Project Portfolio - Temporary North Avenue Bridge

S.T.A.T.E. Testing was fortunate to participate in two interesting (if not "one-of-a-kind") projects as part of the North Avenue Bridge replacement. The first involved the temporary runaround bridge - a temporary steel structure with a wood plank deck. The on-site construction team was left to "design-build" the wearing course. This was an unusual challenge. North Avenue carries more than 25,000 ADT, including a high percentage of trucks. The solution had to be tough and low-maintenance.

In conjunction with CDOT, Bigane Paving, and McHugh Construction, we developed a unique solution. We chose a 3-lift profile of high-strength HMA. First, was 0.75 to 1.5 inch of "IL 4.75 mm" leveling binder. This highly polymerized mix provides both strength and flexibility. The fine gradation of the mix helped it "work" into the seams between the wood timbers.

The leveling binder was topped with two lifts of N70 Surface mix, with 10% RAP. The first acted as a second leveling course, placed at a nominal 0.75 inches thick. The final surface lift was 1.5 inches thick.

We were quite pleased that the surface performed well throughout its 15-month useful life. The only maintenance required was due to bolts working loose on the underlying timber substrate.

The "old" North Avenue Bridge bascule structure over the Chicago River. (removed in 2006)

The polymer-modified HMA mixes stood up to 15 months of diverted traffic (2007)

A wood plank deck presented a challenge for selecting and placing a wearing surface (2006)