Both Rockford Blacktop and Rock Road utilized high-speed mobile screeners to process HMA grindings into small piles of sized or fractionated RAP. During the 2007 advance work, the contractors and the Illinois Tollway used the temporary pavement work to test the FRAP processing procedure in the production and placement of mixes with much higher RAP quantity as compared to current Illinois DOT mixes. The high-speed FRAP processors used by both Rockford Blacktop and Rock Road were loaned to the contractors through the Astec Corporation during the test production phase.
For the contractors, initial work with production and placement of the SMA mixes did require some adjustments, according to George Malek and Joe Lindemier, resident engineer and assistant resident engineer respectively for V3, the project's engineering firm. During initial production, the crumb rubber additive was clogging screens in the tanks where it was being mixed with the AC. That was solved by removing the screens.
Out on the project, roller operators were experiencing some shoving of the mat when trying to compact the SMA mix with heavy tandem rollers. That problem was solved by using lighter vibratory rollers, operating in static mode, to perform the initial compaction before the heavier tandem rollers began their roller patterns.
The Tollway and paving contractors are on scheduled to complete the eastbound portion of the project this month and all indications point to a smooth, less congested and safe ride for the motorists.
With the success of this project, the Illinois Tollway has established new production and construction standards for higher RAP mixes and GTR in SMA mixes for all future projects. Adopting the new standards not only supports a sustainability approach to constructing quality pavements, but it also saves the road agency and its users millions of dollars in the construction and maintenance of the system.