An Experience Survey on the Use of Permanent Steel Bridge Deck Forms

About the report:

Permanent forms for bridge decks have become increasingly more attractive to the construction industry in recent years. Many highway officials however, have reservations concerning the use of permanent steel forms. These reservations are related to the effect the forms might have on the durability of the concrete decks and to the possibility of future corrosion problems. To evaluate the potential for the occurrence of each of these two possibilities, an experience survey and review of prior research were conducted. A survey of 38 states revealed that approximately half of them either disallowed or minimized the use of steel forms because of a fear of future maintenance problems related to their use. A number of disadvantages related to the use of steel forms were cited by the responding states. A composite evaluation of the state survey and the prior research however, indicated that permanent steel forms do not singularly affect the durability of concrete bridge decks. In addition, permanently formed decks generally have less transverse cracking and increased composite action between the deck and the girders. As compared to conventionally formed decks corrosion of steel forms can be a problem if moisture and salt solutions are allowed to gain access to the forms through joints or drainage features, or by other means. Data obtained from atmospheric corrosion tests indicate that galvanized steel forming should have a life expectancy equal to that of the bridge deck if adequately protected from moisture and salt solutions. (Corrosion resulting from the penetration of chlorides through solid concrete to the depth of the forms is unlikely). The main access channels to the forms would appear to be through cracks or deteriorated concrete. It was concluded that steel forms do not have a detrimental effect on initially good quality concrete decks and, with forming installations designed to minimize possible contact with moisture and salts, corrosion should not be a significant problem during the normal life expectancy of a bridge deck.

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