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3 CHAPTER ONE INTRODUCTION BACKGROUND AND HISTORY and only 11% selected membranes as one of the first three options for deck repair (5). Concrete bridge deck deterioration is one of the most extensive maintenance problems affecting the service life NCHRP Report 297: Evaluation of Bridge Deck Protec- of bridges. Moisture and chloride intrusion can accelerate tive Strategies (6 ) reported the results of an investigation concrete bridge deck distress through corrosion of the steel of five strategies for preventing corrosion in bridge decks. reinforcement. A 2009 International Scan, Assuring Bridge Waterproofing membranes with asphalt overlays were Safety and Serviceability in Europe (1), found that European found to be effective in preventing salt intrusion into the agencies consistently reported success incorporating water- underlying deck. Nevertheless, after 10 to 15 years of ser- proofing membranes into concrete bridge deck construction vice, membranes had deteriorated as a result of aging and to both extend service life and delay the need to rehabilitate traffic. The report concluded that such membranes, when or replace bridge decks. In contrast, their general use in the properly constructed, can prevent salt infiltration indefi- United States remains limited. nitely, but their service life depended on the rate at which the membrane deteriorated. The first NCHRP synthesis report on bridge deck dura- bility, NCHRP Synthesis of Highway Practice 4: Concrete Babaie and Hawkins (6 ) explained that the accumulation Bridge Durability (2), reported that bridge deck deteriora- of water above the membrane in the bottom portion of the tion was a major maintenance item, with the most commonly asphaltic concrete was the primary cause of deterioration. reported conditions being cracking, scaling, and spalling. This phenomenon, combined with freezing and thawing and Spalling was considered to be the most serious defect, with repeated hydraulic pressure from traffic, weakens both the the cause attributed to corrosion of the reinforcing steel. bottom layer of the asphalt and the bond between the asphal- The same report stated that the use of an impermeable inter- tic concrete and the membrane. layer membrane had won favor throughout the country, with Maine, Massachusetts, New Hampshire, and Rhode Island NCHRP Synthesis of Highway Practice 220: Waterproof- specifying it for all important bridges. California, Illinois, ing Membranes for Concrete Bridge Decks (5) stated that Michigan, Ohio, and Tennessee were specifying membranes 25% of state highway agencies reported using membranes on selected bridges. on new bridge decks. The synthesis also reported that agencies are sharply divided on the merits of waterproof- In 1976, the FHWA published a policy requiring all fed- ing bridge decks. Reasons given for not using membranes eral-aid system structures that might be damaged by deicing included the inability to inspect the top surface of the deck, salts to apply a deck protective system (3). One option was to poor performance of experimental installations, and short use a waterproofing membrane. The market for waterproof- service life of asphalt overlays. Other agencies reported that ing systems expanded as new products were introduced and membranes were cost-effective in new construction, and put to use. especially so in rehabilitation. A second NCHRP synthesis dealing with durability of In a survey for NCHRP Synthesis 333: Concrete Bridge concrete bridges, NCHRP Synthesis of Highway Practice Deck Performance (7 ), respondents were asked to identify 57: Durability of Concrete Bridge Decks (4 ), reported that which waterproofing membrane systems they had used concrete bridge deck durability continued to be a problem in the past and which they were using in 2004. The infor- because of corrosion of steel reinforcement. Membranes mation identified that the only major change in the use of were reported to be available in a variety of systems; membranes had been a reduction in the number of agencies however, field experience had been highly variable, lead- using preformed systems with asphalt-impregnated fab- ing to doubt about their long-term performance. In a 1977 ric, asphalt-laminated board, and polymers. The number survey, only 19% of the respondents indicated that mem- of agencies using elastomer preformed systems and liquid branes were the preferred protective system on new decks, systems remained about the same. In a rating of 1 to 5 for