Evaluation of mechanical and corrosion properties of MMFX reinforcing steel for concrete

The corrosion performance of MMFX and conventional reinforcing steels is compared based on macrocell and bench-scale tests. The conventional steel includes epoxy-coated and uncoated bars. Macrocell tests are conducted on bare bars and bars symmetrically embedded in a mortar cylinder. Specimens are exposed to a simulated concrete pore solution with a 1.6 or 6.4 molal ion concentration of sodium chloride. Bench-scale tests include the Southern Exposure and cracked beam tests. A 15% (6.04 m ion) NaCl solution is ponded on the top of both the Southern Exposure and cracked beam specimens. Mechanical properties are compared with the requirements of ASTM A 615. The uniformity and consistency in chemical composition is evaluated using a scanning electron microscope and an energy dispersive spectrometer. The microstructure of corrosion products is analyzed using a scanning electron microscope. The results indicate that MMFX steel exhibits better corrosion resistance than conventional uncoated steel, but lower corrosion resistance than epoxy-coated bars. In both the macrocell and bench-scale tests, MMFX steel exhibits a macrocell corrosion rate between one-third and two-thirds that of uncoated conventional reinforcing bars, while epoxy-coated reinforcement with the coating penetrated corrodes at a rate between 5% and 25% that of conventional steel. MMFX reinforcing steel is not recommended as a replacement for epoxy-coated reinforcement unless it is used in conjunction with a supplementary corrosion protection system.