The asphalt professionals at Road Builders paved approximately 200 tons a day on a Waikiki mill-n-fill project amid heavy tourist traffic

Performing a pavement maintenance project in paradise may sound like a dream job, but it takes the same dedication from the crew and commitment to best practices that paving anywhere else in the world requires. In fact, the rehabilitation of Kalakaua Avenue on Waikiki also required strategic work zone setup and safety vigilance to keep foot-traffic off the fresh mat—a mat that met specs for the City & County of Honolulu Department of Design and Construction (DDC). Let’s take a look at how an experienced team from Road Builders Corporation, Honolulu, handled it all.

Project Manager Jennifer Gallego-Nakamoto shared the team worked together to ensure the project could “flow as we go,” with communication between crew members, foremen, engineer, superintendent, project manager, city inspector, safety officer, traffic control technicians and special duty officers. Operational Manager Mike Park said the company hired six Hawaii Police Department officers to assist in traffic control and used common courtesy as part of standard operating procedures. “You have to be humble,” Park said. “You can’t have arrogant people coming in. We have to be gentlemen,” he said of the way everyone carefully directed tourists around the site. “They did a great job out there.”

Hawaiian Project Specs

For the 2024 Rehabilitation of Streets, Unit 76A Kalakaua Avenue project, Road Builders milling and paving crews began in May, milling at a depth of 4 inches. The width, varying from 19 to 24 feet, depended on the lane structure. You see, Kalakaua is a four-lane thoroughfare with bike lanes along its ocean side and multiple four-way intersections with turn lanes. Mike Park, VP of operations, said “every day presented different challenges” even though every day the crew milled and paved back at least two lanes of an 800- to 1,000-foot section between 8:30 a.m. and 3:00 p.m.

To accomplish all this, they used a Wirtgen W 210 Fi cold planer and Astec’s Roadtec RP-195 10-foot tracked paver. Seven haul trucks delivered a State IV mix from the ADM EX 8844 Series plant located about an hour from the job site. Production averaged 160 to 180 tons per hour at a temperature of 330°F.

Back row, from left: Alani, Larry, Noah, Mana, Lewis, Johnny, Pana, Mike, Derek, Vinny. Front row, from left: Jennifer, Aaron, Jay, Edgar. This is the Road Builders paving crew that achieved paving and safety success along Kalakaua Ave. in the summer of 2024.

“Kawika Ishikawa has been in the asphalt industry for about 19 years and has worked as a plant operator for 16 of those 19 years,” Project Manager Jennifer Gallego-Nakamoto shared. “He currently is the plant manager/operator at Ala Imua LLC, which supplies the hot mix for Road Builders Corporation. We are fortunate to have him on our team. He’s not just the operator, he’s also our troubleshooter and will work tirelessly to find solutions whenever challenges arise. His expertise has been instrumental in continuing to keep our plant in operation.”

Paver Operator Aaron Manuel is a veteran asphalt industry professional as well. Gallego-Nakamoto shared Manuel “has worked in the asphalt industry for 16 years with 8 years as a paver operator with Road Builders.” She remarked that his positive, “do-whatever-I-have-to-do” attitude makes him a valuable part of the team.

As one of seven haul trucks brought State IV hot mix to the Roadtec RP-195 10-foot tracked paver, multiple Road Builders workers handled traffic control on the Kalakaua Ave. rehabilitation project. If you look closely, you can see one worker in PPE near the “top” of this photo drawing attention to a sandwich-board sign. A multitude of safety cones delineated the lengthy work area and yellow caution tape was tied to trees as one more “flag” to pedestrians to pay attention and prevent them walking into danger. Photo courtesy of Project Manager Jennifer Gallego-Nakamoto, who took a number of these photos from the rooftops of Outrigger Hotel and Waikiki Circle Hotel

Behind the paver, the team ran a SW654ND Sakai roller. The 8-ton roller with 58-inch drum achieved 91% compaction and a Sakai 5-ton roller took care of finishing and final compaction of 94%.

Gallego-Nakamoto explained they built transverse joints by trimming the cold joint each day, applying tack coat and paving into the edge of the joint. In fact, she spoke of the crew’s performance on the joints with pride. “Our crew did a good job with the transverse joints. Roller operator John Dorser thoroughly compacted the transverse joint, ensuring a smooth transition. John did a great job achieving his rolling pattern to reach the required compaction.”

