Influence of Freeze-Thaw Cycles and Sustained Load on the Durability and Bearing Capacity of Reinforced Concrete Columns

The deterioration of concrete structures is mainly due to the combined action of the environment and external load. In this study, 32 reinforced concrete columns were prepared to evaluate the coupling actions on the properties of reinforced concrete structures. The durability, bearing capacity, and failure mode of reinforced concrete columns were investigated under the combined action of freeze-thaw (F-T) cycles, sustained load, and salt corrosion (water or composite salt solution). Results show that the mass fluctuation of reinforced concrete columns under a sustained load was more obvious during F-T cycles. During the early F-T cycles, the sustained load was beneficial to the F-T resistance of the reinforced concrete columns. With the increase in F-T cycles, the damage to the columns with a sustained load gradually aggravated. In the composite salt solution, the damage to the reinforced concrete columns was postponed, and its durability showed a two-stage evolution. After 100 F-T cycles, the mass loss and relative dynamic modulus of elasticity (RDME) deterioration of the columns with a sustained load sped up significantly. The combined action of salt corrosion, load, and F-T cycles has the most significant influence on the bearing capacity, stiffness deterioration, and crack development of reinforced concrete columns.