Piezoresistive fiber contributions to the mechanical performance and self sensing functionality of ultra high performance concrete

The demand for smart infrastructure has driven the evolution of Ultra-High-Performance Concrete (UHPC) from a purely structural material to a multifunctional element capable of self-sensing. While the inclusion of conductive fillers is known to enable piezoresistivity, a comprehensive consensus on balancing electromechanical sensitivity with structural integrity remains fragmented. To address this gap, this review critically analyzes the impact of integrating piezoresistive fibers specifically Silane-treated Graphene Nano platelets (GNPs), Carbon Nanotubes (CNTs), and metallic fibers into UHPC matrices. The comparative analysis reveals that while individual nanomaterials enhance electrical conductivity for Structural Health Monitoring (SHM), they often face dispersion challenges that can compromise mechanical cohesion. Conversely, this evaluation identifies that hybridizing steel fibers with Silane-treated Nano carbon fillers yields significant synergistic effects. This combination not only facilitates superior strain-hardening and flexural toughness through macro-crack bridging but also maintains a stable conductive network for real-time stress and deformation sensing. Ultimately, this review concludes that hybrid reinforcement strategies, particularly those utilizing surface-treated variations, offer the most reliable pathway for simultaneously optimizing the mechanical durability and self-sensing precision of smart UHPC systems.