Biochar-Cement Composites for Sustainable Construction

ABSTRACT

The decarbonization of cement-based materials is a critical challenge for sustainable infrastructure, requiring material innovations that reduce embodied carbon while preserving mechanical integrity, durability and service-life resilience under aggressive exposure conditions. Biochar, a porous carbonaceous material produced from biomass waste, has attracted increasing attention as a constituent of cementitious composites because it can contribute to carbon sequestration, internal curing and microstructural regulation; however, its wider application remains constrained by limited mechanistic understanding of how its pore structure, surface chemistry and intrinsic mechanical properties influence hydration, interfacial transition zone (ITZ) development, transport properties, rheology and buildability in extrusion-based 3D printing (3DP), and cracking behaviour. This seminar will present recent advances in biochar–cement composites through an integrated perspective spanning cement chemistry, fresh-state performance, microstructural characterization, durability assessment and multiscale mechanical analysis, with emphasis on how engineered biochar can regulate phase assemblage, pore structure and interfacial evolution rather than acting only as a porous lightweight inclusion. Particular attention will be given to interfacial densification and durability-oriented design strategies, including biochar surface modification and CO2-curing-assisted ITZ strengthening, which can improve matrix compatibility and resistance to chloride ingress and other degradation processes, thereby enhancing the durability and resilience of cementitious composites in service. The discussion will also address implications for clinker-reduced and alkali-activated binders, as well as emerging opportunities in 3DP cementitious materials where biochar can influence printability, shape retention, interlayer bonding and long-term performance, together with application-oriented demonstrations in thermally functional and durable construction materials, to outline a mechanistically grounded route for developing low-carbon biochar–cement composites with improved performance, durability, resilience and scalability for sustainable construction.

BIOGRAPHY

Prof. Dan Tsang is a Professor in the Department of Civil and Environmental Engineering, Director of Research Center on Decarbonization Technology, and Executive Director of School of Engineering at the Hong Kong University of Science and Technology, as well as Pao Yue-Kong Chair Professor in the State Key Laboratory of Clean Energy Utilization at Zhejiang University in China. He holds fellowships at the Institution of Civil Engineers (FICE), Institute of Materials, Minerals and Mining (FIMMM), Royal Society of Chemistry (FRSC), and Hong Kong Institution of Engineers (FHKIE). With more than 650 publications in leading international journals, he has been recognized among Stanford University’s Top 2% Scientists (Lifetime), ScholarGPS’s Top 0.05% Scholars (Lifetime), and Clarivate’s Highly Cited Researchers in both Engineering and Environment/Ecology categories. With a strong commitment to advancing the engineering profession and contributing to public service, Prof. Tsang also serves as the founding Editor-in-Chief of npj Materials Sustainability (Nature Portfolio), Chairman of the Hong Kong Waste Management Association (2023–2025), and Waste Management Subcommittee Chair (2023&2024) of the Advisory Council on the Environment of the Hong Kong Government.