Validated thermal model for bacterial survival in fire-resistant self-healing concrete

Bacteria-based self-healing concrete offers a sustainable solution to extend the service life of infrastructure by autonomously sealing cracks through microbial calcium carbonate precipitation. However, under fire conditions, the survival of encapsulated bacteria remains uncertain due to extreme temperatures that compromise biological activity and structural integrity. This study introduces a validated heat transfer model to estimate how long encapsulated bacteria can survive during fire exposure following ISO 834 conditions. The model incorporates radial heat diffusion, thermal properties of multi-layer encapsulation, and bacterial inactivation thresholds. Experimental data from our earlier study, including additional unpublished experimental insights, are used to validate the model across temperatures ranging from 200 °C to 800 °C. Simulations showed that carbon fiber-cement paste encapsulation can slow heat entry and help bacteria survive for nearly 20 h at 200 °C and about 4 h at 800 °C. In contrast, gelatin-based encapsulations degraded rapidly and failed to protect bacteria beyond 200 °C. Sensitivity analysis demonstrated that encapsulation thickness critically influences survival, with layers ≥ 1.75 mm providing significantly longer protection. This modelling framework, validated using prior experimental results on bacterial viability under fire exposure, provides a predictive basis for evaluating microbial survival in self-healing concrete systems employing multilayer encapsulation. The findings provide practical insights into optimizing encapsulation strategies to preserve bacterial functionality and enable post-fire self-healing in concrete structures.