“We bump tested as we went looking for obvious defects to take out with the fourth roller when the mix was still hot,” Zera says. “We feel that really enhanced our profilograph results.”
Plote also used inlaid tape for the skip-dashes between lanes. “The fourth roller also allowed for the installation of the tape, and it didn’t slow down the paving installation because we didn’t need a third roller to drop back and work with the tape installation,” Zera says.
Pay for Performance (PFP)
Unlike most projects Plote has completed, the pay factor for project I-55 came from a new system of judging pavement — Pay for Performance (PFP). This pay factor system, used by IDOT, examines the pavement in three different categories resulting in a certain percentage of the pay scale for each category. The categories include voids at 30 percent pay factor, voids in mineral aggregates (VMA) at 30 percent pay factor, and density at 40 percent pay factor.
“Your asphalt is judged in 10,000-ton lots, and each lot of the PFP is 10 1,000-ton sub-lots,” Zera says. “Your 1,000-ton sub-lots are judged on random cores from field checking for density from one random sample from the HMA plant. The random samples are taken after the mix is dumped into the truck, and IDOT will pull over the truck and take a sample from it. This will determine the voids and VMAs of the 1,000 ton sub-lot sample.”
The field samples, testing the density, are taken every 1,056 feet in a random location of the lane paved.
For I-55, Plote used 126,000 tons of combined SMA binder and SMA surface totaling in 12 lots of PFP. As a result, this was one of the largest PFP project to be completed in District 1.
Contractors have a base line they must meet, with a little leeway above and below the base line. This also affects the pay factor.
“When you go over the limit of tolerance or under the limit of tolerance, that affects your pay factor for the 1,000-ton sub-lot,” Zera says. “You can be penalized for your inconsistencies. If they are extreme enough you can be forced to remove and replace the 1,000-ton sub-lot at no cost to the owner.”
Along with a different system for determining the pay factor, Plote also encountered a few challenges maneuvering equipment and crews with a limited 3-mile length of closure in one direction.
“We would extend our three-mile lane closure with several of our operations from our initial grind to the installation of lane markers and reflectors,” Zera says. “We would start at the east end working our way west. When were far enough down the line we would have to extend the lane closure an additional mile, but we would have to go back to the beginning to pick up the closure from the first mile so there was never more than a three-mile closure.”
It was challenging choreographing the different subs that worked within the closures to make sure they didn’t exceed the lane closure limits. Zera credits the success of completing this difficult job and maintaining a safe and efficient work zone to the communication between the day and night superintendents.