Durability Performance of Self-Sensible Ultra-High Performance Concrete (S2UHPC) for Civil Infrastructure Rehabilitation

Abstract
The deterioration of transportation infrastructure, accelerated by extreme weather and aging assets, demands materials that can both withstand aggressive exposures and provide scalable condition assessment. Structural health monitoring (SHM) offers valuable in-situ information, but conventional systems depend on externally mounted sensors and wiring that can be costly to install and maintain and may suffer from durability and compatibility challenges in concrete environments. This research advances self-sensing ultra-high-performance concrete (S2UHPC)—a multifunctional UHPC-based material that integrates intrinsic sensing capability through electrically conductive reinforcement, reducing reliance on separate sensor installations. This study evaluated the mechanical performance, durability, self-sensing response, and microstructure of UHPC incorporating hybrid steel fibers and carbon fibers, including formulations with Ordinary Portland Cement (OPC) and Portland Limestone Cement (PLC) binders. Results show that carbon fiber dosage governs sensing reliability: steel-fiber UHPC alone produced weak and inconsistent electrical responses under cyclic loading, while a higher carbon fiber content formed a stable conductive network enabling repeatable, stress-synchronized resistivity changes. Carbon fibers enhanced flexural performance through crack-bridging mechanisms, although compressive strength decreased modestly due to dispersion- and porosity-related effects observed microscopically. Durability testing demonstrated very low chloride penetrability for both OPC- and PLC-based UHPC. Overall, the findings identify an optimal hybrid fiber range that balances flexural performance, sensing stability, and durability, supporting S2UHPC as an implementation-ready material concept for sensing-enabled overlays or rehabilitation components in bridges and pavements in harsh climates.