Evaluation of biochar in cementitious pastes properties

Biochar is an industrial byproduct that, after thermal treatment through pyrolysis, results in a material primarily composed of solid carbon. It has potential for use as a chemical regulator and as a carbon uptake to reduce emissions in cementitious composites. It presents itself as a potential alternative for reducing the carbon footprint of the cement industry. In this manuscript was evaluated the performance of biochar in cementitious composites in partial substitution cement Portland in levels of 1, 2 and 3% in weight. For this, cement pastes with a water/cement ratio of 0.5 were produced and tested fresh and hardened state. Specific gravity, trapped air, mini-slump and hydration kinetics (evaluated by isothermal calorimetry up to 48h) of the pastes were determined in the fresh state. Thus, in the hardened state, the compressive and flexural strength tests at 28 days, specific gravity, void ratio, MEV, DRX, FTIR and TG were carried out. In the fresh state, the sample with 3% biochar showed 13.03% higher workability and an increase of up to 77.9% in the induction period compared to the reference series. In the hardened state, the sample with 2% biochar achieved a 215.1% higher rate of entrapped air compared to the reference series. Regarding carbon uptake, the biochar samples showed an average of 9.77% more uptake than the reference series, while the 1% biochar series showed 11.01% more uptake than the reference series. This simple methodology, replacing cement with biochar, highlights the potential of using biochar to promote a cement industry with a lower carbon footprint. It employs a simple methodology that does not require significant industrial changes to the current production line of the construction industry, proving itself as an alternative for short-term industrial application. • 1% biochar resulted in a 34.4% increase in flexural strength. • Among the samples with biochar, there was a 9.77% increase in CO 2 absorption. • 1% biochar resulted in a 31.3% increase in CO 2 absorption.