Bacteria-induced internal carbonation of reactive magnesia cement

With lower calcination temperature, reactive magnesia cement (RMC) can be a potential alternative to the Portland cement. However, RMC concrete requires accelerated carbonation curing from external sources which greatly hinder the wider applications of RMC. This study proposed a bacteria-based method for the strength gain of RMC through internal carbonation. Sporosarcina pasteurii, urea, and yeast extract were used as a carbonation agent for internal carbonation of RMC pastes. Results showed that the flowability of the fresh bio-RMC paste increased by 20% while the initial setting time remained unchanged. Besides serving as the CO₂ provider, urea can also function as superplasticizer to reduce the water demand of the bio-RMC pastes. The resulting bio-RMC pastes showed a continuous strength gain with time, demonstrating the feasibility of bacteria-induced internal carbonation of RMC. Microstructure analysis revealed abundant formation of hydrated magnesium carbonates in the bio-RMC pastes, which is responsible for the strength gain of the bio-RMC pastes.