How to enhance paving operations, customer satisfaction and pavement life with your best quality control practices.

One of the most critical factors influencing the quality of an asphalt pavement is its density. To improve the quality, durability and life expectancy of asphalt pavement, you can reassess your current quality control (QC) procedures and introduce a plan that includes the monitoring and measurement of the in-place density of asphalt as it’s being laid. When you improve this basic best practice, potential bonus payments can be increased while claims and/or penalties that result from compaction issues can be reduced.

How We Gained Extra Air Voids

Let’s start with some facts our industry acknowledges:

• The normal minimum target in-place density on a “dense” hot-mix asphalt pavement is 92-93% of maximum theoretical specific gravity (Gmm) or 7- 8% air voids, but the preferred in-place compacted mat density value should be between 93 and 94% or 6-7% air voids.
• A potential 35% reduction in pavement service life can be seen from final in-place density values of between 90-92% compared to an in-place density of 93-95%.
• Monitoring the in-place density of the asphalt as it is being laid is one of the most direct and effective measures of compaction.
• A 1% reduction in air voids can potentially increase pavement life by up to 10%.

Let’s look at how that final point affects life cycle costs (LLC) of your project. All things being equal, if you’ve increased the density of the pavement by 1%, you could conservatively see a 10% increase in service life. On a $1 million project, that equates to an 8.8% LLC saving of $88,000. That’s significant for an agency or department of public works (DPW) wishing to extend its pavement maintenance schedule.

One way to improve density is to double-check your numbers. This crew sets the PQI 380 non-nuclear density gauge on the mat directly behind the screed to assess how much compaction they’re starting with before the breakdown roller even touches it. Photo courtesy of TransTech Systems

You might be among the paving contractors who operate in the commercial marketplace where there’s little opportunity to check the compaction and density of your work. You might rely on past projects and performance as a guide for your choice of mix and compaction process for the upcoming job. In most cases, the responsibility falls to the paving contractor to provide a fit-for-purpose finished product that meets the client’s specification on performance and durability, and there are few specification documents in place to give guidance on best practices for commercial paving.

Consider the large number of commercial paving companies serving your local market. You could be in an area with a high level of competition where you need to differentiate your paving crews from your competitors’.

You compete based on your price, timeliness and quality. You can’t really control the weather, base conditions, which mix you get from the FOB plant, the public or the client, but you can control scheduling (such as when materials arrive), communication with the client and public, safety of the crew and public, your equipment, and most importantly your paving process. Your good reputation will lead to repeat business if you manage well the things you can control.

Good Density Equals Smoothness Bonus

One of the critical elements you can control is achieving optimum density numbers through best rolling practices and monitoring the quality. Even if you receive a bad mix to work with, you can overcome that problem because the compaction aspect is so fundamental to the success of the pavement. A bad mix with good density will outperform a good mix with poor density. So, let’s ensure you get good density.

Set your rolling pattern but be flexible enough to change it if you need to. Then test the density behind the rollers.

If you’re working on a state department of transportation (DOT) project, you will likely be required to take cores for compliance testing, but this time-consuming and invasive method of checking density is rarely performed on any commercial projects. If you have rollers with intelligent compaction (IC) systems installed, your operator may be trained in the system’s use to monitor passes and assess pavement stiffness, but typical IC systems do not give a density value of the pavement. A ground penetrating radar (GPR) system also produces a high volume of data which may be better suited to a large project due to both the amount of data and the equipment’s complexity of operation. Another method of density testing is the use of a nuclear density gauge but this comes with a long list of costly licensing and restrictive procedures that any user must adhere to.

The method I propose is using a PQI 380 non-nuclear (electrical impedance) density gauge—as sold by TransTech Systems of Latham, New York—to measure the density of the pavement. The benefits to using this type of gauge include but are not limited to:

• You receive immediate information on the level of compaction as the material is being laid, letting you make adjustments to the rolling train, if necessary.
• Anyone can use the non-nuclear density gauge; it has no restrictions on storage, use or transportation.
• It offers no risk of radiation leak if the gauge is damaged on site and offers less risk of back injury than other, heavier types of non-invasive testing equipment.
• Having on-the-spot density readings will ensure that the specified percent relative compaction can be achieved, reducing the potential for claims or penalties.

The simplest and quickest method to achieve on-site assessment of the asphalt mat’s compaction is as follows:

• Pick a location and measure the density with the non-nuclear density gauge.
• Start the rolling pattern over that location on the mat.
• Roll with one or two passes and take another reading with the device.
• Continue with another two or three passes and take another reading; note the increase in density.
• Continue the rolling and testing process until the density readings do not increase.
• If you see a slight decrease, you’re in danger of over compacting the mix. This is called the break point and is the maximum density you will achieve on this mix with this compaction equipment.

To correlate a core to this location:

• Once the peaked location on the mat cools, mark a spot to cut the core.
• One the same spot, take a set of five readings with the gauge in a clover leaf pattern.
• Take the core from the mat and determine the density by an appropriate ASTM lab test method.
• Compare the core result to the gauge measurements at that location and calculate the difference.
• This difference is called the offset. (The offset may be negative or positive.)
• Input the offset value in the “Edit Mix” menu on the gauge. The device is ow correlated to that specific mix and it should not need to be changed for any future projects involving that mix.

TransTech Systems Model 380 PQI Builds on 25 Years of Non-Nuclear Tech

By using a quality control/quality assurance device like the PQI 380 non-nuclear density gauge, you can monitor and measure the density of the asphalt pavement as you work. You can adjust your rolling pattern if necessary to achieve the optimum density for a long-lasting pavement that meets your customers’ expectations.

This supports your good reputation and puts you on the short list for future bidding opportunities. In other words, your good reputation keeping quality as a priority not only offers long-lasting pavements for our industry, but it also helps you stand out from your competition.

John Lamond is the Sales Manager at TransTech Systems, Latham, New York. He presented this topic at the National Pavement Expo (NPE) 2024 in Tampa. For more information, contact him at jlamond@transtechsys.com.

Balancing GTR, RAP, WMA over failing concrete proves successful for Missouri taxpayers

Early June 2023, the team at NB West Contracting, headquartered in Pacific, Missouri, began work on a complex overlay. The main goal was to cover up a 15.3-lane-mile, potholed, concrete section of Route 63 in Maries County and make it a smooth, safe driving surface for the taxpayers. The Missouri Department of Transportation (MoDOT), Ingevity, National Center for Asphalt Technology (NCAT) and NB West partnered to exceed that goal.

Steve Jackson, the vice president of asphalt plant operations and sustainability for NB West spoke of combining ground tire rubber (GTR) and 20% recycled asphalt pavement (RAP) as one aspect of the warm-mix asphalt (WMA) project.

Jackson took infrared images of the project to double-check consistency of mat temperatures and confirmed that consistency coming from the plant to the jobsite.

