Durability assessment of ultra-high-performance concrete (UHPC) and FRP grid-reinforced UHPC plates under marine environments

Fiber reinforced polymer (FRP) reinforced ultra-high-performance concrete (UHPC) structures not only tackle the issue of insufficient stiffness encountered in FRP reinforced normal concrete structures, but also offer a promising solution to address the durability challenges present in conventional reinforced concrete structures. While some studies have explored the mechanical properties of FRP reinforced UHPC (referred to as FRU), their durability performance remains unexplored. This paper presents a comprehensive durability assessment of FRU and UHPC plates, incorporating steel and polyethylene (PE) fibers, to compare their performance under simulated marine conditions, along with a durability evaluation of the corresponding UHPC cylinders and FRP grid samples. Tensile retention strengths of UHPC and FRU plates were evaluated after exposure. Scanning electron microscope (SEM) analyses were employed to examine fracture surfaces. The results indicate that carbon FRP (CFRP) grids significantly enhanced the tensile performance of UHPC, showcasing improvements in tensile strength, multiple-cracking, and strain-hardening behaviors. Seawater exposure led to evident reductions in the tensile strength of UHPC plates, particularly those incorporating steel fibers. Conversely, FRU plates exhibited much smaller decreases, especially those reinforced with polyethylene (PE) fibers. This study highlights the suitability of FRU reinforced with PE fibers for marine infrastructures.