A large portion of Norway’s aging bridge infrastructure requires rehabilitation due to environmental exposure. Ultra-High-Performance Fibre-Reinforced concrete (UHPFRC) overlays have emerged as a promising solution; however, their large-scale application using locally available materials remains limited. This study investigates the mechanical performance and bond behaviour of an industrially cast, locally produced UHPFRC overlay applied to a low-strength C20/25 concrete substrate. Composite bridge deck specimens consisting of a 50 mm UHPFRC overlay on a 100 mm conventional concrete layer were produced at industrial scale and tested using four-point bending combined with digital image correlation (DIC) to evaluate flexural behaviour, crack initiation, and crack development. Pull-off teste was conducted to evaluate the bond strength of the composite material. The results showed continuous load–displacement responses without delamination, confirming monolithic behaviour, with crack initiation consistently occurring in the UHPFRC layer at an average flexural tensile strength of 5.7 MPa and reaching 13.3 MPa at maximum load. A multi-cracking phase was observed in most specimens, though strain-hardening behaviour was limited and peak load occurred shortly after the quasi-elastic domain, while failure was governed by interaction between ductile microcracking in the UHPFRC layer and localized shear cracking in the substrate. All pull-off tests resulted in substrate failure, with bond strengths ranging from 2.1 to 2.4 MPa, indicating strong interfacial performance. Overall, the findings demonstrate that locally produced, industrially cast UHPFRC can achieve robust bonding and satisfactory flexural performance, supporting its feasibility for large-scale bridge rehabilitation, although layer thickness and substrate properties influence the structural response.
Thomassen et al. (Thu,) studied this question.