“It was a balanced mix design, performance spec, SP095C (9.5-millimeter,) Superpave with ground tire rubber and RAP, warm mix, placed through a spray paver, and bonding to a concrete pavement,” he said. He listed off all those moving parts of the project like it was business-as-usual for the production and paving personnel. For a team that’s been on the scene since 1956, it almost is a walk in the park, yet they pulled out the quality control/quality assurance (QC/QA) and safety best practices to make sure everything flowed smoothly for an award-worthy project. In the end, they garnered the Missouri Asphalt Pavement Association (MAPA) 2023 award for a primary route under 50,000 tons. Here’s how they accomplished it.

Familiar Parameters

In 2012, NB West had successfully performed a project bonding an asphalt layer to concrete with the company’s Roadtec spray paver, and saw an opportunity to apply that technology again. Jackson explained the DOT originally was letting the project with the 19.0 mm mix and a 12.5 mm mix for the surface layer, but his team wasn’t excited about that because both layers would have been placed at less than four times the nominal maximum aggregate size.

“The thickness of the layer didn’t allow for the 12.5 mm to work smoothly,” he said. “In 2012, we’d done something similar bonding concrete with the spray paver, so after we were awarded the [Maries County] job, we did a value engineering proposal to bond to the concrete. We suggested two lifts of 9.5 mm Superpave with an overall reduction of 1 inch in the overlay. We’ve been trying to get back to realistic lift thicknesses that can get good compaction and DOT agreed with that.

The Relationship Between EPDs, BMD, RAP & Plastic

“We also proposed using ground tire rubber to delay the cracking coming back through the mix. The other reason for the GTR is we were doing our performance tests, and when we’re using the GTR in those mixes, our IDEAL-CT numbers have just been off the charts. Our performance tests are the IDEAL-CT and the IDEAL-RT.”

Good Numbers: For the Maries County project, the team saw an average CT-Index of 168, an average RT-Index of 77 and Hamburg rutting result of 7.0 mm.

The unconfined joints were on the outer edge of a concrete roadway that had a rock shoulder. The NB West crew paved the mainline and used a non-Superpave asphalt layer over the rock to cover up the shoulder.

Making Mix

Jackson credits the elasticity of the GTR for aiding in pavement performance. “We’re putting the ingredients back in that gives it a little flexibility.”

To add the GTR, NB West uses the dry process, adding Elastiko® engineered crumb rubber asphalt (ECR) manufactured by Envirotx and supplied by Asphalt Plus. N.B. West’s Joe Schroer, P.E., materials and support engineer, explained the dry process is considered mixture modification. Performance testing measures the interaction of GTR, aggregates and binder as a system, and allows a more innovative approach to designing asphalt mixtures, he shared. Additional enhancements to mixture performance can be made by adjusting the grade of the binder.

A groundman brings the 2,000-pound tote of Elastiko material to the feed bin of a modified Hi-Tech Fiber machine with a forklift. From the bin, the machine feeds the material to a 6-inch-diameter flexible hose and to the portable Astec Double Barrel.

Balance Your Mix Design for Asphalt

“We blow it right into the drum,” Jackson explained. “The control unit’s inside the control house and it’s tied into the tons per hour you’re producing.” In this manner, the plant controls the addition of the GTR product as it would cellulose fibers being fed in.

This project ended up with a variety of additives in the production process, but Jackson said it was business as usual for the team. “We had the normal challenges. This still had our normal Superpave testing in it; we were still running volumetric testing and adding in the performance testing. So, it was a lot of testing.”

Jackson shared a testing tip for working with GTR. “When you’re making pucks up, if you put a weight on your mold top (with the GTR in there), it keeps the GTR from rebounding while cooling. If you don’t do that, you get some kinda strange results.”

The unconfined joints were on the outer edge of a concrete roadway that had a rock shoulder. The NB West crew paved the mainline and used a non-Superpave asphalt layer over the rock to cover up the shoulder.

Smooth Quality

In the field, the crew worked with temperatures below 300 degrees F. Even with the Evotherm WMA additive in play, they elected to have temperatures closer to HMA to accommodate the Elastiko. “The manufacturer told us not to go below 280 with the GTR,” Jackson said. “We went down to 270 and didn’t have any problems.” A longer haul—approximately 40 minutes from the plant—for this project allowed a longer dwell time for interaction of the GTR with the binder at the reduced temperature, according to Schroer.

Jackson took infrared images of the project to double-check consistency of mat temperatures and confirmed that consistency coming from the plant to the jobsite. “I took my FLIR camera out there…the good thing is I think the ground tire rubber holds the heat in the mixes. It was about 40 minutes to the job, and we were on a two-lane road where we had to flag the traffic, so it was challenging getting the trucks in and out. But we didn’t lose a lot of heat in the mixes.”

One of the best practices Jackson recommended was staying on top of the rolling pattern. “We were keeping our rollers right up on the screed. Because we were already dropping our temps below 300.”

The mix design used all the moving parts. “We used 20% RAP in this mix and 10% by weight of AC was the asphalt plus Elastiko product. The idea was that we had our baseline AC, which was a 64-22 and 10% of the Elastiko was in there to bump it up to a 76-22. It was the same mix on both lifts.”

Is Your Lab Ready for Balanced Mix Design?

The Missouri DOT allows whatever percentage of RAP the contractor wishes to use and still meet performance specs. “Technically, there’s no limit,” Jackson said. “Our problem is availability. We can’t run maximum RAP in our mixes because we don’t have it. There was nothing to mill on this project, so we had to bring RAP from other locations to put in this mix.”

For the NB West team, that’s just one more solvable problem. Jackson spoke of the “can do” willingness to put a puzzle together when it comes to the crew, starting with Plant Operator Clay Pitts.

“Number One is just the general attitude of not saying ‘we can’t do that.’ Yeah, we’ll try that. That’s huge. Clay’s great about that. Always willing to try something new and make it work.

“Dustin Hollis was the foreman and Juan Marquez was the general superintendent; they manage several jobs at a time.”

Jackson also described the effort the quality control/quality assurance (QC/QA) team had to put forth, given the changes to the contract after it was bid.

“Our quality control dept came up with these mixes and tried new things and really kind of pushed the envelope. The performance testing, the way we did this, that wasn’t set up in the contract, so we still had to do all the volumetrics testing and add the performance on top in a BMD situation. We’ve never run this mix so we were going live on the road with what looked in the lab like it would run well and do its performance testing. We had to go behind the spray paver and dig a sample behind the screed in a mat that has a polymer in it. It was a monumental challenge for our QC team.

“We have our plant people and our QC people coming up with this crazy stuff and then we go execute it and we still have to make money at it. I think we did a slight tweak to the mix after the first day or two to take advantage of the performance test because we could reduce our air voids using the performance test.”

The final result gave an average international roughness index (IRI) of 32.

“On concrete pavement that they didn’t have enough pavement repairs for, to come out like that, I think it was great,” Jackson said.

Not only did the project win a MAPA award, the traveling public noticed the good work. Jackson has received unsolicited comments about the work. “I’ve had somebody call and say, ‘that rides real good.’ People see that [kind of result] and they’re more likely to support the gas tax.”

Balancing Mix for Optimum Density

One of the reasons NB West uses a warm-mix additive in every mix they can is to get the compaction aid assistance.

“We run Evotherm in every mix that we have to get density on,” Jackson said. “We don’t run it on Novachip, but every other mix, we’re putting it in there.”

