Don Detwiler has a passion for quality highways. He’s known for solving difficult problems and working with engineers from all over the U.S. to seek solutions for better pavements.
"Portland cement concrete pavement today is the product of 40 years of enlightened research: it is stronger, lasts three times longer, is quieter, smoother, is environmentally outstanding, reflects light, saves lives and taxpayers’ money," said Detwiler, president and CEO of New Enterprise Stone & Lime Co. Inc., New Enterprise, Pa.
This summer, standing below Penn State’s Beaver Stadium on 24 in. of white, newly poured, full-depth concrete that stretched west to the horizon, Detwiler was discussing the International Roughness Index (IRI) with a huddle of hard-hat-clad participants.
The occasion was the annual PennDOT/ACPA Van Tour sponsored by the American Concrete Pavement Association (ACPA), Northeast Chapter.
The 2001 concrete tour focused on the $700 million I-99 Corridor which will ultimately connect State College to Pennsylvania’s 1,850-mile interstate network, and for the first time provide a north-south, mid-state connector to the state’s two major east-west corridors—the Pennsylvania Turnpike (I-76), "America’s First Superhighway," and I-80.
"The IRI is not really an index," Detwiler would tell them, according to PennDOT Chief Engineer Gary Hoffman. "What we are really talking about is ride quality; it’s what people feel in the seat of their pants."
PennDOT understands ride quality. For over six years, Pennsylvania highways were judged among the worst in the nation by trucker magazine Overdrive.
Five years later, in a stunning reversal, Pennsylvania highways earned first place in the "Most Improved State Over Last Year" category, moving up to fifth place under America’s "Best Roads."
Ride quality key to success
Hoffman explained how this victory was accomplished.
"When the current administration came into power in 1994, we determined that we were going to focus on the customer and customer needs," Hoffman said.
"All surveys told us that, far and away, the most important thing the customer wanted was a smooth ride—what they felt in the seat of their pants.
"We set some real goals for ourselves on ride quality. Our first goal was that we would have a median ride quality on our interstate system that would be better than the national median for ride quality by the year 2000.
"That was a pretty hefty goal in 1994 because we were (on the IRI scale) as much as 20 in. per mile rougher than the national median and that’s pretty significant. We were about 113 in. per mile of bumps, as it were, vs. 95-96 in. per mile at the national level.
"I am happy to say that by 1999 we did, in fact, better the national median which, then, was 90 in. per mile, while Pennsylvania’s median on the interstates was 88 in. per mile.
"So, we went from 113 down to 88 in. per mile—essentially taking two feet of bumps out of every mile of interstate on the average in the state. We did that because we focused our attention on two things. First, when we programmed our projects, they were based on doing the roughest segment.
"On the interstates, we said we would repair and rehabilitate every mile that had a ride quality greater than 150 in. per mile.
"Secondly, we said that when we build new pavements, we want to improve the quality of our construction product from the smoothness standpoint as much as possible. We worked closely with the pavement paving industries. We ratcheted up the criteria for smoothness on new pavements.
"We put money where our mouth was because we put a bonus scenario into effect by saying we would pay up to 6% bonus on pavements that had a smooth ride—under 36 in. per mile using the ‘zero’ blanking band," Hoffman said.
"It cost us millions of dollars to do that on a statewide basis, but it was worth the effort. First, it gave the customer a smooth pavement right out of the chute—which is what they were asking for.
"Finally, we know that when you start out with a smoother pavement, it is going to last longer. As pavements age, the heavy trucks start to pound the pavement. You get a dynamic load that will make the pavement deteriorate more quickly. So, the longer you keep them smooth, the longer the pavements are going to perform."
Blanking bands and IRI
John Becker, regional director of the ACPA, Northeast Chapter, explained the transition in evaluating smoothness. "Up until 1996, Pennsylvania was using the ‘two-tenths’ blanking band as the acceptance criteria for new concrete pavements. We had several projects, however, with good ride numbers, but the two-tenths blanking band masked some chatter-chatter which made for an unacceptable seat-of-the-pants ride. We had to find a better way to evaluate ride.
"We benchmarked the best practices for evaluating ride and began the first of two major transitions, going from the two-tenths blanking band to the zero blanking band. Several of our contractors, including Don Detwiler, visited active projects in the Midwest to see what techniques were utilized to meet zero blanking band requirements.
"We had to learn what it takes to exceed 36 in. per mile on the zero blanking band. The two-tenths blanking band, zero blanking band and IRI (which has been used for several years to evaluate pavement smoothness for pavement management purposes) do not correlate very well. On top of these transitions, we knew that we were being challenged to produce a smoother ride to meet PennDOT’s aggressive goals for smoother pavements. We have continuously worked closely with PennDOT throughout these changes.
