Performance, microstructure and carbon sequestration potential of agro biochar based cement mortars

This study is aimed at assessing the synergy of the biochar utilization and early age CO₂ curing on the mechanical performance, hydration and CO₂ uptake in cementitious materials. Three different biochars Bamboo biochar (BBC), Peanut Husk Biochar (PHBC) and Rice Husk Biochar (RHBC) were utilized with dosages up to 5 % by mass of cement and their influence under water curing and early age CO₂ curing was studied. Analytical studies using FTIR, XRD, TGA, SEM-EDS were extended on optimum biochar mixes for characterizing the microstructure, hydration, carbonation and CO₂ uptake of various biochar based mixes. The optimum dosage was found to be 1 % for BBC & PHBC while it is 2 % in RHBC from a strength perspective. Calcium carbonate polymorphs – amorphous CaCO₃ and aragonite are found to be dominant products besides other hydration products. The biochars porous surface ability to enable hydration products precipitation is revealed. Early age CO₂ curing resulted in 23 % improved degree of hydration and 19 % improved CO₂ uptake with 2 % rice husk biochar based mix compared to control mix without biochar. The improved early age strength with 48 h CO₂ curing at flue gas CO₂ concentration of 17 % and under ambient conditions were found to be promising aspects for implementation of this method in an industrial set up for production of carbon sinking cementitious products.