Deck Thickness Considerations for CIP Reinforced Concrete Bridge Decks

Abstract

The Alabama Department of Transportation (ALDOT) employs thinner decks on their highway bridges than almost all other states and countries, and unfortunately many of these decks are exhibiting significant levels of cracking and premature deterioration. Up until about two years ago, ALDOT deck depths ranged from 6 1/4 in. (159 mm) to 7 3/4 in. (197 mm), with the depth depending primarily on the girder spacing. Since that time, ALDOT has increased their minimum deck thickness to 7 in. (178 mm); however, they still employ thinner decks than most other highway agencies. As a first step in investigating bridge deck thickness and related deck design parameters, a survey questionnaire was prepared and sent to all state Departments of Transportation. Results of the survey indicate that the most common of the current design deck thickness in the United States is 8 in. (203 mm). Most states (61%) design-in an extra 1/2 in. (13 mm) of deck thickness to allow for future grinding, and most states (67%) do not employ a wearing surface on their decks. Other results of the survey questionnaire are presented and discussed.