One of the factors that changes when developing a balanced mix design (BMD) and doing your performance testing is the number of gyrations.

“You’re dropping your gyrations,” Jackson said. “You’re making a mix that’s got more AC in it. So, you can take advantage of some of those mixes then of making them more compactible in the lab so when you go to the field, it’s easier to get compaction.”

Take a typical interstate mix as an example.

“We started off at 125 gyrations on interstate mixes. When you’re trying to compact that, you’re breaking rock trying to get density. Then we backed off to 100 gyrations, then to 80. I think we’re at 60 with BMD.

“To keep your voids in mineral aggregate (VMA), you end up putting some more AC in it. So, you have a mix that will compact, and it’s got binder to hold it together. Now instead of breaking rock to get to 92%, you’re rolling this and getting 96%. That’s what FHWA wanted: higher density. We get higher density by going to balanced mix design.”

Learn More

Step 1: The forklift brings the tote of ground tire rubber product to the bin.

Step 2: The GTR product is fed through the 6-inch-diameter, flexible hose.

Step 3: The plant’s controls meter the product just as it would any cellulose fiber being fed to the Astec Double Barrel drum.

When P&S Paving Inc., Daytona Beach, Florida, was founded by Tim and Todd Phillips a little more than 30 years ago, the company had just one employee and one piece of equipment. The company’s three decades of operation have been marked by a number of milestones, from growing to employ more than 250 people and performing jobs valued at up to $75 million.

In 2023, P&S achieved another major milestone. The company was recognized with four Florida Pavement Excellence Awards from the Asphalt Contractors Association of Florida (ACAF). Not only was P&S awarded two special project awards and a third award for the best project in Florida’s District Five, but the company’s District Five project was also recognized with the A.P. Bolton Award for the Florida Road Builder of the Year.

The A.P. Bolton Award is ACAF’s highest award, named in honor of one of the association’s charter members with a reputation for high quality work. “A.P. Bolton was such an influential figure in our industry that it makes sense for him to be associated with the project that stood above all others in the state,” said P&S Quality Control Manager Tim Carter.

P&S Paving Warms Up Quality on I-95

The award-winning statewide project is selected from award-winning district projects, including new construction, reconstruction or major overlays on interstate or multi-lane primary highways requiring at least 30,000 tons of asphalt.

“This was the first time we’ve ever won a statewide award for any of our projects,” Carter said. “When they said our name at the ceremony, I almost couldn’t believe it. For a 250-employee company with just one asphalt plant to win that award out of all the fantastic paving companies in the state is amazing.”

The Florida Pavement Excellence Awards have been recognizing and honoring the best in pavement construction in the state of Florida since 1979.

All Eyes on I-4

One of the aspects of the I-4 project that stood out to P&S Paving was its proximity to the company’s asphalt plant just 10 miles from the project.

The A.P. Bolton Award-winning project stretched along 10.25 miles of Interstate 4 in Florida’s Volusia County, from west of County Road 4139 to State Road 44.

“I-4 is a highly traveled major artery that connects Tampa to Daytona,” Carter said, adding that it’s a common route not only for the transport of goods and services from one side of the state to the other but also for traffic to and from Florida’s theme park attractions. “Everybody in this area who goes anywhere and does anything, whether it’s work or weekend, travels on I-4.”

This, Carter added, includes many district and DOT employees. “It was a very high-profile project,” he said. It’s also along the route Carter travels to and from work each day. “Let me tell you, it was horrible. I couldn’t wait for it to be fixed. So, I was pretty excited when we won the contract to do it.”

According to Carter, the pavement had reached the end of its service life. “It had a rough texture, a lot of surface cracking, some rutting, loss of retroreflectivity of striping—those types of things,” he said.

The Florida Department of Transportation (FDOT) opted for full-depth repairs of a crack running the entire length of the project before milling and resurfacing the existing roadway, as well as pavement widening and improved traffic signalization.

This Too Shall Pass

“Mill and resurfacing was the most reasonable approach to rehabilitate this roadway,” Carter said. But before the road could be resurfaced, P&S had to repair that crack. “When the road was widened years ago, the joint between the existing pavement and the widened section turned into a huge crack running for miles in both directions. There had been some attempts to patch along some of the crack to try to mitigate further damage, but the patching was almost as bad as the crack itself.”

To repair the crack, P&S milled 2 feet on either side of the crack to a depth of 8 inches a full 10.25 miles and paved back two 3-inch lifts and one 2-inch lift of asphalt before milling and resurfacing the entire stretch of roadway.

“When we bid on the job, the first thing that caught my eye was its proximity to the plant—less than 10 miles,” Carter said. The second thing that caught his eye was the crack. Several years ago, P&S performed a very similar job on an adjacent section of I-4 in Volusia County.

“With the success of the previous project, I think that gave the department confidence to utilize that process again,” Carter said, adding that P&S’s past experience gave the company an edge over other bids. “We had already done something similar on I-4, so we knew we were capable of it, equipped for it, and had the knowledge and experience to perform that job.”

Time to Trench

The I-4 project required P&S to mill a 4-foot-wide trench along a crack running the length of the project. To introduce material into the trench, P&S devised and fabricated an attachment for the front of a skid steer that would feed material down into the trench. Prior to the I-4 project, P&S milled and filled a 4-foot trench at its main office to test and tweak the device.

P&S bid the project in 2020, began construction Nov. 21, 2021, and completed the project Nov. 13, 2022. The first 42 days on the project were devoted exclusively to the trench repair along the crack.

“When you’re paving a trench, you have to take your time,” Carter said. You also need to have the right equipment, he added. This includes a 4-foot milling machine, a 4-foot roller and some kind of device to get material into the trench. “If you have the right equipment and you take your time to get it right, by the time you’re ready to pave, you’ll have a solid base on which to pave.”

To introduce material into the trench, P&S devised and fabricated an attachment for the front of a skid steer that would feed material down into the trench. “There was nothing on the market we could buy off the shelf, so we had to bring everyone together to brainstorm and make our own.”

P&S Paving Puts Down Dry Process Plastics Pilot

To test and tweak the device, P&S milled and filled a 4-foot trench at its main office. “Once we got the device right, we invited the DOT officials out to the plant to demonstrate how we planned to execute the project,” Carter said. “Not only did that illustrate the spirit of partnership we have with the DOT, but it also put everyone’s minds at ease before we got out to the project.”

According to Carter, this quick ability to problem solve is where P&S’s smaller size is an asset. “It’s easier to create a culture of communication and innovation in a smaller company,” he said. “There’s not a lot of red tape if you need to get something done. If we need to order something, we order it. If we need to make something, we make it.”

The I-4 project required P&S to mill a 4-foot-wide trench along a crack running the length of the project. To introduce material into the trench, P&S devised and fabricated an attachment for the front of a skid steer that would feed material down into the trench. Prior to the I-4 project, P&S milled and filled a 4-foot trench at its main office to test and tweak the device.

Once the trench was milled out and refilled, P&S milled the entire span of pavement (including the new trench) before resurfacing. “Some of the repair efforts of the trench were sacrificed to make a smooth ride all the way across the pavement so you’d never know there was a repair underneath,” Carter said.

