Laboratory and Field Tests of Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Components and 2205 Pickled Stainless Steel

Abstract

Multiple corrosion protection systems for reinforcing steel in concrete and the laboratory and field test methods used to compare these systems are evaluated. The systems include conventional steel, epoxy-coated reinforcement (ECR), ECR with a primer containing microencapsulated calcium nitrite, multiple coated reinforcement with a zinc layer underlying DuPont 8-2739 epoxy, ECR with a chromate pretreatment to improve adhesion between the epoxy and the steel, two types of ECR with high adhesion coatings produced by DuPont and Valspar, 2205 pickled stainless steel, concrete with water-cement ratios of 0.45 and 0.35, and three corrosion inhibitors (DCI-S, Rheocrete 222+, and Hycrete). The rapid macrocell test, three bench-scale tests (Southern Exposure, cracked beam, and ASTM G 109 tests), and a field test are used to evaluate the corrosion protection systems. The linear polarization resistance test is used to determine microcell corrosion activity. An economic analysis is performed to find the most cost-effective corrosion protection system. Corrosion performance of 2205 pickled stainless steel is evaluated for two bridges, the Doniphan County Bridge and Mission Creek Bridge in Kansas. The degree of correlation between results obtained with the Southern Exposure, cracked beam, and rapid macrocell tests is determined based on the results from a study by Balma et al. (2005). In uncracked mortar and concrete containing corrosion inhibitors, total corrosion losses are lower than observed at the same water-cement ratios in concrete with no inhibitors. In cracked concrete, however, the presence of corrosion inhibitors provides no or, at best, very limited protection to reinforcing steel. In uncracked concrete with a water-cement ratio of 0.35, corrosion losses are generally lower than observed at a watercement ratio of 0.45. In cracked concrete, a lower water-cement ratio provides only limited or no additional corrosion protection. Compared to conventional ECR, ECR with a primer containing microencapsulated calcium nitrite shows improvement in corrosion resistance in uncracked concrete with a w/c ratio of 0.35. At a higher w/c ratio (0.45), however, the primer provides corrosion protection for only a limited time. The three types of ECR with increased adhesion show no consistent improvement in corrosion resistance when compared to conventional ECR. The multiple coated reinforcement exhibits total corrosion losses between 1.09 and 14.5 times of the losses for conventional ECR. Corrosion potentials, however, show that the zinc provides protection to the underlying steel. A full evaluation of the system must await the end of the tests when the bars can be examined. Microcell corrosion losses measured with the linear polarization resistance test shows good correlation with macrocell corrosion losses obtained with the Southern Exposure and cracked beam tests. An economic analysis shows that, for the systems evaluated in the laboratory, the lowest cost option is provided by a 230-mm concrete deck reinforced with the following steels (all have the same cost): conventional ECR, ECR with a primer containing calcium nitrite, multiple coated reinforcement, or any of the three types of ECR with increased adhesion. Corrosion potential mapping results show that no corrosion activity is observed for either bridge deck. To date, the 2205p stainless steel has exhibited excellent corrosion performance. Total corrosion losses in the Southern Exposure and cracked beam tests at either 70 or 96 weeks are appropriate to evaluate the corrosion performance of corrosion protection systems. For the current comparisons, the rapid macrocell test was better at identifying differences between corrosion protection systems than either of the bench-scale tests.