Exploring Use of Biochar from Different Feedstock as Cement Replacement in Cementitious Composites

The construction industry is a major contributor to global carbon emissions, with cement production alone responsible for significant greenhouse gas outputs. To address this challenge, biochar, a carbon-rich material derived from biomass through pyrolysis, has emerged as a potential supplementary cementitious material (SCM). This study examines the impact of biochar feedstock types (rice husk, hardwood, and softwood) and particle sizes (<20 μm, 53–149 μm, and 149–300 μm) on the performance of cementitious composites. The biochar materials were comprehensively characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyze their chemical structure and functional groups, X-ray Fluorescence (XRF) spectrometry to determine their chemical composition, and Scanning Electron Microscopy (SEM) to evaluate surface morphology and porosity. Isothermal calorimetry tests assessed the hydration behavior of cement pastes with 5%, 10%, and 20% biochar replacement, monitoring heat flow and cumulative heat release over 78 hours. Additionally, compressive strength tests evaluated the mechanical properties of biochar-incorporated composites, flow table tests examined workability, and thermal conductivity tests assessed the insulating properties of the resulting materials.