochar porosity and surface chemical functionality played a vital role in improving the OPC hydration. Finally, upon cradle to gate life cycle analysis (LCA) and cost to performance analysis (C/P), we learned that 8 wt% biochar substitution achieved the best C/P balance while reducing global warming potential (GWP) by 18%.