ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306864
44 | ASPIRE , Summer 2010 CBP Concrete Bridge Preservation Guidelines for Selection of Bridge Deck Overlays, Sealers, and Treatments by Paul D. Krauss, John S. Lawler, and Kimberly A. Steiner, Wiss, Janney, Elstner Associates Inc. The selection and use of bridge deck rehabilitation methods var- ies widely throughout the United States. Some agencies have de- veloped guidelines but they are limited in scope and detail. While each state likely views the need for deck repairs differently, a set of guidelines based on a general consensus of Department of Transportation (DOT) engineers throughout the country, backed by research and experience, is useful in promoting more con- sistent and universal procedures for decision making. A recent National Cooperative Highway Research Program (NCHRP) 1 study conducted a survey of transportation agencies and devel- oped just such a methodology for selecting bridge deck treat- ments for different bridge deck conditions and deck materials. Survey of Transportation Agencies The guidelines were developed based on a survey sent to all U.S. DOTs and Canadian highway agencies to obtain information on what criteria are used to make repair decisions about deteriorating bridge decks. A primary goal of the survey was to identify meth- odologies and procedures used by agencies to guide decisions regarding bridge deck maintenance and repair. These processes vary widely in complexity and many are unwritten or take the form of simple tables or flowcharts. Some procedures reference bridge inspection methods such as the National Bridge Inventory (NBI) condition ratings 2 or Pontis element condition ratings. 3 The survey showed that repair methods vary between highway agencies and often are based on a few limited techniques with which the agency is familiar. Further, the extent of tolerable dam- age varies widely between states with the decision to consider full deck replacement triggered when surface distress exceeds from 20% to over 50% of the total deck area. Therefore, the NCHRP Guidelines 1 proposes decision levels and repair tech- niques that are a general composite of those reported by the agen- cies. The guidelines were also developed to be flexible to allow individual states to easily modify the decision levels and repair options. While a particular repair option may work well in one part of the country, since the agency has had success specifying the repair and local contractors have the proper equipment and experience to install it successfully, the same technique may not be well suited for another agency because the local experience is not available and would have to be developed. Selection of Repair Options The selection of the various deck repair options is performed in two steps. First, the general category of repair that is needed is determined based on the current deck condition. The deck char- acterization process is driven by assessing the following factors: 1. Percent Deck Deterioration and NBI Condition Ratings – determined by the percent of non-overlapping area of patches, spalls, delaminations, and copper-sulfate half-cell potentials more negative than -0.35V and the National Bridge Inventory condition rating based on examination of the top and bottom deck surfaces. CBP CONCRETE BRIDGE PRESERVATION Bridge with lane closed to perform a deck condition survey. All Photos: Wiss, Janney, Elstner Associates Inc. ASP10-1625.indb 44 6/21/10 12:20 PM