“Other than the trench, this was a fairly standard mill and resurface project,” Carter said. “That said, there are some basic tenets that go along with any successful mill and resurface project.”

Among these best practices, Carter stresses the importance of taking time to mill properly. “A smooth ride doesn’t start at the top, it starts at the bottom,” he said. Consistency is key, from keeping a consistent milling speed to a consistent flow of trucks and a consistent paving speed.  “If you limit the amount of times the paver has to stop then you will limit the possibility of bumps and joint issues.”

This also requires consistency at the plant. “The best way to keep your paver moving is to control your trucking and keep your plant production rates consistent,” he said. “And the best way to make consistent mix is to consistently make it; don’t stop and start and stop and start.”

Paving Weather

In total, the I-4 project required 58,000 tons of asphalt: 48,000 tons of Superpave 12.5 mm Traffic Level D HMA for the trench and 1 ½-inch surface course (with PG76-22 polymer modified AC) and 10,000 tons of open graded friction course (OGFC) FC5 HMA with PG76-22 for the ¾-inch friction course.

In total, the I-4 project required 58,000 tons of asphalt: 48,000 tons of Superpave 12.5 mm Traffic Level D HMA for the trench and 1 ½-inch surface course (with PG76-22 polymer modified AC) and 10,000 tons of open graded friction course (OGFC) FC5 HMA with PG76-22 for the ¾-inch friction course.

“Whenever you’re making OGFC in the winter, it’s a challenge—even in central Florida,” Carter said. The I-4 project had to be paved at night and FC-5 HMA has a minimum laydown temperature of 65 degrees Fahrenheit in Florida. “We can often get down below that between midnight and 5 a.m.”

Carter’s decision to use a warm mix additive in all of its mixes, including hot mix, was particularly useful for this project. “We don’t necessarily make warm mix designs with them, but we use Ingevity’s Evotherm product in everything, typically as a compaction aid,” Carter said. This means that even when placing HMA, the asphalt is workable at lower temperatures than it would otherwise be.

P&S also uses Evotherm as its anti-strip additive. “Everyone here is required to use a liquid anti-strip in all mixes, so it doubles to fill that role,” Carter said. “Why wouldn’t I use a product that also allows me more compaction at lower temperature without having to do anything differently?”

FDOT allows FC-5 to be placed at 60 degrees Fahrenheit when approved by the engineer, based on the contractor’s demonstrated ability to achieve satisfactory surface texture and appearance. For mixes containing PG76-22, the minimum average temperature may be further reduced to 55 when using a warm mix technology, if agreed to by both the engineer and the contractor.

“We were able to use Evotherm to our advantage to meet our production goals and avoid the loss of production days due to weather,” Carter said. “And the results speak for themselves.”

Hat Trick

According to Carter, P&S scored very well on mix production for the I-4 project. “We did well in all three categories; it’s a great looking project, it rides great, and it paid well,” he said.

Even before P&S won the A.P. Bolton Award, the I-4 project was a success. “We had a lot of district folks call up to let us know we were doing a great job on I-4,” Carter said. “I can’t tell you how many people called to tell us how good it looked, how well it rides, that we did a great job. That speaks volumes to the quality.”

The judges for the Florida Pavement Excellence Awards—including both FDOT district employees and ACAF staff—must have agreed. Projects are judged based on a number of factors, including technical scores for mix production, rideability score from a profiler test, and a visual score.

“The judges ride each lane of the road to check joint construction, edge of pavement, texture and surface anomalies, etc.,” Carter said. “The joints on our I-4 project are practically indiscernible, the texture of the OGFC was super consistent, the lane lines are symmetrical. It looks like we laid out that asphalt mat like a black carpet.”

But appearance wasn’t the only area in which the I-4 project scored well. It also achieved an International Roughness Index (IRI) of 31—the best IRI score P&S has ever received. “Most highways like this score anywhere in the 40-50 range,” Carter said. “That 31 isn’t the lowest score in the state, but it’s among the lowest. I think that’s what pushed us over the edge to win the statewide award over some of the bigger contractors in the state who had really constructed some outstanding projects that same year.”

P&S also received bonus composite pay factors for the surface level and friction course. “We scored very well on mix production here at the plant and on our densities, and we got incentives for those as well,” Carter said. “We did well in all three categories; it’s a great looking project, it rides great, and it paid well.”

Carter attributes the smoothness to the expertise of the crew to use the automatics on its Roadtec RP190 paver. “The pavement equipment is naturally a big part of that, but having the expertise and the skill to use the automated electronics is key,” Carter said. “It’s one thing to have them, but it’s another thing to know how to use them and use them well. If you can use automatics well, this is what you get.”

P&S has established a training process to ensure its crew knows how to best utilize the automatics on its equipment. The company regularly sends its mechanics and paving crews to Roadtec’s training program in Chattanooga, Tennessee.

“Success comes down to discipline,” Carter said. “Do you keep your folks well trained, your equipment in good working order, and your morale high?” Keeping morale high, he adds, includes ensuring every employee feels as though their opinions matter, their good work is appreciated, and they are full participants in their employers’ victories.

“When we won these awards, we really shared that victory with everybody,” Carter said. “When we received the incentives from the ride bonus, the owner chose not to pocket that money but instead shared it with all the people involved in that project because they did such a great job. I’ve never worked anywhere where someone did that.”

Carter said everyone at P&S was at peak performance on the I-4 project, but that the company’s success isn’t a matter of performing on one single job. “Our guys perform every single day,” he said. “Not once or twice a week, but all five days of the workweek, week after week. That’s the real trick. Anybody can do something well once, but can you repeat that over and over again?”

Smoother AND Safer

The I-4 project also included widening of the shoulders. “If you drive around Florida, you’ll see that many of our shoulders are up to 10 feet wide,” Carter said, adding that FDOT has been adding that to many contracts in the past few years. “The DOT makes extensive use of the Road Ranger program, and they want to make sure these contracts are designed to maximize safety for those guys out there helping motorists.”

An intelligent transportation system (ITS) was installed at the intersection of State Route 44, another major corridor that runs north-south through Volusia County. “The Volusia County Fairgrounds are about 1/4 mile from that intersection, and there’s a lot of activity at the fairgrounds throughout the year, so they upgraded the traffic signals to make traffic there more efficient and safer,” Carter said.

“Ultimately, this project enabled FDOT to repair that crack while giving this piece of roadway some new life with the resurfacing part of the project while also improving safety by widening the shoulders and adding some signalization to improve traffic flow.”

Three Projects, Four Awards

Caption: Space Coast Regional Airport is the nearest airport to Kennedy Space Center, one of the 10 field centers belonging to the National Aeronautics and Space Administration (NASA).

In addition to the two awards P&S received for its I-4 project, the company also received two Florida Pavement Excellence Awards in the special projects category. One of the awards was for the milling and resurfacing of runway nine at Space Coast Regional Airport.

“It’s a really old regional airport, so the project wasn’t without its challenges,” Carter said. P&S used machine control guidance through the milling phase to get the proper cross sections, then placed the P401 wearing course.

The second project for which P&S received a special projects award was the reconstruction of the running track at Embry Riddle Aeronautical University in Daytona, a world-renowned aviation school.

