ICT/IDOT Researchers Develop Approaches to Reduce Bridge Deck Cracking

It’s clear that there is a strong need for structurally sound and well-maintained bridges within the transportation system. The Illinois Department of Transportation (IDOT) maintains thousands of bridges throughout the state, but the concrete used in these bridges presents maintenance challenges. Bridge decks—the surface that vehicles travel over when crossing a bridge—have a high surface-to-volume ratio, which makes them vulnerable to cracking as a result of shrinkage during the concrete drying process.

The goal of ICT/IDOT project R27-088, “Bridge Decks: Mitigation of Cracking and Increased Durability,” was to examine the effectiveness of shrinkage-compensating cements and shrinkage-reducing admixtures (SRAs) to determine how well they reduced bridge deck cracking in conditions similar to those in Illinois. The research team, composed of investigators from the University of Illinois at Urbana-Champaign and Saint Louis University, evaluated various combinations of shrinkage-compensating cements and SRAs to determine which were most likely to reduce the amount of cracking in bridge decks.

ICT investigator Paramita Mondal of the University of Illinois at Urbana-Champaign explains, “We were able to develop a full-bridge model by employing 3D object-based graphical modeling. The model is designed to provide reliable information about bridge deck strains and will be useful in helping predict—and correct—conditions that lead to cracking.”

Phase 2 of this project, R27-139, has recently begun. In this phase, investigators will focus on expanding the successes of the first phase and continue to develop robust concrete mixes. Additionally, they will investigate the effects of lightweight aggregates used in combination with expansive components. A lab bridge deck model will be built, and analyses will be conducted to investigate the effects of internal restraint.

Dan Tobias, Engineer of Concrete and Soils with IDOT’s Bureau of Materials and Physical Research and chair of the technical review panel for the first phase of this project states, “Repeated freeze–thaw cycles and road de-icing salts combined with existing cracks wreak havoc on bridge deck concrete in Illinois and lead to accelerated deterioration. The results of this research will help to significantly increase the sustainability and service life of bridge decks constructed in the coming years in Illinois and save considerable public funds.”

-Published April 15, 2014