The hot weather North Carolina endured for much of the summer of 2010 was actually a plus for the work proceeding on the repaving of Interstate 40 through Duplin and Sampson County, according to Ken Batchelor, NCDOT resident engineer. For putting down open-graded asphalt friction course, as is being done now on this stretch of highway, the hotter the better. The asphalt mix contains PG 76-22 binder that makes hand work difficult. When the air temperature is hot, the job goes even smoother and quicker.
“It’s about the equivalent of working with bubblegum,” explained Batchelor. “If it’s too cool you are unable to do little if any hand work with it.”
Sampson and Duplin Counties are about 50 mi. south of Raleigh. Batchelor works out of Clinton, N.C., just east of the location of the Fayetteville office of the highway contractor on the project, Barnhill Contracting Company. The project itself is 15 mi. east of Batchelor’s office. He is the resident engineer for highway contract projects in NCDOT Division 3, which consists of six counties. His work is concentrated in Duplin and Sampson counties.
Re-Establishing an Effective Road Top System
“What is currently on this stretch of highway has been out there for 12 to 14 years. And I don’t know how long this asphalt mix has been around before that,” said Batchelor. “There’s nothing here with this technology that’s really new. I don’t think it’s being utilized a whole lot, but more and more they are going to this type of paving simply because of the safety factors involved with it.”
The time had come to do something. The existing friction course was raveling, actually coming up in some sections and there were minor failures in the roadway.
“I think the division was having some problems with recurring accidents during rain so they put down the friction course,” said Batchelor. “When they put that friction course down they might have done some minor patching to the existing asphalt, but they did not resurface it.
“What we’re really doing right now is going back and maintaining this highway. We’re milling off the existing friction course there, down three-quarters of an inch to an inch deep, and putting down two inches of S12.5C just to help re-establish the pavement structure of the asphalt,” he explained.
The open grades asphalt friction course is predominantly aggregate. When it rains it allows the water to go down below the aggregate and run out underneath the tires, rather than being thrown up in someone’s windshield by the tires; therefore increasing visibility. This characteristic also helps with skid resistance and reduces hydroplaning by vehicles.
Highway Work Details Help Keep Things Rolling
This stretch of highway is just under 21 mi. (33.8 km). Work started in September 2009. The existing friction course was milled off and the S12.5C was put down. A portion of the eastbound lanes and nearly all the westbound lanes were completed. When work started up again in 2010, they finished out what needed to be done in the westbound lanes and came back and started placing fiction course on what they’d done previously.
At present, 15 mi. (2.4 km) of eastbound lanes have yet to have the friction course milled off, have the S12.5C put down and then the friction course placed on top of that. This entire I-40 highway work project could, conceivably, finish up by the first of December, according to Batchelor. But the NCDOT specs state that friction courses cannot be put down after Oct. 15.
“If we get close enough to where we could finish we’d do what we have to do to finish,” said Batchelor. “That would be a call to be made at a later time.”
On the DOT side of the operations there is an assistant resident engineer and three or four inspectors on the project at any time. On the contractor side, counting roadway and plant employees, there are at least 25 workers on this project. This is a rough estimate and does not include any of the truck drivers involved.
Approximately 6 mi. (9.7 km) of milling can be completed each day. That’s for one lane. When they come back and put down the S12.5C about 1.5 mi. (2.4 km) per day in one lane can be resurfaced. For example, the median lane was done on Sept. 22 and the outside lane done on the following day in an effort to match the center line joint.
Those Tons of Concrete and Asphalt Start to Add Up
For the S12.5C asphalt being put down 2 in. (5 cm) in thickness across the two travel lanes and the paved shoulder, 126,000 tons (114,305 t) are being used. The open-graded friction course consists of 38,000 tons (34,473 t).
The milling contractor had two Terex milling machines on-site during the project work. On the paving part of the contract work the contractor is using a Roadtec material transfer vehicle (MTV) for the asphalt and a Caterpillar paver.
Two Cat rollers also are being utilized. A rubber tire backhoe and front end loader are being used on-site to pick up any asphalt that’s been dropped and to help clean out trucks as well. The front end loader isn’t used for construction per se, merely for maintenance during the process of the work.
The median lane is completed first because the crown on the road goes from the median to the outside lane, allowing the water to drain off. They pave the median lane so that they won’t be trapping water against the joint. Safety for workers on the job is one of the project’s biggest challenges, according to Batchelor. An ordinance was passed allowing the speed limit to be reduced to 55 mph on the construction site.
“This is an enforceable speed limit,” adds Batchelor. “We have a $250 speeding penalty on this project and if someone’s caught speeding it’s an automatic $250 fine. We have signs up reminding motorists of this and the North Carolina Highway Patrol helping us out pretty well throughout the area too.
“All the cell phones and the texting going on do concern us. The fact is, all that is between us and the traffic are the ’skinny drums.’ They’re not going to stop anyone; all they really do is delineate where the traffic should be, from where the work is being done and help people to keep moving on by — hopefully.” CEG
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