“They have a pretty robust sports program there at the university and host international track and field events,” Carter said. P&S was chosen to full-depth mill the oval running track and pave back 1 ¼ inches before the specialty contractor could come out to apply a rubberized surface course.

“The paving of the underlying asphalt is key for the specialty contractor who will be placing the rubberized materials on top,” Carter said, given the tight specs they must meet to ensure no competitors are given an unfair advantage. “When the paving is done, these guys typically have to grind out some areas and fill in other areas. The more of that they have to do, the worse the paving job was.”

After the track was completed, P&S received a letter from the specialty contractor’s field superintendent that said, in his opinion, “the work by P&S couldn’t have gone better. In fact, it was probably the best paving job I’ve seen in 10 years.”

The superintendent told Carter they sometimes use 25 to 35 barrels of filler material to even out the pavement, but this job required only two and very minor grinding. “That goes back to the discipline that our guys use when they’re paving these high spec projects,” Carter said.

Researchers have established that longitudinal joint performance influences the lifespan of a pavement. If the joint is built with higher permeability and lower density compared to the rest of the pavement, water and air intrusion leads to accelerated damage, which often requires maintenance within three to five years.

This graphic shows the timeline for PennDOT’s road to a standard special provision for void reducing asphalt membrane use. All images courtesy of Associated Asphalt

Over the years, multiple agencies have investigated various strategies to enhance the performance of asphalt pavement longitudinal joints. Despite these efforts, high permeability remains a challenge. The void-reducing asphalt membrane (VRAM) has demonstrated its effectiveness as a solution that prolongs the life of longitudinal joints.

VRAM is a material-based solution involving the application of a thick layer of hot-applied, polymer-modified asphalt (PMA), rather than an emulsion. It is applied beneath the future centerline of the longitudinal joint. As hot-mix asphalt (HMA) is laid and subjected to heat and compaction by rollers, the VRAM gradually migrates from the bottom up, rendering the joint nearly impermeable to water and air. The VRAM “wicks” upward in the longitudinal joint area during paving, essentially filling the air voids remaining in the longitudinal construction joint.

Check out the January 2019 Here’s How it Works for a step-by-step guide to creating a joint with VRAM. Read the March 2021 “Innovate at Centerline Rumble Strips” for additional information on the membrane’s use.

Initial trials for VRAM occurred in Illinois in 2001 and 2002. In 2017, follow-up testing and observations by the Illinois Department of Transportation (IDOT) revealed the experimental sections exhibited lower permeability and higher asphalt content compared to the control sections, resulting in improved crack resistance.

In 2018, the Pennsylvania Department of Transportation (PennDOT) developed a work plan to investigate VRAM via 14 trials via a five-year period. One of the VRAM products selected for these trials was J-Band® and that’s what we’ll look at here.

Asphalt Materials’ J-Band® Void Reducing Asphalt Membrane

First PennDOT Trial

PennDOT District 5 began its first trial on a 2.1-mile stretch of I-81 in Schuylkill County in October 2018. Annual visual assessments were conducted to examine the state of the VRAM longitudinal joint and the control joint.

In April 2023, Dave Powers, Associated Asphalt’s Northern Region performance products manager, along with representatives from PennDOT Central Office, District 9 and District 5, carried out a fifth-year evaluation.

In the VRAM experimental section, in line with expectations for the fifth year, they observed minor cracks present on the joint’s surface in a few areas. However, these cracks did not penetrate into the paving mat. The majority of the experimental section remained devoid of cracks.

In the control sections built with traditional joint methods, they observed the project faced issues stemming from underdrain and material failures. The northbound control area underwent milling and replacement in July/August 2019, which is nine to 10 months after the trial began. Nonetheless, District 5 managed to avert the replacement of the experimental VRAM section. Instead, the new joint installed in 2019 was treated as the “control joint” for this pilot project. Despite the control section being paved subsequent to the experimental joint, the VRAM continued to demonstrate superior performance.

Innovate at Centerline Rumble Strips

Second PennDOT Trial

PennDOT’s second VRAM trial was applied Oct. 17, 2018, on a 1.1-mile section of I-380 in Monroe County. This experimental section would be compared over time to approximately 0.5 miles of control sections.

A team visually reviewed the joints annually, and in 2021, cores were pulled from the 3-year-old joints in the control and VRAM sections. These cores were sent to Rutgers University Center for Advanced Infrastructure & Transportation (CAIT) for complete testing. While the annual visual inspections did not reveal substantial differences between the control and VRAM sections, the lab data showed differences in favor of VRAM.

Air Void Determination—The air void determination indicated that the control section had higher air voids than the VRAM section for the 9.5-mm SMA surface course with the butt joint longitudinal joint construction (10.4% vs 8.2%, respectively).

Falling Head Permeability (FM 5-565)—The application of the J-Band product significantly reduced the permeability of the compacted asphalt at the longitudinal joint. On average, the permeability of the J-Band-treated longitudinal joint was approximately 35 times slower than the conventional longitudinal joint. When permeability testing was conducted using the entire core provided (9.5-mm SMA plus J-Band plus binder course), the VRAM sections were determined to be impermeable, indicating the VRAM seals off the underlying asphalt layers below the longitudinal joint area.

IDEAL-CT Index—The application of the J-Band product significantly improved the cracking resistance of the longitudinal joint as determined using the IDEAL-CT Index test procedure. The application of the VRAM product increased the IDEAL-CT Index of the longitudinal joint by almost 4 times compared to the IDEAL-CT Index values measured in the control cores.

All trial cores for PennDOT resulted in these average IDEAL-CT Index scores. Graph courtesy of Associated Asphalt

Another visual inspection was completed in December 2022. The VRAM joint continued to show less cracking than the control joint.

Through the end of 2022, thirteen trials had been constructed, including four in District 5, two in District 4, and one each in Districts 1, 2, 3, 6, 8, 11 and 12. In total, six separate core tests were conducted, including the 3-year-old joints pulled from the second trial described above. The graphs included here summarize some of the data collected from the PennDOT test project by Rutgers University CAIT. Overall, VRAM effectively demonstrated an improvement in IDEAL-CT (crack resistance), as well as a reduction in permeability. VRAM improved the performance of the asphalt pavement mat at the longitudinal joints by reducing permeability and lowering air void content.

All trial cores for PennDOT showed these average air void percentage results. Graph courtesy of Associated Asphalt

New VRAM Standard Special Provision

In March 2023, PennDOT issued a new Standard Special Provision for Void Reducing Asphalt Membrane (VRAM). This SSP, which can be used on projects let on or after April 14, 2023, is recommended for use on limited access and expressway-type pavements where exceptional longitudinal joint performance is difficult to achieve. An added benefit of using the VRAM SSP is the joint density specification does not apply. As of August 2023, there have been six VRAM projects completed or scheduled to be completed in 2023, and seven confirmed for 2024.

When trying to increase the life of the mat, notch wedge joints (NWJ) are a superior alternative to butt joints. Since it is not always possible to run hot echelon paving, contractors can use the overlap of a notch wedge joint to increase the density of the longitudinal joint thus increasing the life of what traditionally seems to be the first failure point in paving. For example, we see an average of a three points increase in joint density when building with our notch wedge device versus a butt joint.

