Effects of Freeze-Thaw Cycles and Seawater Corrosion on the Behavior of Reinforced Air-Entrained Concrete Beams with Persistent Loads

The effects of freeze-thaw cycles and seawater corrosion on the material properties of air-entrained concrete specimens and structural behavior of reinforced air-entrained concrete beams under persistent loads were investigated in the laboratory. The air content of the specimens was designed to be 3.2 and 6.1%. Results show that when subjected to alternating actions of freeze-thaw cycles and seawater immersion, the compressive strength of concrete decreased when the number of freeze-thaw cycles increased, with the ones with higher air content showing better resistance to freeze-thaw attack. In the case of reinforced air-entrained concrete beam, the presence of persistent loads accelerated the structural behavior deterioration process. When the persistent load reached half of the ultimate load, the reduction of the ultimate load and ductility was found to be a couple of times greater than those without the persistent load. Compared to the beams with 3.2% air content, the yield load, the ultimate load, and the ductility of the beams with 6.1% air content increased by 0.5, 2.5, and 13.2%, respectively. It was concluded that air entrainment has a more considerable effect on enhancing the ductility of reinforced concrete structures in cold coastal regions.