Investigation of the Resistance of Several New Metallic Reinforcing Bars to Chloride-induced Corrosion in Concrete

About the report:

The Virginia Department of Transportation recently initiated a search for metallic reinforcing bars that are not only more durable and corrosion resistant than the epoxy-coated bars currently used, but also economical. In the last few years, several new bars have shown promise; one is still in the developmental stage. These bars are (1) stainless steel-clad carbon steel bars, (2) bars made of an MMFX-2 "microcomposite" steel, (3) bars made of a new "lean" duplex stainless steel called 2101 LDX, and (4) a carbon steel bar coated with a 2-mil layer of arc-sprayed zinc and then epoxy. These bars were embedded in concrete blocks, which were then subjected to severe weekly cycles of ponding with a saturated salt solution and drying. For comparison, two solid stainless steel (304 and 316LN) bars and a carbon steel bar (ASTM A 615) were also included. The times-to-corrosion of these bars were estimated through almost weekly monitoring of the macrocell current, open-circuit potential, and polarization resistance for up to 3 years. From a chloride concentration-vs.-time profile established for the test blocks, the amount of chloride ions each bar was able to tolerate was estimated and compared. Based on such information, an analysis of the long-term costs associated with the use of these bars in a bridge deck in Virginia was also conducted. This interim report was prepared to provide bridge engineers with this timely information. The information should be valuable in making a rational selection of the most cost-effective metallic reinforcing bars that will satisfy the specified design life for concrete bridge components that will be exposed to different degrees of salting.

Authors