Abstract
In this paper, the behavior of corroded hollow section RC (reinforced concrete) columns strengthened by an Impressed Current Cathodic Protection and Structural Strengthening (ICCP-SS) system was investigated. The Carbon Fabric-Reinforced Cementitious Matrix (C-FRCM) composite serves dual functions in the intervention method. The axial compression behavior of strengthened columns was firstly investigated through axial compression tests. The influence of corrosion ratio and C-FRCM strengthening on the test results, such as failure mode, load–displacement curve, ultimate load, and ultimate strain, were analyzed. Test results showed that the ultimate load of the corroded specimens could be enhanced significantly by C-FRCM, and the ductility of the strengthened specimens was larger than the specimens without strengthening, especially for the specimens with higher corrosion ratios. Secondly, the effects of the ICCP-SS system on the migration and distribution laws of chloride ions (Cl−) in hollow section RC columns were analyzed by the potentiometric titration method. The main parameters include charging time, current density, and salt addition. Results showed that the rebar would have a certain blocking effect on the migration of Cl−, which resulted in that the content of Cl− in the inner side of the rebar was always larger than that of the outer side; and research results also showed that the increase of impressed current density and charge time would reduce the Cl− content on both sides of the rebar, while the impressed current would cause the Cl− near the rebars to constantly move toward the vicinity of CFRP.
Highlights
The hollow section reinforced concrete (RC) columns have the advantages of better seismic performance, larger moment of inertia, lighter weight, and higher material efficiency compared with compact section RC columns
We found the effect that the salt addition has on the Cl− content on the outer side of the rebar; that is, additional salt leads to an increased Cl− content, which is less notable in specimens conducted with current density
The axial compression properties of corroded RC hollow columns strengthened by FabricReinforced Cementitious Matrix (FRCM) and the influence of an Impressed Current Cathodic Protection and Structural Strengthening (ICCP-Structural Strengthening (SS)) system on the migration and distribution laws of Cl− in RC hollow columns were studied through experiments
Summary
The hollow section reinforced concrete (RC) columns have the advantages of better seismic performance, larger moment of inertia, lighter weight, and higher material efficiency compared with compact section RC columns. Protection (ICCP) and Structural Strengthening (SS) are commonly used methods for protection Both methods have their own disadvantages: ICCP technology is unable to make up for the bearing capacity loss caused by corrosion; while for SS, the corrosion of rebars is left uncontrolled and can lead to additional problems in the future. The resulting composite material that combines inorganic cementitious materials (cement paste, mortar, or concrete) and fiber-reinforced plastics (FRP) is called a FabricReinforced Cementitious Matrix (FRCM) or Textile RC/Mortar (TRC/TRM) [9] This FRCM can be utilized both as an auxiliary anode in ICCP and as a strengthening material in the SS technique to form the ICCP-SS system [4,5,6,7,8,9]. The primary purpose of the ICCP technique was to retain the potential of rebar in concrete more negative so as to prevent further corrosion, and the influence of electric field formed between the anode and cathode on the migration and distribution mechanism of Cl− were investigated in this paper
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