Effectiveness of UHPFRC cover in delaying bar corrosion

Reinforcement corrosion is one of the major factors limiting the service life of reinforced concrete structures. This work investigates the efficiency of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) materials in mitigating corrosion of reinforcement in chloride environments. Variables of the study were, the type of fibers (Steel or PVA) added to a commercial prepackaged dry mix, concrete cover thickness, pre-existing crack widths (0, 0.5 mm and 2 mm) and the presence of constant mechanical axial stress in the exposed bar. Accelerated corrosion of specimens included the application of a constant potential with a 1:3 wet/dry cycle in order to fully oxidize the resulting corrosion byproducts. After several wet/dry cycles, specimens were tested under monotonic tension in order to study the effectiveness of UHPFRC cover in delaying corrosion of embedded reinforcement. One of the major findings was that these materials were able to fully mitigate corrosion in the absence of service cracks, however the effectiveness was gradually reduced with increasing crack width. It was also found that in the presence of cracks, steel-fiber reinforced specimens showed higher resistivity relative to PVA-fiber reinforced specimens owing to the hydrophilic nature of the synthetic fibers which enabled absorption and storage of water in the exposed concrete core.