Evaluation of Corrosion-Resistant Steel Reinforcing Bars

Abstract

The corrosion performance of a new reinforcing steel is compared with that of conventional steeL The effects of both microalloying and a special heat treatment are evaluated. The microalloying includes small increases in the percentages of copper, phosphorus, and chromium compared to conventional reinforcing steel (less than 1.5 percent total), and the heat treatment involves quenching and tempering after hot rolling. The increase in the phosphorus content exceeds the amount allowed in the ASTM specifications for reinforcing steeL The steels are evaluated using the Southern Exposure and Cracked Beam tests, which are generally accepted in United States practice, plus rapid corrosion potential and macrocell tests developed at the University of Kansas. Corrosion potential, macrocell corrosion rate, and macrocell mat-to-mat resistance are measured. Mechanical properties are compared with the requirements of ASTM A 615 to measure the affects of microalloying and heat treatment on the ductility and strength of the steel. The results indicate that the corrosion resistant steel has a macrocell corrosion rate equal to half that of conventional steel. The corrosion resisting mechanisms exhibited by the microalloying appear to involve the deposition of protective corrosion products at both the anode and the cathode. The epoxy coated corrosion resistant steel had a greater time-tocorrosion than epoxy-coated conventional steel. The microalloyed steel met the mechanical requirements of ASTM A 615 for reinforcement.