The 4.5 lane miles of Kalakaua Ave. to be rehabilitated were between Olohana St. to Monsarrat Ave. and Dillingham Fountain to Poni Moi St. Currently there are four, one-way lanes that reduce to three lanes toward the end of the roadway. The avenue is the main thoroughfare to Waikiki connecting tourists to shops, restaurants, entertainment venues and, of course, the beach. “Originally it was called Waikiki Road, and later changed to Kalakaua Ave., which was named after King Kalakaua, the last male monarch of the Hawaiian Kingdom in 1905,” Gallego-Nakamoto explained.

This EX 8844 Series plant by Asphalt Drum Mixers (ADM) features three 150-ton silos. It’s owned and operated by Ala Imua LLC, which is part of the Road Builders Corporation family and supplies three Road Builders’ paving crews. In this image, you can see the spray platform where drivers can stop to spray release agent in the beds prior to loadout. Photo courtesy of John Ball, Top Quality Paving & Training, Manchester, New Hampshire

Managing Foot Traffic

Getting a smooth transition despite all the stops is something to take note of. Both Park and Gallego-Nakamoto spoke of the challenges the general public posed on this job.

As stated above, milling started in May and paving ended early July, according to Gallego-Nakamoto, with a total of about 6,300 tons of asphalt placed in two 2-inch lifts while the team kept tourists, surfers and shoppers from walking between machines. The scope of work included new concrete curbs and gutters; adjustment of utility manholes; and restoration of pavement striping, marking and markers, which were subcontracted.

The daily closure for milling and paving was two lanes, but when the crew cut from the gutter side to the center of the road, the last pass of the milling impacted the third lane, which was the live lane. They took extra precautions to safeguard workers and the traveling public.

Due to heavy traffic along the work area, the city denied Road Builders’ request to close three lanes and only allowed the closure of two lanes at a time, leaving vehicular and foot traffic moving around their work zone in what could have been a safety nightmare if not for careful planning and diligent execution. Gallego-Nakamoto explained the traffic control plan (TCP) in detail, saying it was a challenge to get it approved prior to the start of the project due to the limitations of lane closures:

“Because it’s a busy road, we could only close two lanes at a time. However, three-lane closure would be ideal, that way we could work on two lanes each day and have one lane as a buffer of safety precautions for both public and crew members. As a result, we made adjustments to work safely for both public and crew members. Our daily closure for cold planing and paving was two lanes; and when we cut from the gutter side to the center of the road, the last pass of the cold planing always impacted the third lane, which was the live lane. As a result, we made our last pass 3 to 5 feet so we had less impact on traffic. Time was sensitive to the project, we had 270 calendar days to complete the project. With the delays we had from getting traffic control plan approved and rainout days, we were able to get a time extension.” An additional 204 calendar days were added to the contract, with a total of 474 calendar days to complete the work.

The rolling train included an 8-ton SW654ND Sakai roller in the breakdown position.

Gallego-Nakamoto gave credit to Derek Samson, the foreman, for clever planning. “He played an important role because he mapped it all out for us.”

The general public doesn’t necessarily understand the dangers an active work zone presents or the importance of staying off an uncompacted mat. To that end, the team had to communicate with shops and hotels along the route and stay one step ahead of the work zone closure as the crews progressed. Just because the paver had passed an area didn’t mean pedestrians could safely walk past an orange cone or drivers could pull a vehicle out of a hotel’s driveway. They still had to wait for the roller operator to compact the fresh mat and meet compaction requirements. Signage and communication were key, and crew members had to keep their heads on a swivel.

The blending control screen shows the operator his five cold feed bin and two RAP bin levels with a popup screen in the corner showing production targets. Key elements are shown as illustrations with PG grade, capacities, temperatures and other metrics specified on one screen. The corresponding bins outside are prepped for production, complete with berms to prevent aggregate sizes from bleeding into the wrong bin. Both photos courtesy of Ball

The blending control screen shows the operator his five cold feed bin and two RAP bin levels with a popup screen in the corner showing production targets. Key elements are shown as illustrations with PG grade, capacities, temperatures and other metrics specified on one screen. The corresponding bins outside are prepped for production, complete with berms to prevent aggregate sizes from bleeding into the wrong bin. Both photos courtesy of Ball

Jade Richardson, the president of Road Builders, spoke of the safety team’s efforts on site. “This project was challenging due to its high visibility and popularity as a tourist destination. When I say all eyes were on us, I mean literally. Our safety manager, Lewis Boucher, sometimes doubled as traffic control to keep the pedestrians from crossing through our cut and in between the equipment just to avoid walking around the project.”

