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BE725, Corrosion of Florida’s bridge infrastructure has shown to be costly for FDOT, both due to the number of bridges and harsh environmental conditions across the State. While the mechanisms that describe corrosion within reinforced concrete bridge elements are well understood, the ability to limit corrosion in practice has led to many methods that aim to mitigate the effects of corrosion. These systems include durability-based design requirements for new bridges and rehabilitation efforts for existing bridges, summarized in this report. FDOT has implemented many of these systems on its bridges with varying degrees of success. This report also summarizes current FDOT design requirements and specifications regarding corrosion control for reinforced concrete bridge structures with a focus on substructure elements. A comprehensive study that compares multiple practices and systems across various Florida bridges has been undertaken. As a result, comparative data related to their performances have been compiled and analyzed. Without this information, it is challenging for the State to understand the benefits of its corrosion control measures and the life-cycle cost analysis of the systems. Therefore, this study aims to evaluate and compare multiple practices and systems used across the State in terms of durability, cost, and longterm performance. Although every corrosion prevention and control program described in this report will not be incorporated into this research, this study includes the most used measures, including concrete cover, supplementary cementitious materials, epoxy coating, and cathodic protection (metalized, impressed current, and galvanic).

BDV29-977-26, Florida International University researchers investigated the effects of microbially induced corrosion (MIC) on steel. They experimented with a variety of protective methods to determine their ability to prevent or mitigate MIC.

BDV29-977-26, Submerged steel piles had localized corrosion associated with microbiologically influenced corrosion (MIC). The site also had heavy marine growth. The effect of crevice environments created by the macrofoulers may support MIC. Also, concrete may be subject to deterioration by microbiologically influenced deterioration (MID). Field visits to Florida natural water sites and a review of the literature and databases indicated that there are locations in Florida that support MIC. Steel samples were installed at three sites (brackish and fresh waters). The presence of marine fouling was an important part of the corrosion system. Laboratory testing identified the effects of crevices and availability of bacteria and nutrients on MIC. The use of steel coatings and galvanic cathodic protection was assessed for mitigation of MIC in environments with marine fouling. The use of polyurea and a water-based copper-free antifouling coating was examined to identify mitigation. The anti-fouling coating showed less barnacle growth compared to polyurea and had generally lower surface populations of SRB, IRB, APB, and SFB. Complications in cathodic protection (CP) arise with the presence of MIC and marine fouling. Steel field specimens were coupled to a zinc anode at the test sites. Application of CP reduced the corrosion rate, but results indicated that there were portions of the steel array under marine fouling that did not receive sufficient cathodic polarization. In field testing of concrete immersed in the test sites, heavy marine fouling and bacteria developed on the specimen surface. No differentiation in bulk concrete characteristics relating to MID were identified. Application of a polyurea did not mitigate marine fouling or bacteria formation.

Present FDOT construction specifications require post-tensioned ducts to be grouted withing seven days of strnd replacement to prevent corrosion.

This investigation confirmed prior noted trends of extensive preferential chloride intrusion at preexisitng cracks in a majority of cases of substructure members in Florida bridges built with low permeability conventional concrete.

BDV29-977-04, 800002803, Recent corrosion failures of post-tensioned (PT) tendons in the Ringling Causeway Bridge (and corrosion development of PT tendons elsewhere in Florida) utilizing pre-packaged low-bleed specified grout products have spurred the need to evaluate what mechanisms were involved to cause the failure and to determine to what extent the problem is in PT tendons with similar materials. Severe corrosion was accommodated by segregated grout that was characterized as having high moisture content, low total chloride content, high free sulfate concentrations and high pore water pH. Accumulation of bleed water and grout void formation, considered sometimes as the cause of PT strand corrosion, were not consistently present with corrosion formation in the recent tendon failures. Furthermore, in addition to grout segregation with enhanced sulfate concentration, another separate issue of enhanced chloride content in PT grouts had garnered significant attention. Initial testing and chloride limit recommendations did not directly address the possible combined effect of enhanced chlorides in deficient grout. Elucidation of the role of the pore water chemistry of these deficient grouts in the corrosion mechanism is needed so that appropriate inspection and management decisions can be made., The objective of the research is to identify criteria of deficient grout properties that may cause active corrosion of strand in post-tensioned tendons. Important material and corrosion parameters that may need to be more comprehensively studied as well as refinement in the proposed set of criteria is to be identified in this phase of research. The following approach was followed: 1). Identify the characteristics of deficient grout associated with steel corrosion including grout conditions formed when cast in presence of enhanced moisture presence, 2), Identify the role of sulfates in alkaline solutions and its possible adverse effects on steel corrosion activity, 3) Identify the behavior of steel in deficient grout with enhanced sulfate concentrations, and 4) Identify combined effect of enhanced chloride content and free sulfate content in deficient grout on corrosion initiation and identify practical threshold limits.

BDV29-977-05, The service life and durability of prestressed concrete in bridges are vulnerable to corrosion damages due to many factors such as construction, material, and environment. To ensure public safety, it is important to inspect these structures and to develop appropriate mitigation measures for corrosion damages. The availability of Non Destructive Testing (NDT) technology has made it possible to evaluate the condition of a bridge without invasive removal of concrete. A project bridge located in Fort Lauderdale, scheduled for demolition, provided an opportunity to carry out various on-site and post-deconstruction tests. An analytical study was carried out for demolition sequence, and segments of the bridge were transported to Florida International University (FIU). These segments were used as a test bed setup, and additional laboratory tests were conducted to evaluate some of the NDT technologies which can be extended to the testing of actual structures. The on-site field tests using impulse response showed a reduction in global stiffness, due to partial deconstruction while acoustic emission demonstrated possible use in detection of vibration due to tendon breakages. During the field tests, infrared thermography assisted in identification of ducts with deficient grout and the use of infrared thermography was further investigated in laboratory tests. The method has shown the possibility to detect wire breakages in encapsulated grout. A methodology to detect tendon damages in internal tendons in the presence of secondary reinforcement was investigated using the magnetic flux leakage method for laboratory test setup and validated on decommissioned test segments. The inductance method showed promising results for laboratory and segment tests, but obscuring of signals due to mild reinforcement is a challenge.