Coming from within

Tough, new specs met with success on W. Va.’s I-70

Asphalt Article February 05, 2015
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When Kelly Paving Inc., a division of Shelly & Sands, won the $6.5 million contract to repave a section of I-70 in West Virginia, they faced two challenges. The first was executing the job itself, covering 5.81 miles of eastbound and westbound lanes between I-70 straight line mileage point 2.17 to the intersection of I-70 and I-470 near Wheeling, W. Va. The second was doing the work in line with West Virginia’s new percent within limits (PWL) quality measurement program.

The I-70 project marked the first time that West Virginia Department of Transport (WVDOT) District 6 had required one of its contractors to meet the PWL standard, making it a learning experience for both the contractor and the DOT. For Kelly Paving, meeting these standards required extra manpower, extra precision and close cooperation with WVDOT’s lab technicians.

The stakes were high: The PWL specification required the asphalt mixtures for the job to meet 90% or greater on the quality index to earn 100% pay for each lot. Maintaining consistency at both the asphalt plant and at the jobsite was crucial to make this happen.

“We had some issues at the beginning of the PWL testing, causing us a few penalties in the beginning,” said Mark Haverty, Kelly Paving’s area manager. “But once we got the progress down, the tables turned. By the end, we earned the maximum 2% bonus on top of the regular contracted amount.”

Everything changes

The idea behind PWL is to accurately assess the quality of a paving job on an ongoing basis with the lowest possible number of tests in an effort to ensure a consistent level of quality for the mix and the work. The measurements are achieved by taking regular loose mix and 6-in.-diam. core samples of the paving project as it progresses, with the samples being sent to the client’s chosen laboratory for analysis. Instead of just averaging the test results, PWL uses statistical analysis to determine a quality index that identifies what percentage of the pavement material meets the project specifications.

“The percent within limits approach is a change from the previous practice of inspecting the mix at the asphalt plant and density gauge testing,” said Ed Morrison, Shelly & Sands’ quality control manager. “PWL requires WVDOT’s people to be on the highway with us, taking loose mix and core samples. We worked closely with WVDOT in analyzing these samples, to make sure that we knew of any problems and were able to make adjustments quickly.”

“We checked for asphalt content, gradation, bond strength and strength densities,” said Bill Dague, WVDOT District 6 materials supervisor. “We also took core samples at the joints to check density, thickness and bonding.”

The samples were taken from 2,500-ton lots. The loose mix asphalt was used to determine the gradation (25% of the total pay factor) and asphalt content (25% of total pay factor). The compacted asphalt was checked to measure the road’s mat density. It accounted for the remaining 50% of the total PWL pay factor.

“If we received 90% on the total PWL sample scores, then we got 100% payment,” said Morrison. “But if one or more of the measured factors was too far off the standard, we were penalized.

“Conversely, if we exceeded the required standards as measured by testing, we received an incentive bonus,” he added. “That was our goal, and one that we achieved after ironing out the initial bugs in our process.”

The I-70 project, Kelly’s first under the PWL rules, utilized 15% reclaimed asphalt pavement and 25% recycled steel slag.

 

Constant consistency

The 5.81 miles of I-70 Kelly Paving had to pave was a very busy stretch of highway, especially at the interchange with I-470. Add several on- and off-ramps, and the road was sufficiently hazardous that “we had to do all of the paving at night,” Morrison said.

Kelly Paving used 54,981 tons of hot-mix asphalt on the job. After they milled the surface down, the crews put down a 2.25-in. layer of 19-mm Superpave with a PG 70-22 binder. They then topped it with 1.5 in. of 12.5-mm Superpave with a PG 76-22 binder. Both mixes incorporated 15% reclaimed asphalt pavement (RAP). In addition to recycling old pavements, the surface layer included 25% recycled steel slag for skid resistance.

“The slag comes from West Virginia’s steel mills,” Haverty said. “In the past, supply was never an issue. But with the decline in the state’s steel industry, slag is getting harder to come by.”

To create the roadway, one lane at a time, Kelly Paving used a Vögele 5200-2 Vision series paver and a Terex CR662RM RoadMix material-transfer vehicle. The rollouts were variously handled by Bomag BW266AD-4, Caterpillar CB-534D, Hamm HD+ 110 VV HF and Hamm HD 120 VO vibratory rollers.

