Rehabilitation of concrete bridges using ultra-high performance concrete: a comprehensive review from fundamental to applications

Ultra-high performance concrete (UHPC) is recognised as an advanced material for strengthening ageing and deficient concrete structures. This review synthesises recent progress in UHPC-based bridge rehabilitation, focusing on material properties, new-old concrete bonding, mechanical properties, durability, and engineering applications. The UHPC composition, mix design (water-to-binder ratio, steel fibre content, curing methods), and time-dependent properties such as creep, shrinkage, and durability to assess long-term performance are summarised. Experimental results of the interface bond between UHPC and normal concrete (NC) with various surface treatments is discussed, and the mechanical behaviour of the UHPC-NC interface is analysed under static and fatigue loading. Structural responses of UHPC-reinforced components, including cracking load, ultimate load, ductility, and failure modes, are discussed in relation to material properties, pre-damage degree, interface treatments, and strengthening strategies. The review also highlights improvements in fatigue resistance and durability. Finally, engineering applications of UHPC in bridge rehabilitation, such as overlays, decks, girders, and substructures, are outlined to provide a consolidated foundation for future research and practical use of UHPC-based strengthening technologies.