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Measures to reduce or eliminate bridge deck deterioration by the use of various protective systems have been the subject of a series of reports begun in 1976. This report presents current observations of latex modified deck topping concrete protective systems. Latex modified concrete topping has not provided long-term protection for the ten structures under evaluation in Colorado, Cost comparison are made between repair with latex modified concrete and deck replacement. Over a 40-year period, replacement costs are slightly less than rehabilitation costs. Greater control of the curing of deck topping material may reduce shrinkage cracking. Nightime paving, cooler calmer weather and higher humidity would increase the probability of success on latex modified concrete to rehabilitation projects. Asphalt membrane and asphalt overlay are also suggested to increase the probability of success. Implementation: Latex modified concrete is not recommended as a rehabilitation option in Colorado at this time. Further evaluation of two structures using latex modified concrete under nigh paving and tight control of curing methods is currently underway on I-25 North of Longmont.
Reliable life cycle calculations for bridge maintenance management depends upon having reasonable alternative choices for deck repair or replacement, accurate costs for those alternative choices, and accurate service life predictions for each of the alternate choices. The objective of this study was to develop a series of tools, based on existing performance condition surveys, that can be used to better establish the expected and remaining service life of protective systems during life cycle evaluations. The study has identified two deterioration mechanisms which affect service life: 1) delamination of the concrete deck resulting from corrosion of reinforcement and 2) debonding of a concrete overlay. These deterioration mechanisms are described, influencing factors discussed and various definitions presented. The study develops a relationship between the extent of early corrosion induced deterioration and area of deck that is actively corroding, as measured by half cell potentials. A time relationship for the area of deck that is actively corroding is then presented, which permits the user to establish service life. The study also presents an evaluation of expected time to develop overlay debonding based on various types of bridge structures.
Although bridge roadway surfaces (decks) were expected to provide relatively maintenance-free service for about 40 years, the Federal Highway Administration has found that some unprotected bridge decks require major repair within 5 to 10 years, and often must be replaced after 15 years of service. The major cause of this early deterioration is corrosion of the reinforcing steel bars in the bridge deck, brought about by chloride chemicals which are used to melt snow. About $6.3 billion is needed to restore the Nation's Federal-aid system bridge decks. Most States have indicated that, if present conditions are not improved, their currently reparable bridge decks will continue to deteriorate, and eventually require complete replacement at a much higher cost. A review of the problem indicates that a number of bridges in the Federal-aid system do not have a protective system on their decks. They contain either no areas or only small areas where chloride levels are high enough to cause bridge deck deterioration. If these bridge decks were protected with one of the systems now used for new bridge construction, significant savings could be realized by avoiding more expensive repairs later. Lack of funds is the primary reason that States have not installed protective systems on existing bridges. Funds available for bridge repair are generally budgeted for bridges so deteriorated that replacement of the deck is the only option. As a result, those bridge decks with little or no deterioration will continue to deteriorate, and eventually require repairs or replacements that are much more costly than the cost of the protective systems. Weaknesses also exist in the Federal Highway Administration's evaluation process to assess the performance of the technologies in extending the service life of the bridge decks.
When considering the durability of a bridge, the concrete deck is often the most vulnerable component and can be the limiting factor affecting service life. To enhance the durability of both new and existing bridge decks, a protective system is often provided to prevent or delay the ingress of chlorides and moisture to the reinforcing steel. In the state of Indiana, this protective system typically comes in the form of a concrete overlay or a thin polymer overlay. Another protective system widely used in the United States and in many countries internationally consists of a waterproofing membrane overlaid with asphaltic concrete. Due to a history of poor performance in the 1970's and the 1980's, a moratorium has been placed on the installation of waterproofing membranes in Indiana. This study reevaluates the state-of-the-practice of bridge deck protection in Indiana with the goal of enhancing the Indiana Department of Transportation's toolbox of bridge deck protective systems. Consideration was given to the state-of-the-art and state-of-the-practice in bridge deck protective systems used by other state transportation agencies as well as by international transportation agencies. Research focused on the practice of installing waterproofing membranes and the latest technologies being used. Based on the information gathered, various protective systems were evaluated, and recommendations are provided on the selection of the most appropriate systems for various bridge conditions. Furthermore, a recommendation is provided to remove the moratorium on membrane systems so that the benefits of this system can be more fully explored and realized.