As Park stated, a typical paving job requires everyone to be vigilant, but this project required everyone’s senses to be on high alert. “While you’re working, you’re also watching everything around you,” he said, estimating thousands of tourists walked past their work zone. “Jennifer was in constant communication with all the vendors and businesses in Waikiki. She knows the tonnage and how far it’s going to pave. All our engineers do a great job, but she was on top of it.”

The paving train included the Roadtec RP-195, now from Astec Industries. This tracked, 10-foot paver was equipped with an extendible screed to accommodate the changing widths the crew handled from day to day, extending up to 21 feet wide.

As the paving crews moved down the avenue, the work zone delineation moved as well. Gallego-Nakamoto explained: “We placed precaution tape along our work areas every day. Our safety officer, special duty officers and traffic control technicians played an important role in keeping the work area safe. We tried our best to keep pedestrians crossing the road away from the work area.

“Coordination with hotel personnel was also a challenge. We needed to stay ahead of the paving work to ensure hotels were informed when we would close their driveways.”

Keeping the bike lane “safe” was another piece of the puzzle. “The bike lanes were also a challenge,” Gallego-Nakamoto said. “We needed to pave bottom and top lifts each day when paving the bike lanes to avoid any tripping hazard when opening the work area.”

Note in this image the material charging the hopper was sliding as a homogeneous mass, leaving a clean truck bed behind.

Smooth Crew Makes A Smoother Finish

Along with the personnel mentioned above, Gallego-Nakamoto pointed to the importance of Pana Widemann’s contributions to a successful project. Widemann has been in the paving industry for 15 years. She listed Widemann as an asset to the project, saying, “He was always working with the pedestrians, hotels and businesses ensuring projects would flow. He works well with the public and ensures the safety of everyone is met. He works with the foreman and project manager as far as daily production schedule.”

Richardson spoke of the effort her team put into making the project run smoothly. “Jennifer is an outstanding project manager,” Richardson said. “She wants to avoid attracting attention to herself, although I can say that this project went well because she was at the helm. Tiny but mighty, her attention to detail and her ability to communicate effectively with the crew and the city inspector are contributing factors to the success of this project. She earned and was given the respect of others who towered over her 4-foot, 11-inch frame.”

The quality control team took readings with a nuclear density gauge, showing an average 91% compaction behind the breakdown roller, and achieved a gorgeous mat over the project.

Gallego-Nakamoto has been in the industry 20 years, the past three have been with Road Builders. For this specific project, she was in charge of running the project, ensuring the scope of work was met, and working directly with subcontractors and the city agency. As Park noted above, she was on top of the details, keeping meticulous paperwork. She explained part of her responsibilities were “making sure specs were met and proper submittals were submitted before, during and after project. Communicating with Waikiki personnel was important so that businesses were aware of our closure each day.” She sent the weekly schedule to notify all businesses and worked with the foreman and engineer to ensure the project was flowing.

The collaborative atmosphere shone through the discussions with the Road Builders team. From communication to best practices, the crew kept everyone’s safety top of mind for a lengthy and high-profile mission.

The quality control team took readings with a nuclear density gauge, showing an average 91% compaction behind the breakdown roller, and achieved a gorgeous mat over the project.

“I am equally proud of this crew and their exceptional ability to work as a team,” Richardson said. “With Derek as their foreman and Pana as their QC/project engineer, they effectively communicated the daily production rates; everyone knew their task and performed it well. It was beautiful.”

The team at Central Specialties Inc., headquartered in Alexandria, Minnesota, isn’t new to achieving quality with its work. With the motto of “It’s on Us,” the full-service general road contractor has received accolades from various departments of transportation and recently expanded operations to handle the additional work that comes with success.

As demonstrated in the Highway 85 project we discussed in the October issue, they’re open to trying out new technology and they put innovation into their day-to-day business for continuing success. Let’s look specifically at an award-winning project CSI performed on Interstate 94 (I-94) in Stark County in 2023 for another example of their innovation and quality workmanship, and how it all contributes to the expansion.

