Development of Specifications for a Crack Resistant Bridge Deck Concrete

摘要

Within the past five years, the Colorado Department of Transportation (CDOT) hasexperienced a continued problem with cracking of bridge decks. In 2003, CDOTimplemented the concrete mixture design Class H into the CDOT Standard Specificationfor Road and Bridge Construction. Class H was developed to provide crack resistantconcrete structures and was intended to be used in the construction of bridges and otherconcrete structures. Recently, the CDOT has noticed cracking in several bridge decksusing this concrete specification. This paper includes the design and testing of elevenconcrete mixtures in an effort to create a more crack resistant concrete and improve thecurrent specification. The concrete mixtures were designed with water-to-cementitiousmaterial’s ratio (w/cm) amounts and cement content both above and below the currentspecifications. In addition, the design approach was intended to investigate the effect ofindividual and multiple supplemental cementitious materials replacement levels andaggregate and cement type on the fresh and hardened concrete properties: restrainedshrinkage strain, compressive strength, rate of strength gain, freeze/thaw durability, andpermeability. A national state Department of Transportation (DOT) survey wasconducted to determine other DOT’s current and past research involving crack resistantconcrete as well as comments regarding their own specifications currently used for bridgedecks. A more crack resistant concrete mixture was developed through this study. Theprimary recommendations from this research were: increase the maximum allowablew/cm, decrease the cementitious content, increase the percent of allowable fly ash, andinclude a shrinkage reducing admixture.