Reconstruction of Wacker Drive (Chicago, Illinois) Using High Performance Concrete
The City of Chicago redesigned and rebuilt the iconic two-level Wacker Drive using high performance concrete to be resilient to a variety of extreme weather conditions, such as severe freeze-thaw cycles. To prevent the same deterioration that had occurred with the previous design, the city required that the redesigned upper deck be built for a minimum 100-year service life, be chemically resistant to de-icing salts and have no cracks during the deck's 100-year life.
Reconstruction occurred in two phases; the redesigned east-west portion of Wacker Drive was completed in 2003 and the north-south portion was completed in 2012. Anticipated climate-related impacts over the projected 100-year service life of the upper deck heavily influenced the engineering decisions undergirding the Wacker Drive project. The redesign needed to eliminate the possibility of cracks forming in the concrete upper deck, which are generally caused by thermal expansion and contraction. Hotter summers predicted for Chicago would exert more stress on the concrete over the 100-year service life than it experiences currently. Additionally, Chicago experiences numerous freeze-thaw cycles during winter months, and chlorides from de-icing chemicals can penetrate any cracks in the concrete structure and lead to reinforcement corrosion that would reduce the service life of the structure.
In order to prevent cracking caused by thermal stress and subsequent reinforcement corrosion caused by de-icing chemicals, the design team used high performance concrete and a post-tensioning system to create a zero-tension deck. The zero-tension deck will not develop cracks over time because it will always be in compression, allowing the deck to resist thermal shrinkage forces and still withstand the weight of the 300,000 vehicles and pedestrians that use the deck every day.
To achieve maximum durability and performance of the deck over the lifespan of the project, the engineering team used a high performance concrete mix. The mix used in the north-south deck construction consisted of portland cement, slag, and silica fume, which differed from the mix of the earlier east-west construction with the exclusion of fly ash in the formula. The resulting aggregate was both cleaner and harder than the one found in the east-west deck. To further protect the underlying structure from corrosion caused by de-icing chemicals, the construction team also applied a 2-inch-thick latex-modified concrete topping that is resistant to chloride penetration and can be replaced as needed. Greater durability of the materials over the service life of the section of road will be more sustainable in the long term and will save the city money in maintenance costs.
Funding for the project was shared between the Federal Highway Administration (FHWA), the Illinois Department of Transportation (IDOT), and the Chicago Department of Transportation.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on February 2, 2015.
Publication Date: November 2012
- Chicago Department of Transportation
- Illinois Department of Transportation
- Federal Highway Administration (FHWA)
- City of Chicago, Illinois
- Case study
- Air temperature
- Precipitation changes