Banana peel biochar as a sand replacement: Effects on concrete hydration kinetics and strength development

As the global population continues to rise, the generation of organic waste has significantly increased, despite low recycling rates. Among these wastes, fruit peels are commonly produced in large quantities. When fruit peels end up in landfills, they decompose, releasing emissions that can harm the environment. This study investigates the incorporation of banana peel biochar into concrete at varying sand replacements (5%, 10%, and 15%) and its effects on blended concrete composites' mechanical, physicochemical, and microstructural properties. The banana peel biochar was prepared through slow pyrolysis over six hours. Various analytical techniques were employed to characterise the biochar and its incorporation into concrete composites, including X-ray fluorescence, laser diffraction particle size analysis, X-ray diffraction, scanning electron microscopy, Carbon, Hydrogen, Nitrogen, and Sulphur analysis, and compressive-strength tests. The results indicate a 24.7% increase in the 7-day compressive strength of concrete incorporating 15% banana peel biochar as a sand replacement, compared to the control mix. This improvement suggests an accelerated hydration process and enhanced early-age strength. By 28 days, the compressive strength of all biochar-blended mixes was comparable to that of the control sample. This suggests that the main advantage of adding biochar is its ability to promote early strength gain. Additionally, the increase in normalised actual calcium hydroxide observed in the thermogravimetric analysis (TGA) at 28 days confirms accelerated cement hydration as the biochar content increases. • Banana peel biochar used as a sustainable sand replacement material in concrete production • Biochar accelerates cement hydration improving early strength • 24.7% early-age strength enhancement achieved at 15% biochar sand replacement