CRACKING IN BRIDGE DECKS: CAUSES AND MITIGATION

This report summarizes the findings of a study whose primary objectives are to determine the cause of extensive transverse cracking that has been observed in some existing bridge decks, and to identify the change of material specifications and construction practice that is necessary to reduce the severity of deck cracking. To achieve these goals, recent studies on the cause of bridge deck cracking were reviewed, an experimental study was conducted to compare the shrinkage properties of different concrete mixes, and the current material and design specifications and construction practice adopted by the Colorado Department of Transportation (CDOT) were reviewed to identify areas that need improvement. A survey was conducted on seven newly constructed bridges to examine the extent of cracking in concrete decks that were constructed with the different mix designs and curing procedure that were currently used by CDOT. Based on the literature review, factors that influence deck cracking have been identified. Ways to improve existing concrete mixes to reduce the severity of deck cracking have been proposed. Further studies are recommended to develop and evaluate improved concrete mixes that can reduce deck cracking. A new mix, termed class DSL, is recommended in this report. It is suggested that the performance of selected bridge decks be systematically monitored over a duration of one year or more to assess the severity of the deck cracking problem with the concrete mixes currently being used by CDOT and to evaluate the effectiveness of new mix designs that are to be developed and tested, including class DSL.