SDX Trial Success

I-94 Project

The mill-and-overlay project called for two 1.5-inch lifts along 9.6 miles of two-lane interstate. Operations Manager Joey Johnson shared that it involved concrete removal and repair, as well as hot-mix asphalt (HMA) repairs before the team mobilized their HMA plant for mainline paving to the tune of 38,000 total tons—about 18,500 per lift.

The plant they used for the project is a parallel flow drum plant from CWMF, Waite Park, Minnesota, which can produce up to 700 tons per hour (TPH). CSI positioned their plant about 14 miles from the project and produced the RAP Superpave FAA 45 with a PG58H-34 asphalt cement at 295°F.

Here we can see the SDX screed pattern on the mat and the roller operators performing their passes. All photos provided by CSI

CWMF Vice President Travis Mick spoke in glowing terms of the team. “Partnering with Central Specialties has been a rewarding experience due to their dedication to excellence and integrity, which perfectly complements our own values at CWMF. Their ‘get it done attitude’ and commitment to building the best road infrastructure ensure our equipment is utilized to its fullest potential, resulting in outstanding outcomes for their projects.”

While the crew used state of the art equipment and new technology like infrared thermal mapping and the patterned SDX screed, Johnson also credits the people who take the time for best practices for a stunning finish. You see, the I-94 project won a North Dakota Pavement Quality Award for ride and density. Johnson reported the bonus-worthy overall total international ride index (IRI) was 25.8 and the average density was 98.7%.

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Those are numbers worth emulating. Here’s how they did it.

On I-94, the team was getting good density right off the bat. Immediately behind the breakdown roller, which was a CAT CB 15 with VersaVibe, purchased in 2020, they were getting a density of 92.5. In the intermediate position, on the bottom lift, they ran a CAT CW34 pneumatic purchased in 2017. In the intermediate position, on the top lift, they ran a CAT CB 15 purchased in 2018. The finish roller was a CAT CB 34.

Laying the first lift was straightforward. It was a standard mill-and-fill. On the second lift, they used the notched wedge joint system from Willow Designs LLC on the center seam to increase longitudinal joint density.

Now that the company has expanded operations to Western North Dakota, they’ve hired additional mechanics to maintain equipment rather than hauling heavy machinery to and from headquarters about 450 miles away.

First of all, they were getting good density numbers behind the screed. Johnson shared: “The Trimble infrared thermal imaging camera was used for tracking mat temperature. Combined with VETA data and analysis software it gave us good confidence with our rolling pattern coverage which resulted in good densities.” As mentioned above, they were seeing densities of 92.5 behind the breakdown roller.

“To be honest, this [thermal mapping] is a very helpful tool to be able to better help get density and ride, seeing issues and ways to improve rolling patterns,” Johnson shared.

The crew wasn’t using a material transfer vehicle on this project—just best practices and a cohesive team. The paver operator, Tomas Chavez, has been with the company for two years and was at the helm of a CAT AP 1055F paver equipped with the new SDX screed CSI is testing for Caterpillar.

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Johnson shared that the paving widths varied along the project from 10 to 12 to 16 feet, yet the crew handled the changes smoothly. The dump man on the project was Jose Becerra, and the screed operator, Carlos Pasillas, has nine years of experience.

“Carlos is a very strong leader for our main line crew and a positive person,” Johnson shared. “I believe the reason we won the award was that the crew works together to make the best road possible. There is really a team atmosphere when it comes to Plant 4 crew for CSI. It really starts with John Fales leading the crew and developing them and then the crew taking ownership of the paving. At the end of every job the crew is always asking how they did on ride and density, which shows they have pride in their work.”

Jill O’Brien operates the intermediate roller toward the award-winning density and ride numbers on I-94.

Winning Against Challenges

CSI began the I-94 project April 4, 2023, and finished it Aug. 14. During those four months, the crew had challenges to overcome to hit an award-winning completion.

“There was a lot of concrete removal, and the state would only close down a certain amount of interstate at a time,” Johnson explained. “Then we would have to go out and patch back in to let traffic back on it. It was difficult scheduling to keep subs on track working and getting a crew deployed on a short window to get the patching done.”

He gave credit to Dave Winkler, the project manager, and John Fales, the paving superintendent for their leadership and expertise on the job. “The project manager really kept a close eye on the subs on when they would be completed with their phases and lining up our paving crew to come in and patch in mix, then move the subs to the next phase to complete to stay on track for the job.”

Supervisor John Fales and Dump Man Jose Becerra—in the foreground—work on the I-94 project.

