Experimental investigations on corrosion resistance of innovative steel-FRP composite bars using X-ray microcomputed tomography

Abstract

A steel-fiber reinforced polymer (FRP) composite bar (SFCB) is a new type of hybrid bar consisting of a steel core and an FRP shell coating. The advantages of the two materials are complementary. For example, the steel bar's good ductile properties and the FRP coating's corrosion resistance work together under tensile stress. This complementary combination provides better mechanical properties and durability than ordinary steel bars. This paper features the production of two different surface types of SFCBs, and these SFCBs' response to corrosion was accelerated by an electrochemical method encompassing three designed levels of corrosion at 5%, 15%, and 25%. The corrosion condition, including the thickness of the rust layer and the rust product distribution, was observed and qualitatively analyzed by environmental scanning electron microscopy (ESEM) and energy dispersive spectroscopy (EDS) techniques. Moreover, an X-ray microcomputed tomography (μCT) was used to investigate SFCBs corrosion, and the amount of corrosion product was quantitatively analyzed. The test results indicate that the fiber types, the micropore structure of the fiber coating layer, and the manufacturing process of the SFCBs are the main factors affecting SFCBs' corrosion resistance. The SFCBs show excellent corrosion resistance. The amount of corrosion product on the FRP coated-steel interface was much less than that of ordinary steel bars that experienced the same corrosion process. The actual corrosion rate of a carbon-type SFCB is less than 1/10 that of an ordinary steel bar, and the actual corrosion rate of a glass-type SFCB is less than 1/100 of an ordinary steel bar.