Odd markings are control joints to keep meandering cracks in line

Dan Hartzell | The Road Warrior

August 15, 2008

Q. I travel Route 378 frequently and was anticipating traffic headaches due to the recent repair and resurfacing project, but much to PennDOT's and the contractor's credit, the job was finished quickly. As I drove south on the newly surfaced roadway I noticed curious narrow white lines painted perpendicular to the roadway. They were spaced in an unusual pattern and I actually found them to be distracting. They seemed to correspond to the joints in the concrete that were covered. On a recent trip to Philadelphia similar lines appeared on the Schuylkill Expressway. Is this a new technique that PennDOT is employing, and what exactly are these lines for?

Doug Wiltraut, Whitehall Township

A. Those are indeed some eye-catching dash lines they've painted on Route 378, Doug. They jumped out at the Warrior when he went to investigate.

Not to worry though. Temporary road paint was used for the dashes, and they should quickly fade.

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The lines marked the paths for workers to follow when cutting ''control joints'' into the brand-new top layer of asphalt, using power saws and slicing directly over the expansion joints separating the concrete slabs beneath. The control joints then were filled with a flexible, rubberized asphalt material to prevent water seepage.

Concrete expansion joints, of course, allow the expansion and contraction of the slabs without cracking, or at least postpone and minimize the inevitable cracking in the slabs.

Control joints or seams are cut directly above the expansion joints, into the top layer of asphalt only; workers don't cut all the way through to the concrete. The asphalt joints won't eliminate surface cracking, but they should control it because cracks will tend to follow the joint, according to PennDOT engineer Al Picca.

''The [concrete] pavement beneath is rigid; it's going to expand and contract,'' Picca said. ''The [asphalt] paving on top is flexible, and will move at different rate. The crack is going to reflect up through the bituminous material; without the seam, the crack might meander.''

Instead, cracking will track the fault-line represented by the control joint. ''Without control joints over concrete pavement, the [asphalt] will fail sooner over time; this will prolong the life of the bituminous surface,'' Picca said.

The Warrior's never noticed this before, Doug. But it's not a new procedure, said PennDOT engineer Kevin Milnes, recalling its use in the paving of sections of Route 33 in Northampton and Monroe counties in 1986, and of MacArthur Road in Whitehall Township in the mid-1990s.

Though control joints aren't used in all cases, Milnes agreed they should extend the life of new paving. ''Not every roadway has it, but it's good practice to do it,'' he said. ''You know where the [control] joints are going to crack, and you can come back'' to maintain them by refilling with the sealant.

Many of the control joints on 378 are unevenly spaced, and some even run diagonally across the lanes. Milnes said that's because the lengths of the concrete slabs varied when the highway was built. Initial construction of what then was known as the Spur Route was completed in 1969.

Also, some of the joints sit above areas where concrete repairs were made before the asphalt was applied; the joints cover cracks or seams that resulted from the repairs, Milnes said.

The seams you noticed on the Schuylkill Expressway, Doug, are regular expansion joints, PennDOT spokesman Charles Metzger said.

The Schuylkill, which Philadelphians love to hate, consists of asphalt exclusively, Metzger said. So the seams there allow the asphalt to expand and contract with less cracking and deterioration, but there are no concrete expansion joints beneath with which to pair them.

The 378 repairs did progress quickly, Doug, in contrast to the truckload of complaints the Warrior regularly receives about road projects that seem to drag on endlessly. They did not quite finish in time for Musikfest, though.

PennDOT suspended the $1.3 million, 2.5-mile resurfacing of Route 378 (as well as Route 22 repairs) during the festival. The southbound control joints were done before the event, while those on the northbound side had to wait, but were finished this week. The 378 project is complete, said PennDOT spokesman Ron Young.

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