Washington State Evaluation of Performance-Based Concrete for Bridge Decks

Abstract

The Washington State Department of Transportation (DOT) revamped its bridge deck concrete specifications in an effort to eliminate or reduce early-age restraint cracking in bridge decks. Restraint cracking is caused by length changes resulting from shrinkage or temperature effects that are restrained by girders and internal reinforcement and show up primarily as transverse through cracks. Bridge decks constructed with the revised concrete specification are commonly referred to as “performance-based bridge decks” because the revised specification removes prescribed requirements and adds performance criteria such as shrinkage and permeability limits. Contractors are required to submit test results to prove their concrete mix design meets the specified performance requirements. The performance-based specification was first implemented in mid 2011 and is now included in the 2014 Standard Specifications. To evaluate the effectiveness of the revised concrete specification, bridges recently constructed with the performance-based specification and the traditional specification were visually inspected for cracks. The cracking severity was used to compare the bridges and can be used to draw conclusions on the effectiveness of the revised specification to prevent or reduce early-age restraint cracking in the bridge decks. This study evaluated and documented the effectiveness of the changes made to the Washington State DOT concrete specification for bridge decks and sought to identify any improvements that could be made to the current performance-based specification. The study found that the current performance-based concrete specification resulted in fewer restraint cracks than the traditional concrete specification and worked better for precast girder bridges than for steel girder bridges.