Impact of sustained load on damage characteristics of reinforced concrete beams under the combined action of salt freeze-thaw cycles and corrosion

A large number of reinforced concrete (RC) structures in cold regions are attacked by the combined action of sustained load, freeze-thaw cycles and steel corrosion. The combined effects accelerate the deterioration process of RC and significantly reduce the service life of RC structures. This paper presents an investigation of the damage characteristics of RC beams under combined action of salt freeze-thaw cycles (SFTCs), load and corrosion. By using the large artificial climate chamber and the RC beam reverse loading device, three RC beams were subjected to SFTCs and corrosion tests under different load levels, and one beam was subjected to corrosion tests under normal temperature without load. The test results showed that the second-order natural frequency can be used as an index to evaluate the freeze-thaw damage of RC beams. The higher the load level, the greater the amount of concrete spalling and the faster the second-order natural frequency decreases. Affected by the freeze-thaw damage, the surface of test beams is not prone to rust crack, but the stress cracks become wider with the increase of SFTCs. In addition, freeze-thaw damage aggravates the non-uniformity of longitudinal reinforcement corrosion, accelerates the corrosion ratio of reinforcement. With the increase of load level, the average corrosion ratios of longitudinal rebar and stirrups increase, and the local corrosion of longitudinal reinforcement is more serious. The coupling effect is obvious when the load, SFTCs and corrosion work together, and the evaluation of the damage characteristics of concrete members should pay attention to the interaction between various factors. (C) 2020 Elsevier Ltd. All rights reserved.