Enhanced repetitive self-healing of cementitious materials through modified biochar and optimised superabsorbent polymer

Abstract

Repetitive self-healing is important for ensuring the long-term effectiveness of cementitious materials. However, research on in-situ preservation and carbonisation of ammonia water (NH3∙H2O) to enhance repetitive self-healing of ammonium bicarbonate (NH4HCO3) has not yet been conducted. Attempted to strengthen the preservation and carbonisation of NH3∙H2O with superabsorbent polymer (SAP) and modified biochar (BC) in this study. Capturing carbon dioxide (CO2) and preserving NH3∙H2O were maximally achieved and multidimensionally analysed. Physical characteristics were found to be vital in the physicochemical mechanism of CO2 capture. Through modifications involving acid, alkali, urea, and deionised water in various types of BC (bamboo, corn straw, rice husk ash), rice husk ash was sensitive to pore structure and specific areas whereas bamboo was insensitive to physical characteristics. Furthermore, the optimised particle size range of SAP was selected through a stable equilibrium water absorption rate, achieving maximum retention of NH3∙H2O repeatedly. Subsequently, composite artificial aggregates (CAAs) were prepared by appropriately mixing BCs, SAPs, and NH4HCO3 to accelerate carbonisation. 7 % CAAs minimised autogenous shrinkage within 60 days, while 5 % CAAs maximised the healing percentage after 60 days, further elaborating on the unifying healing relationship between the individual and the entirety.