Construction of Low Cracking High Performance Concrete (LC-HPC) Bridge Decks: Field Experience

Research over the past 35 years provides strong guidance on how to reduce cracking in bridge decks. This knowledge is being applied in a pooled-fund study with 15 state Departments of Transportation and the Federal Highway Administration to develop aggregate, concrete, and construction specifications for low-cracking high performance concrete (LC-HPC) bridge decks. In Phase I of the study, 20 bridge decks are constructed using a combination of best practices. Techniques to reduce cracking include a reduction in the cement paste content of the concrete while maintaining workability, finishability, and pumpability through the use of optimized aggregate gradations, maintaining adequate air content, deemphasizing the importance of high compressive strength and low concrete permeability, controlling the temperature of the concrete at the time of placement, minimizing evaporation during placement, improved curing, and reducing the rate of drying after curing is complete. The background and specifications are presented, along with field experience and crack survey results available from the first bridge decks constructed in Kansas. Crack densities are less than 10% of densities observed in conventional bridge decks. Preliminary results of research to be applied in Phase II of the study with the construction of 20 additional bridge decks are discussed, including the use of internal curing agents and shrinkage reducing admixtures in combination with supplementary cementitious materials.