One aspect of the project that the crew gave extra attention to was the centerline joint. “Making sure centerline is clean after the milling machine,” he shared. “On the bottom lift we had some longitudinal joint failures that we had to mill out and repair because we did not get centerline completely clean but after finding the issue the crew took ownership and got the project back on track.”

At the end of the day, the crew handled best practices and challenges with professionalism that Johnson’s proud of. “I like the fact that when there were issues the crew stuck together to get the job done. They never pointed the finger; they owned the issue and moved on. That is what makes a great crew.”

The completed side of I-94 looks gorgeous and won a 2023 Hot Mix Asphalt Quality Award.

New Location

If you think the logistics of the I-94 project look complex on paper, consider what it was like in the field. With the amount of work available across North Dakota, CSI management decided it was time to expand operations. They purchased a building to start a shop and office in Watford City, North Dakota.

“We expanded with offices and a shop in Watford City, North Dakota, in January of 2024,” Johnson said. The team then used the office space to hold interviews every two to three weeks and set up the offices and a conference room for the project managers to use during the 2024 construction season for both a home base and for meetings with local agencies when needed.

Joey Johnson is the operations manager for Central Specialties.

Immediately behind the breakdown roller, they were getting a density of 92.5.

“The shop is running well,” Johnson shared. “We have three current mechanics working out there and are looking to staff up to four to six full-time mechanics in the future. That will really save us time and money in the future not hauling our equipment in the area all the way back to our main shop in Alexandria, Minnesota.”

Fleet maintenance, whether in Watford City or Alexandria, is another key to CSI’s success. “We really feel that we keep our equipment up to date and have some of the best technology. We swap out our mainline pavers every three years and we send our crews to paving classes every year to keep them up to date on new methods and ideas. We are constantly trying innovation to see what works, such as the new SDX screed CAT has us trying out.”

With updated technology and innovation for a fully trained workforce, CSI takes ownership of its success on every project. The award-winning I-94 project exemplifies this attitude and aptitude and offers a great example of the company’s motto “It’s On Us.”

Testing screed types side-by-side in the badlands of North Dakota proves industry can increase density, improve ride with patterned screed, innovation, best practices.

By paving in echelon up and down the hills of Highway 85 in the North Unit of Theodore Roosevelt National Park (TRNP), the award-winning team of Central Specialties Inc., headquartered in Alexandria, Minnesota, tested densities and smoothness achieved behind the SDX screed plate design from Caterpillar alongside the traditional SE60 screed plate design. The crew performed this 10.214-lane-mile build in spring of 2024, achieving an average density improvement on the SDX lanes of 1.7% directly behind the screed and 1.2% after the finish rollers. The overall smoothness results paint a sustainable picture for the asphalt industry.

Two Weiler windrow elevator pickup machines and two Cat AP1055F pavers with SE60 V-XW screeds worked in echelon to place two lifts. One screed was equipped with a traditional screed plate while the other was equipped with the SDX patterned screed plate.

“We increased the density by 1 to 1.5% and ride by 10% behind the paver equipped with the SDX screed compared to the traditional one,” Bryce Wuori said. He’s the proprietor of Pavewise, headquartered in Bismarck, North Dakota, and was hired by Caterpillar to serve as a consultant on the project. “We saw a 25% decrease in standard deviation. The 10,000-foot view on this project was innovation and technologies that are pushing the industry forward can be proved with this data.”

The Theodore Roosevelt National Park is divided into three parts in western North Dakota, which include a South Unit and Elkhorn Ranch Unit. CSI paved in the North Unit in the spring of 2024.

The crew built longitudinal joints during echelon paving with the notch wedge joint system from Willow Designs LLC, East Berlin, Pennsylvania.

Innovation Everywhere

Not only was the team using the innovative SDX screed plates on one of the pavers, but they also employed thermal mapping, intelligent compaction (IC) and multiple data-collection technologies to assess quality control/quality assurance (QC/QA) along the way.

One of the newer tools on hand was the GroundTruth system from Pavewise, which helped monitor environmental conditions in real time. This solar-powered, mini weather station was situated at the project site to communicate with the Pavewise software when inclement weather was rolling in. It also documented conditions for the team. For example, during southbound paving on May 29, the average ambient temperature was 64°F with an average wind speed of 9 miles per hour (MPH). That night, the area experienced 1.2 inches of rain. During northbound paving on May 30, the average ambient temperature was 57°F with an average wind speed of 11 MPH.

