Corrosion resistance of healed UHPC with superabsorbent polymers subjected to chloride seawater attack

This paper investigates the effects of sodium polyacrylate and polyacrylate-co-acrylamide superabsorbent polymers (SAPs) on the self-healing performance and corrosion resistance of steel rebar embedded in cracked and uncracked ultra-high performance concrete (UHPC) specimens in pure water and chloride seawater. The selfhealing efficiency was assessed by measuring the swelling capability of SAPs, quantifying crack widths closure, and evaluating the corrosion behaviors of the UHPC specimens over 280 days using electrochemical impedance spectroscopy. Healing products were identified via scanning electron microscopy and X-ray diffraction. The results revealed that SAPs-based specimens achieved complete crack healing (100%) and significantly enhanced the corrosion resistance of steel rebar in pure water. However, in chloride seawater, the ability of SAPs to close cracks and improve corrosion resistance was reduced. Although SAPs delayed the corrosion process in both environments, they could not completely restore the corrosion resistance lost due to cracking, achieving 13.65% healing efficiency for the mixture with sodium polyacrylate SAP and 10.60% for the mixture polyacrylate-co-acrylamide SAP. Microscopic observation and chemical analysis revealed that C-S-H crystals were the primary healing product, with small amounts of CaCO3. The formation of Friedel's salt was also observed in chloride seawater.