Sustainable cementitious materials from bamboo leaf-derived hydrochar: Process optimization and mechanical performance

This research focuses on optimizing the production parameters and comprehensively characterizing bamboo leaf-derived hydrochar synthesized through hydrothermal carbonization (HTC), aiming to advance its application in sustainable cementitious materials (SCM). Response Surface Methodology (RSM) was employed to optimize process parameters. The hydrochar utilized in this study was synthesized under experimentally validated conditions of 205 °C, a 2.67:1 water-to-biomass ratio, and a residence time of 180 min, yielding a maximum solid recovery of 70.12 %. FTIR (Fourier Transform Infrared Spectroscopy), and PXRD (Powder X-ray Diffraction) confirmed deoxygenation, aromatization, and altered hydration phases, while Thermogravimetric Analysis (TGA) demonstrated improved thermal stability with lower volatile decomposition and higher residual mass at elevated temperatures. Brunauer Emmett Teller (BET) surface area analysis showed a transition to meso–macroporous structures with increased pore diameter and volume, beneficial for internal curing and durability enhancement. Mechanical testing revealed that 1.5 % hydrochar replacement improved compressive strength and microstructural integrity, as evidenced by FESEM (Field Emission Scanning Electron Microscopy) and micro-CT analyses, while higher dosages induced porosity and microcracking. The study found a strong predictive relationship in UPV strength correlation(R² = 0.8996). Adding 1.5 % bamboo hydrochar optimizes strength, showing its promise as a sustainable cement alternative and promoting eco-friendly composites. This work highlights bamboo leaves, an underutilized agro residue, as a precursor for carbon-based SCM. The mechanical enhancement and clinker reduction potential of bamboo leaf hydrochar make it a cost-effective and eco-friendly material for sustainable construction. • HTC parameters optimized via RSM for maximum hydrochar yield. • FTIR, XRD, TGA, BET, and FESEM analyses confirmed structural and chemical transformations. • Hydrochar addition enhanced pozzolanic activity and long-term strength development. • UPV analysis validated strong correlation with mechanical performance of mortars. • Study demonstrates eco-friendly valorization of bamboo leaf waste in cementitious systems.