"We are now going through another transition," Becker continued. "For new pavements, we’re using the zero blanking band for acceptance purposes and IRI for bonus purposes. Very soon, IRI will be used for both acceptance and bonus purposes. Once again, the bar is being raised to meet the ever-increasing expectations of the traveling public for smoother pavements.
"Throughout this transition, I am proud to say that our industry delivered by exceeding PennDOT’s criteria for smoother concrete pavements using the zero blanking band. Continuously improving the smoothness of new concrete pavements, I am confident that we will deliver again."
NAFTA, heavy trucks and the global economy
Years before the first contract was let for the Penn State Corridor in 1998, PennDOT had decided to design the highway in concrete because of anticipated heavy truck loads and the need for longer-lasting pavements.
Looking at the new global economy, NAFTA and the increasing flow of goods from Mexico to Canada, PennDOT saw this corridor as key to the entire north-south trucking network. With the importance of international trade, the State College I-99 Corridor would eventually be a major conduit for shipping goods from Mexico through West Virginia to New York and Canada.
With this in mind, smoother, longer-lasting pavements and ride quality were at the top of PennDOT’s contract criteria. No pavement rougher than 36 in. per mile on the zero blanking band would be accepted. If a contractor didn’t meet this standard, he would be required to go out and grind the surface of the pavement for smoothness to get it down to this level.
If a contractor built pavements smoother than 30 in. per mile, PennDOT gave them a bonus in 2% increments—up to 6% of the unit price of the concrete paving for pavements smoother than 18 in. per mile.
I-99 paving contractors respond
Baker Concrete Construction Senior Project Manager Bruce Chapin said Baker erected one of the company’s REX model-S 10 CY batch plants in order to produce the concrete needed to get the job done to meet smoothness specifications.
"The traffic sequencing specifications required that the pavement of the mainline be discontinuous," Chapin said. "But in spite of the disrupted paving sequence, we received an incentive of 2% for the smooth pavement surface we ultimately achieved."
The smoothness specification on these projects was the zero blanking band. Chapin believed it was the joint cooperation of the prime contractor (HRI Inc.), PennDOT inspection forces and Baker employees’ commitment to quality that resulted in an exceptionally fine pavement surface and ride quality for the traveling public.
With a keen eye on ride quality, New Enterprise’s Vice President for Construction Geoff Clarke said he plans to start his paving crews on Scotia Road (Section B-12) and Spring Creek (Section AO2) this fall.
With an eventual total of approximately 8 miles (40,263 linear ft) of mainline and ramp paving, Clarke said his experienced New Enterprise paving crews will concentrate on pavement smoothness and ride quality.
Tasked with three different I-99 paving contracts worth $8,831,287, Clarke said, "We are most proud of our field teams and their abilities to continue to prosecute the construction work in spite of many plan and site changes."
Angelo Iafrate Construction Co. was the paving contractor on the Centre County SR 6026 (CO3) Section, which included approximately 252,000 sq yd of 9-, 10- and 11-in. concrete pavement.
To meet the zero blanking band specifications and ensure ultimate pavement smoothness, like Baker and New Enterprise, Iafrate Project Manager Rob Shunk erected his own on-site batch plant. The 7.5 miles of 24-in. mainline pavement consisted of 11-in. RPS concrete on permeable base using a CMI SF-350 concrete paver. Even though 10 at-grade bridges broke up the mainline pavement, Shunk said the final profilograph readings yielded excellent results. The project also included almost 4 miles of 15-in. pavement on 10 ramps at two interchanges.
"The biggest challenge on these ramps was the 8% super elevations required on the loops. The use of quality concrete produced by our on-site plant alleviated problems normally associated with edge slump," Shunk said.
"The Iafrate concrete crew performed well as a team. We worked long days throughout the summer and produced a lot of quality concrete. I’m sure that busloads of Penn State fans will be enjoying this highway for years to come."
On the concrete tour, Bob Priest, president of Sanders Saws, agreed that, when fully opened in 2006, the Penn State I-99 Corridor will be a showcase for ride quality in the U.S.
"It’s ironic, because I love to explain that Sanders Saws can make a highway as smooth as a table top, but I’m impressed with PennDOT and the contractor’s success, inspiring new concrete pavement smoothness on I-99."
Priest said concrete pavement technology has improved exponentially since he took charge of his company in 1983. Located in Honey Brook, Pa., Sanders Saws manufactures diamond segmented saw blades and equipment for highway construction, building trades and other markets.
"PennDOT maintains the fifth largest state highway system in the country," Priest said, "and this concrete tour has demonstrated, beyond a doubt, that new concrete pavements can be built to meet rigid standards, provide a good feel in the seat of your pants and stand up to decades of heavy traffic use."