The crew set up Pavewise’s GroundTruth system, which helped monitor environmental conditions in real time. Here you see the solar-powered mini weather station, which communicated with the Pavewise software to alert the crew when inclement weather was rolling in and documented weather conditions.

The CSI team executed paving both lifts of more than 12,000 total tons along the 10+ lane miles in two days.

The TRNP project in McKenzie County required paving 10+ total miles from the park entrance to County Road 30 (23rd Street NW). The crew was responsible for grading, aggregate base, hot-mix asphalt (HMA), culverts, box culvert, a pedestrian walking trail, the retaining wall, signage, pavement markings and incidentals. The mix design used on the project was North Dakota’s FAA45, which uses a PG64-34H binder. The CSI team produced the mix at its parallel-flow drum plant from CWMF, Waite Park, Minnesota, which was located outside Watford City. Typical production was 610 tons per hour with a propane-fueled Hauck Eco Star 200 burner. The average mix temperature out of the trucks was 306°F.

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Belly-dump, live-bottom and tandem trailers delivered material ahead of two Weiler windrow elevator pickup machines, which in turn fed the two Cat AP1055F pavers with SE60 V-XW screeds vibrating at 1,200-1,400 VPM, and working in echelon.

“The paving widths were 18 feet behind the traditional screed AP1055 and 20 feet with 4-foot slough behind the 1055 with the SDX screed,” Wuori shared. See Figure 1 for more detail.

The base course was 2 inches compacted; the wearing course 1.5 inches compacted. Longitudinal joints were created with the notch wedge joint system from Willow Designs LLC, East Berlin, Pennsylvania. Jerod Willow, proprietor of Willow Designs, spoke to the efficacy of using a joint-making system with a vibrating screed.

“Screed vibration has no effect on the notch wedge device or produces no damage to the joint itself,” he said. “Willow Designs actually has options for electric vibrators on the notch wedge devices themselves because I believe using screed vibration is a good thing to a certain extent.”

Thanks to the GroundTruth system from Pavewise, the team collected environmental conditions data during the project. On May 29, while paving southbound, the average ambient temperature was 64°F with an average wind speed of 9 miles per hour (MPH). That night, the area experienced 1.2 inches of rain. The seasoned professionals at CSI have excellent stockpile management practices and know how to handle a heavy rain event. Paving northbound on May 30 saw an average ambient temperature of 57°F with an average wind speed of 11 MPH and consistently good data points in the northbound lanes.

Willow expanded on his theory and offered a tip for vibe settings. “Having screed vibration set at a moderate and manageable speed is key to help manipulate, turn and lock the aggregate in the asphalt mix together as it is protruded under the screed. A way to find manageable screed vibration per minute (VPM): stand a shovel on the catwalk of the paver screed. If it vibrates off and falls down, the VPM is too high.

“I believe too high screed VPM just causes excessive wear and tear on equipment with minimal results in increased mat density,” Willow continued. “Think about it like this: we are trying to keep the screed of the paver planted to the ground to assure a good ride quality of the pavement we are placing, but now using vibration at a high VPM is like having the screed of the paver do all these ‘micro jumps.’ Think about how vibration impacts work on roller drums. High VPM on the screed seems counterintuitive. From a highly technical standpoint, paver screeds should oscillate to be effective and produce minimal deviations of mat quality as far as smoothness and rideability.”

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To assess mat temperature behind the screeds, the crew employed paver-mounted thermal profiling (PMTP). The SDX-equipped paver employed the Caterpillar thermal camera system, and it collected data showing the average lot temperature behind that screed was 267°F. It also showed a low to moderate incidence of thermal segregation. The traditional paver employed the MOBA thermal camera system, and it collected data showing the average lot temperature behind the traditional screed was 259°F. It also showed a moderate to high incidence of thermal segregation. Wuori indicated: “Thermal consistency behind the SDX produced a lower thermal segregation index than the traditional screed.”

He explained: “The 3D textured surface of the SDX screed kneads the aggregate together, forcing it to move into position. This action develops more density and thermal consistency behind the screed with this manipulation.”

Here you can see the pattern on the underneath of the SDX screed plate. The straight edge shows the “wave” or side view of the patterned plate.

Here you can see the pattern on the underneath of the SDX screed plate. The straight edge shows the “wave” or side view of the patterned plate.

