Corrosion Resistant Alloys for Reinforced Concrete
Primary Topic: Materials-Concrete
Description: Infrastructure deterioration, which includes corrosion of reinforcing steel in concrete bridges, has been identified as a major economic and societal cost to the United States. For the past 30 years, epoxy-coated reinforcing steel (ECR) has been specified for reinforced concrete bridges exposed to deicing salts and coastal environments. Premature corrosion induced cracking of marine bridge substructures in Florida indicated, however, that ECR is of little benefit for this type of exposure; and while performance of ECR in northern bridge decks has been generally good to-date (30-plus years), still the degree of corrosion resistance to be afforded in the long term to major structures with design lives of 75 to 100 years is uncertain. This concern, combined with increased utilization of life-cycle cost analysis in project planning and materials selection, has caused renewed interest in corrosion resistant reinforcements, stainless steels in particular. The present research study is being performed jointly by Florida Atlantic University and the Florida Department of Transportation to evaluate alloys that have been identified as candidate corrosion resistant reinforcements. These include MMFX-II (ASTM A 1035), solid stainless steels 3Cr12 (UNS-S41003), 2201LDX (ASTM A955-98), 2205 (UNS 31803), and two 316L (UNS S31603) alloys; and two 316 stainless steel clad black bar products. Black bar (ASTM A615) reinforcement was included for comparison purposes. Testing methods included three types of short-term exposures: (1) a previously developed method that involves cyclic exposure to synthetic pore solution (SPS) with incrementally increasing chlorides and then to moist air, (2) anodic potentiostatic exposure in SPS with incrementally increasing chlorides, and (3) potentiodynamic polarization scans in saturated Ca(OH)2 at different chloride concentrations. Long-term exposures involve four specimen types: (1) simulated deck slabs, (2) 3-bar columns, (3) macro-cell slab specimens, and (4) field columns. Specimen types (1) and (3) are being cyclically wet-dry ponded with a sodium chloride (NaCl) solution and are intended to simulate northern bridge decks exposed to deicing salts, whereas types (2) and (4) are partially submerged continuously, the former in a NaCl solution and the latter at a coastal marine site in Florida. This report details findings for the initial 3 years of this 5 year project.
FHWA Publication Number: FHWA-HRT-07-039
Publication Year: 2007