There are two predominant types of notch wedge devices right now:

• devices that go inside the screed
• devices that are attached to the outside of the endgate

We prefer the efficiency of the on-and-off devices that attach outside the endgate, such as our Willow Notch Wedge device, so when referring to devices in this article, we will be referencing the ones pictured here. Simply put, the mechanic can attach a bracket to be left on the screed or use the simple bolts on the device that allow for in-field attachment and removal in a few minutes.

These devices are offered by Willow Designs, East Berlin, Pennsylvania. Jerod Willow, the proprietor, took the time to prepare this step-by-step guide for building a successful notch wedge joint for the 2024 Training Directory.

Depending on the climate and quality of the mix, there are also options to add heat and/or vibration compaction with devices. Additionally, many companies choose to also use a specialized pneumatic roller from Willow Designs that attaches via a hand twist bolt to the notch wedge device alleviating the need to roll the wedge portion with an additional machine.

The Willow Designs notch wedge device affixes outside the endgate.

This pneumatic roller adds compression to the vertical joint while reducing raveling and fracturing of aggregate at the wedge. When used in tandem with the pneumatic roller, we see joint densities increase by an average of four to seven points.

For the first-time use of the Willow notch wedge device and pneumatic roller, I provide a shift of support to the paving crews so that they can achieve the best numbers with the product the conditions will allow. Often a full shift is not necessary due to the ease of use, but once in a while the team takes advantage of all my experience and they dig into the weeds of best paving practices.

When a contractor purchases the notch wedge device and pneumatic roller, the paving crew receives a shift of support to help them understand how to affix it to the endgate, how to use it, how to pave and compact the joint properly, and so on, to achieve the best numbers with the product that conditions will allow. Notice in the second image that the breakdown roller is rolling the first pass with the steel drum overhanging the joint. The Willow Designs team has found the breakdown roller should be rolling as soon as it can fit behind the paver, compacting as hot as possible and overhanging the joint by 12-18 inches of drum. All photos courtesy of Willow Designs

Here is the step-by-step process to build a notch wedge joint.

Step 1: Select your system of choice and affix it to the endgate.

Based on your paver’s screed type, a simple bracket can be bolted to the endgate that the device can then be attached to. The device could also be directly bolted to the endgate.

The pneumatic roller is attached with a T-bolt to a stud on the notch wedge device. The release agent container is filled and snaps into brackets on the mat side of the roller.

When a contractor purchases the notch wedge device and pneumatic roller, the paving crew receives a shift of support to help them understand how to affix it to the endgate, how to use it, how to pave and compact the joint properly, and so on, to achieve the best numbers with the product that conditions will allow. Notice in the second image that the breakdown roller is rolling the first pass with the steel drum overhanging the joint. The Willow Designs team has found the breakdown roller should be rolling as soon as it can fit behind the paver, compacting as hot as possible and overhanging the joint by 12-18 inches of drum. All photos courtesy of Willow Designs

Step 2: Apply tack.

Some states are now requiring that a longitudinal joint sealant (LJS) or void reducing asphalt membrane (VRAM), such as the J-Band product from Asphalt Materials Inc., be applied along the centerline. Check with your state specifications.

Step 3: Pave the first pass.

This is the time to dial in the device according to the mix and specifications of the job.

The primary jack is used to lower the inside portion of the device’s screed for the depth of the vertical notch. Bear in mind that you need to add the compaction depth of the mix to the depth of the vertical notch. We try to set the notch of the device at 40% above the compacted mat thickness while also trying to accommodate the largest aggregate in the mix.

Here you see the primary jack and turnbuckle highlighted.

Once the depth is set, use the turnbuckle which adjusts the slope of the wedge/toe slope/outside portion of the device’s screed. Also, the toe of the slope on the wedge should not be less than a stone’s thickness, otherwise there could be segregation in the wedge mat. Most states specify a 12-inch width of wedge, but the Maine DOT is playing with a 6-inch wedge for lift thicknesses that are less than 2 inches.

• Some devices have vibratory options, and during this step, you would turn on the vibration to the setting of your choice.
• With cold weather climates and SMA mixes, the heated screed plate would be plugged in before paving and then shut off once the device is running hot mix.

If the pneumatic roller is being used, then this is also the time to generously add release agent to the roller via the attached spray tank and nozzle. Release agent needs to be maintained until the roller heats up and then less material is required. Adjust the turnbuckle on the mat side to adjust the lateral tracking to just overlap the vertical edge by 0.5 or 1 inch.

The paver lays the second pass against the vertical edge and overlaps the wedge. Be careful to match the joint at the proper elevation so as not to starve the joint for asphalt mix.

Step 4: Roll the first lane.

This we find is probably the number one improvement to be made in low joint density numbers for compaction of the first lane with an open wedge joint. The breakdown roller should be rolling as soon as it can fit behind the paver, compacting as hot as possible. The rolling allows for the roller to overhang the joint by 12-18 inches of drum over the wedge. It does not seem to matter if it is rolled first or last in the pattern. We always recommend using the extra pass (if there is one) in a pattern on the open joint. This applies to all steel drum rollers in the paving train.

We have found that running another method of compaction on the 12 inches of wedge is not necessary if the Willow pneumatic roller was used initially.

As mentioned in Step 1, release agent is used for the pneumatic roller compacting the wedge immediately behind the screed. Keep in mind, the release agent is applied liberally at the beginning of the operation but is required in smaller amounts as the roller heats up.

Step 5: Apply tack to the second lane.

Spray the wedge with a double application in addition to coating the second lane. If there are any voids in the mat of the notch wedge joint, the heavy tack coat application will fill these and actually increase your chances of achieving higher joint density numbers.

Step 6: Lay the second lane.

The paver lays the second pass against the vertical edge and overlaps the wedge. Be careful to match the joint at the proper elevation so as not to starve the joint for asphalt mix. Longitudinal joints that are matched low will ultimately produce low joint density numbers because the compaction train will bridge on the cold lane of pavement being matched. We often see screed operators do this because they have been taught to build an “invisible joint” that rolls in clean with less distinction. We now know this is a failed joint waiting to happen. We can check good joint elevation by depth-checking proper loose depth thickness of the pavement at the matched joint 14 inches into the hot mat. The wedge will then heat back up and become the second lane as shown by joint density cores.

Cores should be centered over top of the wedge, which is roughly 3 inches from the seam. That provides the best representation of the joint.

The paver lays the second pass against the vertical edge and overlaps the wedge. Be careful to match the joint at the proper elevation so as not to starve the joint for asphalt mix.

Step 7: Roll the second lane.

Based on project conditions, for the breakdown, stay 12 to 14 inches off the matched joint with the first pass toward the paver. For the second pass, steer the roller to where the drum has a 12- to 18-inch overhang onto the cold lane. Not all job conditions allow for a great overhang, but the best results from our testing show that an 18-inch overhang puts the weight of the roller directly over the joint. This compacts the material into the joint, stabilizing the mix over the wedge. Then you continue rolling the mat as normal. We always recommend if there is an extra pass in the pattern to put it over the joint.

