Carbon nanotube reinforcement for cementitious Composites: Advancing thermal stability, mechanical strength and durability in fire-resistant concrete

This study presents a comprehensive investigation into the incorporation of carbon nanotubes (CNTs) within cement-based mortars exposed to elevated temperature conditions, addressing a critical challenge in the durability and performance of concrete materials. Two distinct mortar formulations—a conventional reference mix and a CNT-enhanced composite—were systematically subjected to high-temperature regimes and subsequently evaluated through rigorous physicomechanical testing. Durability assessments included advanced corrosion analyses targeting the embedded steel reinforcement. Notably, the CNT-reinforced mortars exhibited significantly improved mechanical properties, attributed to the unique crack-bridging mechanism and microstructural refinement introduced by the CNTs. These mechanisms collectively enhance matrix cohesion and effectively mitigate crack propagation under severe thermal stress. From a durability standpoint, the addition of CNTs substantially improved the electrochemical stability of the embedded steel reinforcement and reduced physical degradation by decreasing porosity and water absorption, thereby enhancing the overall impermeability of the cementitious matrix. Taken together, these findings highlight the multifunctional role of CNTs in enhancing both the thermal and chemical resilience of cementitious composites. Ultimately, this work provides valuable insights toward the development of next-generation, high-performance, and sustainable construction materials engineered for demanding and aggressive environments. • Carbon nanotubes (CNTs) significantly enhance the mechanical performance and fire resistance of cement mortars up to 800 °C. • CNT addition refines the microstructure, improving corrosion resistance of embedded reinforcement. Lower porosity and reduced water sorptivity increase the long-term durability of mortar composites. • Nano-scale reinforcement mitigates thermal cracking and supports structural stability under fire exposure. • The developed CNT-modified mortar offers a promising solution for durable and resilient concrete in aggressive built environments.