“It was vital to use a material-transfer vehicle between the trucks and the paver to ensure a consistent mat and head of material,” said Morrison. “The Terex made sure that the paver had access to a reliable supply of material, and that there were no breaks or gaps between truck loads that could affect the flow of mix. When you’re working with PWL and IRI smoothness specifications, you have to take every opportunity to maximize your consistency. Transfer devices help do that.”

 These 5.81 miles are a key section of I-70 for commuters and drayage alike.

 

Cutting an edge

With PWL disincentives/incentives built into its $6.5 million contract, Kelly Paving was motivated to do everything it could to maximize quality. Deploying the Terex transfer device was one way they did this. Another was the chosen approach to joining the separate lane lifts.

“When you are joining one lane lift to another, there are potential density issues that can occur at the edges,” said Haverty. “Even if you get a good joint, the pavement at the edges will have lower density than that found throughout the rest of the mat.”

To avoid this issue, Kelly’s crew cut down the edge of the first lane’s lift edge by a few inches. Next, they then applied asphalt cement to the cut-down edge. Only when this was done did they apply the adjoining lane, ensuring that the joint between the two was well-seated, of the right density and thoroughly bonded.

After milling, crews put down a 2.25-in. layer of 19-mm Superpave with a PG 70-22 binder. On top of that went 1.5 in. of 12.5-mm Superpave with a PG 70-22 binder.
 

Careful examination

As mentioned previously, WVDOT testers took loose mix and 6-in. core samples for every 500 tons of roadway material laid (2,500 ton lots). They also took 6-in. cores along the longitudinal lane joints—one every 2,000 lineal feet (10,000 lineal foot lots).

These samples were sent to WVDOT’s lab for quality assurance acceptance. “We examined each sample carefully to see if it met WVDOT’s PWL standards for this contract,” said Dague. “It was exacting work, but it ensured that the state was getting the quality of road it was paying for.”

The project had a maximum joint density bonus of $4,000 per lot, and on the flip side a maximum disincentive of $12,500 per lot. And everytime someone took a core out of the company’s nicely laid lift, Kelly Paving had to fill it in again—seamlessly.

Kelly Paving kept a close eye on WVDOT’s work; after all, serious money was on the line. But they did more than just watch: “We took our own samples when they did,” said Morrison. “We then took them back to our own lab at our Bennwood, W. Va., plant. Those samples gave us immediate information on how we were doing, and evidence if there was any discrepancy between our findings and those of WVDOT. Quality-control testing on our end and partnering with WVDOT District 6 were key to make this project a success.”

Working with the original

Keeping on top of quality was a constant challenge for Kelly Paving, simply because of the nature of PWL compliance. But this wasn’t their only point of concern: The condition of the original I-70 roadbed also caused them problems.

“We ran into sheeting problems with the original asphalt, after we had milled it down,” said Haverty. “A number of large slabs sheeted free of the base, which meant we had to remove them and replace that material at our own expense. In some areas, we had to add an extra half-inch of asphalt in the first lift, just to resolve the problem.”

Add the need to do the work at night, and Kelly Paving did not have an easy time fulfilling its I-70 contract. But they managed nevertheless, finishing the job by the Sept. 30, 2014, deadline and achieving the top 2% of bonuses available to them through the PWL system.

“We succeeded due to a lot of preplanning with WVDOT staff, adding extra people to do our own quality control, and watching every step of the process very carefully,” said Morrison. “The transfer device also helped us ensure maximum consistency in the asphalt mix.”

First is a victory

The I-70 project was the first time Kelly Paving had worked on a PWL contract with WVDOT, and they learned a lot from the experience. In particular, the company learned that constant quality management kept its paving within the necessary limits, and that going the extra mile in ensuring smooth joints between lanes would be worth the effort come testing time.

“We also learned that we need to factor in extra material for unforeseen problems, such as the sheeting that plagued part of the roadbed,” said Haverty. “Dealing with that problem cost us 10% more on asphalt mix than we had planned for.”

All things considered, both Kelly Paving and WVDOT benefitted from their first PWL project. Kelly earned its incentive pay while enhancing its paving consistency and quality, while WVDOT got its money’s worth by obtaining a durable, well-paved stretch of highway. West Virginia’s motorists also benefit, because they are the ones who get to enjoy driving this smooth, solid piece of highway for the foreseeable future. AT

 
About the author: 
Information for this article provided by the National Asphalt Pavement Association, Lanham, Md.
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