RMC-based nutrient encapsulation for bacterial self-healing cement: Effects on cement paste properties

Abstract

Bacteria-based self-healing technology, utilizing microbial-induced calcium carbonate Precipitation is rapidly growing as a solution to enhance the durability of concrete structures. Researchers have developed various encapsulation and carrier techniques to protect bacteria within the cement matrix. However, limitations persist in the effective treatment of nutrients as the direct addition of nutrients alters hydration kinetics and weakens compressive strength of Portland Cement. Addressing this gap, this study proposed a Reactive Magnesia Cement (RMC)-based nutrient encapsulation strategy for bacterial self-healing cement. A non-ureolytic bacterium Bacillus cohnii, was employed together with calcium lactate and yeast extract used as representative nutrients. The effects of nutrients encapsulation and content on hydration, fresh and hardened properties, self-healing performances and microstructure were investigated. The results showed that the RMC-based nutrient encapsulation effectively mitigated hydration retardation, reduced macropores and mitigated the loss of compressive strength compared with direct nutrient addition. An optimal nutrient capsule content of 0.7 times the bacterial capsule content (PBC-0.7) was identified as it achieved fresh and hardened properties comparable to pure cement, while offering uncompromised healing efficiency.