Effects of Construction Procedures and Material Properties on Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks

Research dating to 1970 provides strong guidance on how to reduce cracking in bridge decks. This knowledge is being applied in a pooled-fund study with 19 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 were 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, limiting slump, 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 a discussion of the effects of construction procedures and concrete properties on the level of cracking observed in 14 bridge decks constructed in Kansas. Crack densities are uniformly below densities observed in matching conventional bridge decks, and deck performance is clearly connected to the degree to which the LC-HPC specifications are met. Phase II of the study with the construction of 20 additional bridge decks is now underway.