Multiple steel drum Cat rollers equipped with intelligent compaction (IC) and Versa-Vibe worked in breakdown, intermediate and finish positions to achieve compaction. The IC used included a CB-460 display with Trimble Systems, VRS positioning data and WorksOS. Each of these provided the operator with a means to track passes, temperatures and impacts-per-foot to ensure the highest quality of rolling was being achieved on the project.

For the SDX-equipped paver, the rollers were a Cat CB15 in breakdown position and another Cat CB15 in the intermediate position. For the traditional-screed paver, the rollers were a Cat CB66 in breakdown position and another Cat CB66 in the intermediate position. Both paving lanes shared a Cat CB15 in static mode in the finish position.

Paving team Bradley and Jill O’Brien are a married couple who handled compaction behind the SDX screed plate. Jill operates the breakdown roller while Brad operates the intermediate and finish.

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They shared that the mat behind the SDX, “takes fewer passes to get density compared to the conventional screed; less water consumption. When following a rubber-tire roller, the turn around spots are smoother and all-around marks less visible. The SDX screed also prevents less mat tear marks from the steel rollers.”

Using IC was a benefit for the O’Briens as well. They explained the system allowed them to see how many passes they’d completed and where they’d already rolled. “Just like flying an airplane at night—you know where the runway is.”

The team gathered thousands of data points during and after paving to prove the award-winning team of Central Specialties Inc. executed a stellar roadway project for the Theodore Roosevelt National Park with both traditional and patterned screed plates. The data also showed overall smoothness results that paint a sustainable picture for the asphalt industry, proving the innovative use of the SDX patterned screed offers a quality option for contractors.

Smooth Results

With compactors working on the rolling pattern, the team could start gathering density data. They used a NoNuke density gauge from Instrotek Inc., Research Triangle Park, North Carolina, to collect 360 points—97 of those behind the screed—before rolling. They used the PaveScan 2.0 RDM from Geophysical Survey Systems Inc., Nashua, New Hampshire, to gather 19,609 DPS data points—9,932 of those behind the SDX screed. An operator from Robison Grinding & Profiling LLC, Gillette, Wyoming, drove the SSI Zero-Speed Inertial Profiler along the project’s base and surface/wear courses.

The results showed a high-quality job. Starting with the non-nuclear density gauge results, Wuori reported the average density directly behind the SDX screed was 91.5%; the average behind the traditional screed was 89.8%. Notice that’s not a bad number. The CSI paving crew was handling mix delivery and paving with best practices. But they were seeing a 1.7% density increase immediately behind the screed with the patterned plate.

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John Fales, CSI paving superintendent on the project, said, “This paving crew is like a well-oiled machine. They take pride in the work they do every day and pave some of the best asphalt roads in the Midwest.”

The non-nuclear density gauge numbers behind the finish roller told a similar story. The CSI paving and rolling train was knocking it out of the park, achieving 93.6% average density in the traditional-screed-plate lane. They hit an average density of 94.8% in the SDX lane, which is a density increase of 1.2%.

Moving to the DPS data on the SDX section, both northbound and southbound driving lanes offered a dielectric value of 4.50 with a standard deviation of only 0.11. This converts to a density of 94-94.5%.

This is the gorgeous mat behind the screed equipped with the SDX patterned screed plate.

This is the gorgeous mat behind the screed equipped with the traditional screed plate.

Here you see the two mats side by side with the hot joint created down the center.

“To CSI’s credit, this was the lowest STD ever collected with the PaveScan DPS unit on an asphalt surface,” Wuori shared. “A decrease in standard deviation equals more consistent average densities. A lower standard deviation is better for percent-within-limit (PWL) projects and decreases the chances of lower/higher cores or dropping the average of a lot down to less of a pay factor.”

The DPS data on the traditional section, both northbound and southbound passing lanes, offered a dielectric value of 4.40 with a standard deviation of 0.15. This converts to a density of 93.5-94%.

The zero-speed inertial profile data is in Table 1 below. Wuori summarized the results, showing the driving lane average difference—with the SDX—was 25.77 with a decrease in roughness of 2.61. The passing lane average difference—with the traditional screed—was 23.26. “This shows us a 10% improvement with the SDX,” he shared.

