HPC and UHPFRC cracking and durability behaviour against corrosion

Abstract

This paper analyses the cracking behaviour of reinforced elements made of High-Performance Concrete (HPC) and Ultra High-Performance Fibre Reinforced Concrete (UHPFRC) and its influence on the corrosion of reinforcements. Besides, Conventional Concrete (CC) was characterised analogously as a reference. Reinforced beams of size 100 × 150 × 750 mm3 were precracked by a 4-point bending test until different strain levels (0.5 and 1.5 ‰). Afterwards, samples of size 150 × 150 × 50 mm3 were obtained by cutting the beam in their central zone, where the bending moment is constant. These samples were exposed to chlorides to induce corrosion. Before the exposure to a chloride-rich environment, the cracked areas and widths were analysed and mappings of the cracks were obtained. During the chloride exposure, the rebar corrosion potential was continuously monitored to identify the risk of rebar corrosion. Different crack patterns were obtained in CC, HPC and UHPFRCs. CC and HPC presented wider crack widths than UHPFRC, while UHPFRC presented tighter and more distributed cracks. In the case of samples with 0.5 ‰ of strain, CC and HPC showed high corrosion risk and it was detected at the very beginning in the CC and between 60 to 200 days in the HPC regardless of the strain level. On the contrary, UHPFRC remained stable up to at least 300 days showing no corrosion after signals in 550 days of exposure, even in samples with high strain level, confirming the durability improvement regarding CC and HPC under similar strain levels.