If specified density is not being achieved with this equipment, we need to dig deeper into good paving practices.

Jerod Willow is the proprietor of Willow Designs, East Berlin, Pennsylvania, and has over 20 years experience in the asphalt and paving industry. He saw a chance to improve asphalt life by developing user-friendly devices to meet the needs of contractors. He also uses this knowledge to teach paving classes and does onsite training as well as consulting for companies looking to improve their paving practices. For more information, contact him at (717) 919-9828.

Preferred Materials Inc., a CRH company based in Tampa, has a host of quality in construction (QIC) project wins to its name, but there’s a pair of projects along Interstate 75 (I-75) in Florida that deserves extra attention. Let’s start with the one you can find between exits 254 and 256, which crews returned to traffic Oct. 12, 2021.

The company took home a QIC award from the National Asphalt Pavement Association (NAPA) in January 2022 for this project of over 50,000 tons. The mill-and-fill encompassed eight total lanes north of CR672 to south of Progress Blvd. on SR93A/I-75 where the company placed a surface mix of FC5 Superpave mix design. The crew first milled and replaced 2 inches compacted of structural course, then placed the open-graded friction course (OGFC) at a mere ¾ of an inch, yet they achieved something remarkable—an average international roughness index (IRI) on the project of 25.

What’s more remarkable than that? The same crew performed the same mill-and-fill work with the same mixes immediately south of the 8-mile project in 2020 with an average IRI of only 24.

Farhad Zafaranian, E.I., M.S., is the construction manager for Florida Department of Transportation (FDOT), Tampa Operations Center, and shared this represents the “[s]moothest pavement in the history of FDOT since IRI has been recorded. It is important to note that the low IRI number would reflect consistency in production as well as placement procedures, which is the ideal goal of FDOT’s quality control process.”

“As both the state construction pavement engineer and a road user, I’m very happy to see our roads getting smoother than ever before,” said FDOT’s Richard M. Hewitt, P.E. “I believe it is a direct result of the department’s incentive/disincentive smoothness specifications and a contractor who has put effort into trying to pave smoother than ever before. I’m very proud of the work Preferred Materials achieved on their two I-75 projects, as well as the majority of our asphalt paving contractors who have been paving significantly smoother in recent years.”

That pride is shared. Richard Crocker, operations manager of Preferred Materials Asphalt Division Tampa, wore his commemorative “24-IRI Club” polo shirt during our interview at CONEXPO-CON/AGG and spoke readily of his team’s accomplishments. He proudly named the foremen and roller operators who contributed to the success of the 24-IRI project and easily spoke about their skills, not only on the I-75 projects, but also on a recent racetrack project that took all hands on deck.

“A year-and-a-half later, we went up and did another project just north of it and repeated the same,” Crocker said. “That same crew with the same rollers, with the same operators. And this is why you must take care of your people. You don’t want your people coming and going and losing their expertise.”

The secret to success is working with skilled operators who know their best practices and know their equipment. “Try to keep people on the same piece of equipment as often as you can,” Crocker said. He advised the successful companies out there will crosstrain crewmembers and have multiple workers who can perform the vital tasks on the paving train, but you’re building a team of experts.

Pat Longstreet is the foreman for the crew that handled the I-75 project and his breakdown roller operator is Javier Gonzalez, who has 14 years with Preferred Materials. He runs a Sakai in the breakdown position and typically runs it with both drums in oscillation mode.

“For I-75, for the structural mix, we were putting down about 900 to 1,000 tons per shift due to lane closure restrictions,” Crocker said. The team performed layout and milling, so they had about six hours of paving before they had to turn things over to striping and open it up to traffic. “We were paving at about 28 to 32 feet per minute on the structural on 75 at 12 feet wide, 2 inches compacted.”

Collaboration Across the Board

Charles Holzschuher, P.E., is the state pavement materials engineer for FDOT. He spoke of attaining smoothness as a collaboration: “Based on collaboration with industry and the department, roadway construction and implementation of these smoothness specifications has improved the quality of paving resulting in smoother IRI. Ultimately, the goal of smoother pavements and utilizing industry leading construction techniques is to embrace innovation, technology, and competition which has resulted in smoother pavements on a statewide level.”

While FDOT isn’t going to dictate a specific technology, the one Crocker spoke of as integral to smoothness success during our time at CONEXPO was oscillation for compaction.

Good Density Equals Smoothness Bonus

The crews use rollers from Sakai, as mentioned above, and they typically have them set in oscillation mode, according to Crocker. It’s a feature of Sakai rollers that the front and back drums can be set in either vibratory or oscillation mode, or be switched from one mode to the other, or be both in oscillation mode.

“I like the capabilities of both drums being able to oscillate,” Crocker said. “Very seldom do we oscillate with only one drum. 99% of the time, we are oscillating with both drums. We do use the vibration on the 750 pneumatics, too. That’s usually on a #3 or #4 setting, whether we’re putting out a poly mix or not, we use them. And, again, that’s training roller operators and setting expectations and knowing what to do.”

While at the booth at CONEXPO, attendees could gather information about the benefits of mixing and matching technologies. Studies showed using both drums in oscillation mode offered bonus potential; check out the sidebar below for that information.

Crocker also spoke of the importance of collaboration and cooperation with all the partners and owners. By communicating needs and requests up front, contractors increase their opportunities to use best practices. They increase their chances to achieve the smooth results the asphalt industry can offer the taxpayers.

“We try to do a lot of continuous paving and that’s why we get the IRI result numbers we do,” Crocker said. “We coordinate, we plan, and we execute. There are a lot of partners that go along with that. Trucking, traffic control, the plant, QC, milling, cleanup.”

Crocker explained that the plant might be producing 4,000 tons of FOB mix on a given day, but his crew needs to pull 1,000 tons of structural. That takes coordination. Planning. A dedicated group of silos and one lane of the scales that the truckers know they’re to access.

Simon Wins for Smoothness on SH-14

“It’s all relative,” Crocker said. “If we can continuously pave, then we can continuously roll.”

One way to increase the time spent paving is to ask for it. If you have a good reputation, you might get that time. For example, he said the I-75 projects had clear start times at 10 p.m. and stop times before rush hour traffic kicked in. “You had to be off the road, and that’s painted, everything’s off the road by 6, some spots of the road was by 5.”

What Crocker shared is how to wisely extend that time. “If you can go out and show, hey listen, over this 12 miles, I can eliminate four sets of transverse joints,” you could gain “an hour or an hour and a half at the beginning of the shift.”

He explained that you can approach the project owner, even if that’s a DOT with set specs for the project, and show them what you can do with the extended time. By eliminating transverse joints, you eliminate the potential for bumps in the road. By extending time on the northbound lanes while most traffic is building up southbound, you’re using time wisely.

“You gain an hour, hour and a half at the beginning of the shift going northbound because all the traffic then is trying to go south,” Crocker said. “Then when you go the other way, you get it on the other end.”

Quality, Smoothness and Speed to Completion in Colorado

Crocker said you must then execute what you say you will, or the agencies won’t be eager to grant requests in the future. That means instilling pride in workmanship in your crewmembers and getting quality results that back up what you say you’ll do.

