Assessing the influence of superabsorbent polymers on corrosion resistance of reinforced ultra-high performance concrete exposed to chloride and compound saltwater via electrochemical impedance spectroscopy

The corrosion resistance of ultra-high performance concrete (UHPC) with superabsorbent polymers (SAPs) submerged in deionized water, chloride saltwater, and compound saltwater was studied. The investigated mixtures included a control UHPC mixture and UHPC mixtures with 0.3 % sodium polyacrylates and 0.3 % polyacrylate-co-acrylamide. The corrosion performance was evaluated using electrochemical impedance spectroscopy, while scanning electron microscopy-energy dispersive X-ray (SEM/EDX) analysis was used to analyze micro-morphology changes and chemical composition. Polarization analysis revealed that the control specimens exhibited the highest resistance to chloride and sulfate penetration, resulting in negligible corrosion rates after 240 days (icorr from 0.0013 to 0.0063 µA/cm2). The SAP-modified specimens also showed high resistance, with an initial low corrosion rate (icorr of 0.101 µA/cm2) that decreased to negligible levels after 28 days (icorr from 0.047 to 0.088 µA/cm2). SEM/EDX results revealed that SAPs facilitate the formation of Friedel's salt and Ettringite crystals in chloride and compound saltwater, contributing to the reduction in corrosion resistance.