Study On Corrosion Mechanism And Mechanical Property Of Corroded High-Strength Steel Bars

The durability problem caused by different reasons is increasingly prominent as the growth of existing reinforced concrete structures'service life. Large numbers of engineering examples both home and abroad show that corrosion of steel bars is the key inducement of the durability problem. HRB500 and HRB400 which have high strength and good security are new-style structural materials popularized vigorously. But the durability of high-strength steel bars hasn't been studied adequately; relied on'the Sixth Group Researching Subject of National Concrete Code Project [GBKY6001]'and'Scientific Research Found of Person with Excellent Ability of Huaqiao University [05BS303]'the mechanical property of corroded high-strength steel bars are studied in this paper. The main contents are as follows:1. The chemical constituents of high-strength steel bars are analyzed; the corrosion mechanism and influencing factors of corrosion are presented. The influence of corrosion on mechanical property of both steel bars and concrete structures are studied.2. According to the electrochemistry principle, HPB235, HRB335, HRB400 and HRB500 are corroded by the method of electrifying accelerated corrosion in the laboratory. The corrosion state and the mechanical property indexes of corroded steel bars especially of high-strength steel bars are acquired.3. The mechanical property degeneration of high-strength steel bars and common steel bars under the same corrosion condition are obtained by the comparative experiments in the laboratory.4. By analyzing the different mechanical property indexes of steel bars both before and after the corrosion, the degeneration laws between nominal mechanical property and mass loss ratio are studied separately. The comparative studies of the mechanical property degeneration of different type and diameter steel bars are made, and the influence of type and diameter of steel bars are gained.5. The actual mechanical property degeneration of corroded steel bars is studied. The similarities and differences of high-strength steel bars and common steel bars'mechanical properties are analyzed. And the relations between mechanical property degeneration and mass loss ratio of HPB235, HRB335, HRB400 and HRB500 are got. The formulas between mechanical property degeneration and mass loss ratio of each type of steel bars are obtained by fitting the experiment data; while the uniform formula between mechanical property degeneration and mass loss ratio of all steel bars are acquired in the experiment.6. The influence of corrosion on the reliability degree of reinforced concrete structure is analyzed based on structural reliability theory. And by adopting the center method the reliability indexes of reinforced concrete flexural member with high-strength steel bars both before and after corrosion are calculated according to the experiment results.