“We try to empower all of our people from the guy putting out the cones all the way up to our VP,” Crocker said. “We try to empower our people to take pride. Our reputation has got to get us something. And it has. We have a great safety record, and we have the smoothest road in the history of Florida DOT.

“And this is worth talking about; you have to back up what you say. With our equipment, with our rollers, I was confident we were going to get joint density, I was confident we were going to get mat density, and I was confident we were going to get ride.”

Asking for what your crew needs helped Preferred Materials get the recent racetrack paved in an efficient manner as well. Crocker explained they worked with the owner to gain access to the site for continuous paving. “We had to talk to the (track) owner about access, about ingress and egress because they had the guardrail up. There’s only so much opportunity to get in on a racetrack.”

As Crocker said above, the team coordinates, plans and executes the plan. For the racetrack project, they wanted to eliminate any centerline joint, so they made a plan to build up, staggering and layering with echelon paving in mind. “We figured out which crew should be wider and which narrower to stagger the center joint.”

They placed the base with one paver and material transfer vehicle paving 17 feet wide; the other coming alongside at 13 feet wide to total the 30-foot width. When it was time to place the surface, they staggered differently. “For the friction course, the joint was right down the center.”

The racetrack crew also faced a temperature challenge with a high-polymer mix. It was produced at about 340 degrees but lost temperature in a hurry once it left the haul truck. “We had a 15-minute haul. By the time it was coming out the back of the screed, it was already down to 285, 290 degrees and that’s with 80-degree ambient temperatures in Florida.”

“We were only paving 18 to 20 feet per minute,” Crocker said. “We’re using automation on the paver. We’re using two non-contact skis. It’s a MOBA-based system. Your rollers are trying to roll this joint. The first roller has to stay off the joint. The second roller has to roll it over and push it down. The rollers are the key. We had to look at when do you start the breakdown process? In this case, immediately.” And the rollers had to come right up to the screed. “We had to communicate that in the pre-construction meeting.”

Solve Rideability at the Paver Track

Best practices came into play. “When the roller starts to approach, he has to come right up to the screed. We can’t stop 20 feet away, and we can’t stop straight. He has to always stop at an angle. And when we come onto the mat; we have transverse joints, we can’t come onto the mat straight, we have to come on at an angle.”

Pat Longstreet and his crew had Gonzalez as the breakdown roller operator on the racetrack project. Chris Longstreet and his crew were the second crew on the project. They had two breakdown roller operators during the project: Ceasar Jimenez, who has been with the company for eight years, and Mytara “Nubs” McCray, who has been with the company for 22 years.

That longevity, coupled with the skill and pride in workmanship so evident in the Preferred Materials ethos, lends itself to a set of low-IRI, high-quality pavements that our industry can point to as examples of exemplary asphalt construction. As the team at FDOT pointed out, getting high quality translates to long lasting pavements for the taxpayers, and that’s a win we can all be proud of.

Smoothness Matters

The Florida Department of Transportation (FDOT) has put time and energy into its smoothness specifications to encourage and reward those contractors who take on state projects. One of the measurements of smoothness is the International Roughness Index (IRI), which members of FDOT discuss here.

Farhad Zafaranian, E.I., M.S., Construction Manager, Tampa Operations Center: “IRI describes how much total vertical movement a standard passenger vehicle’s body would experience if driven over a 1-mile segment of the subject pavement at 50 mph. IRI is useful for assessing overall pavement ride quality; a higher IRI value indicates a rougher road surface. It is used by highway professionals throughout the world as a standard to quantify road surface roughness. A continuous profile along the road is measured and analyzed to summarize qualities of pavement surface deviations that impact vehicle suspension movement.

“Lower IRI equates to a smoother pavement surface which equates to increased pavement life and it will create a more pleasurable driving experience for the travelling public. Ultimately it would contribute to lower number of accidents, and decreased maintenance cost.”

Charles Holzschuher, P.E., State Pavement Materials Engineer: “Pavement smoothness is a key performance indicator and top priority for road users. Smooth-riding pavements provide comfort, raise optimum travel speeds, maintain traffic flow, reduce safety hazards, and increase fuel efficiency. Pavement smoothness also imparts a positive reflection on the construction and maintenance proficiency of the owner agency. Furthermore, research has shown that over time, smooth roads cost the owner/agency and users less in maintenance and lead to longer pavement service lives.

“To better achieve smooth pavements and increase the service life of our roads, FDOT in partnership with the paving industry has formed smoothness-based specifications to promote good construction practices and to develop and implement profile-based construction smoothness specifications. The long-term success of profiler-based specifications relies in part on the implementation of an FDOT profiler certification program to verify the accuracy and repeatability of test equipment to measure a longitudinal surface elevation profile.

“To realize this goal, a certification test track was constructed at Williston Municipal Airport. The test track meets the reference and inertial profile requirements set forth in AASHTO R-56. This certification program will ensure profiler operators have the ability to collect profile data and evaluate the quality of the acquired data.”

Richard M. Hewitt, P.E., State Construction Pavement Engineer: “Smoother pavements are not only more enjoyable to ride on, but they last longer and can help reduce some vehicle maintenance costs. Since smoother pavements last longer, the cost is spread out over a greater number of years resulting in a lower annual cost for pavement.

“The IRI provides a rating of the quality of a pavement’s ride with lower numbers representing smoother pavements and higher numbers representing rougher pavements. Lower IRI, i.e., smoother pavements, last longer and result in less maintenance costs for the state and for road users’ vehicles.

“Most drivers are not familiar with asphalt content, aggregate gradation, air voids, or density, but they do know if a pavement is smooth or not. As such, smoothness is the measure by which road users evaluate pavements.”

Let’s Oscillate

The team from Sakai set up an educational section of their booth at CONEXPO-CON/AGG 2023 where they displayed three slabs of SMA pavement, constructed using six passes of a breakdown roller moving at 3.4 miles per hour.

The first sample showed results of a Sakai SW994ND roller with both drums in vibratory mode at 3,000 VPM. The objective results showed an IRI of 99 (inch/mile), a theoretical maximum specific gravity (TMD) of 95.9% and MPD of 0.39. The summary suggested fair rideability and that “Vibe may reduce surface air void due to downward pressure.”

The second sample on display at the Sakai CONEXPO-CON/AGG 2023 booth showed results of a Sakai SW994ND with both drums in oscillation mode. Photo courtesy of AsphaltPro

The second sample showed results of a Sakai SW994ND roller with both drums in oscillation mode. The objective results showed an IRI of 50, a TMD of 97% and MPD of 0.61. The summary suggested this one’s IRI value fell in the FHWA’s “very good” rideability category; its highest MPD value of the three tested offered better draining and the quietest, safest ride; and that “Dual drum oscillation with reduced amplitude reduces scoring of binder content.”

The third sample showed results of a conventional roller with one drum in oscillation mode and one in static. The objective results showed an IRI of 174, a TMD of 97% and MPD of 0.42. The summary suggested this one’s IRI value fell in the FHWA’s “very poor” rideability category and that “Excessive oscillation amplitude in single drum scores aggregate/binder, reducing life.”