Activated Rice Husk Hydrochar as an additive in cement mortars and its role in carbon sequestration

Abstract Rice husk, a silica-rich agricultural waste, can be transformed into hydrochar via hydrothermal carbonisation (HTC) for applications like cement additives to promote carbon sequestration. This study explores the potential of activated rice husk hydrochar as a sustainable additive in cement mortars to enhance carbon sequestration potential. Hydrochar produced at varying temperatures was characterised using BET, XRF, XRD, SEM, and FTIR to analyse its chemical composition and microstructure. FTIR revealed critical functional groups - carbonyl (C=O) and hydroxyl (O-H) - essential for long-term CO 2 sequestration. XRF analyses identified HC-220 hydrochar as having the highest silica content (19.5%), enhancing its reactivity within cementitious matrices. HC-220 was further activated with ZnCl 2 for further utilisation as activated hydrochar. When incorporated into cement mortars, the activated hydrochar significantly enhanced CO 2 sequestration via carbonate formation as in Calcium Carbonate and Calcium Hydroxide loss formation by TGA analysis, demonstrating its role as a carbon sink. These Nindings highlight hydrochar’s potential as a low-carbon additive, valorising agricultural waste and advancing climate-positive construction practices.