Patterned Screed Plate, Smooth Mat

Despite its destructive nature, the team had to take some cores—11 random cores behind the SDX screed, 11 random cores behind the traditional screed and 10 randomly along the joint. The engineers Kadramas Lee & Jackson shared that none of the cores behind the SDX screed failed and only one of the cores behind the traditional screed failed to get above the required 92%. This testing showed a 0.44% density increase behind the SDX screed.

The CSI crew used paver-mounted thermal profiling (PMTP) to assess mat temperatures immediately behind the screeds. The SDX-equipped paver employed the Caterpillar thermal camera system, and it collected data showing the average lot temperature behind that screed was 267°F. It also showed a low to moderate incidence of thermal segregation. Consultant Bryce Wuori shared: “Thermal consistency behind the SDX produced a lower thermal segregation index than the traditional screed.”

What the pilot project on Hwy. 85 showed is the use of innovation and best practices brought a slew of data to the industry. This data proves the innovative use of the patterned screed plate, PMTP and IC can offer improved densities and a smoother ride for the taxpayer. When asphalt pavements have a solid and sound foundation, they last longer and offer not only a quality driving experience for the end user, but also a more sustainable option for agencies/owners. The use of such innovative technologies is a win all the way around.

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.

Sunland Asphalt performs mill and fill on Miami Formula 1 track with echelon paving ahead of successful Grand Prix

In the Formula 1 world, millimeters matter in both racing and paving. Management at Sunland Asphalt & Construction, Littleton, Colorado, knew they would need their A team on hand to handle the 2023 resurfacing project at the Miami International Autodrome, home of the Formula 1 Miami Grand Prix. They mobilized 75 internal employees, 15 technical specialists and 40 pieces of heavy equipment from around the country on 35 separate transport loads.

The project’s scope consisted of milling 2 inches of the existing track and repaving it with a highly specialized asphalt mix designed to Formula 1 standards. Crews were to repave the track at 2 inches thick for a total of 9,500 tons over an eight-day period.

Construction scheduling for the 3.36-mile anticlockwise circuit, which winds around the Hard Rock Stadium in Miami Gardens, had to be choreographed around the stadium’s other events, including the end of the National Football League season, a jazz music festival and the Miami Open tennis tournament. The International Automobile Federation also required Sunland to have the mix put down 60 days before its big event for the material to properly cure.

Needless to say, it took a lot of coordination for Sunland to make this happen and the Wirtgen Group was just one of the many partners in place to help.

Sunland crews used three pavers working in echelon to prevent cold joints along the 50-foot-wide track, paving at a very efficient pace of only 6 fpm.

Step 1. Mill. The crew from Sunland Asphalt & Construction, Littleton, Colorado, used three milling machines to precisely remove 2 inches from the existing track.

The Need for Speed—and Grip

In 2022, Miami held its first Grand Prix event on the track. When drivers expressed concerns with the grip on the pavement, track owners decided to lay fresh asphalt ahead of the 2023 race. The track management hired Tilke Engineers & Architects, headquartered in Aachen, Germany, to oversee track resurfacing, which they said would ultimately improve the “spectacle” of the 2023 race.

Sunland was hired to complete the mill-and-resurface of the track and began work to remove the existing surface in the early spring of 2023.

Sunland Asphalt trucked all their equipment in to ensure crews were familiar and comfortable with their equipment and processes. They used three pavers working in echelon to prevent cold joints along the 50-foot-wide track. The pavers were also moving at a very efficient pace of only 6 fpm to ensure paving smoothness.

The mix design for the track included 60% US-mined granite from Georgia with the remainder of the aggregates being locally sourced lime rock from Southern Florida. These aggregates ensured the grip needed on the course.

Step 2. Fill. Three pavers worked in echelon at a steady pace of 6 feet per minute to ensure no cold joints interrupted a smooth mat. Here you can see a Weiler material transfer vehicle feeding the hopper insert of one of two Vogele Super 2000-3i pavers to assist in smooth, constant material control.

Technology Meets Tight Tolerances

In addition to the three Wirtgen mills, Sunland used three HAMM HD+ 80i rollers and two VOGELE Super 2000-3i asphalt pavers. The Wirtgen Group technology on these machines is “plug and play,” which allowed the team at Sunland to get up and running with these machines easily.

“The plug and play feature on all these machines has been a huge advantage to us as a Topcon provider, making the installs quick and easy,” Tony Carden, intelligent paving product manager at RDO Equipment said. “We’re also able to provide serviceability for them both on the dealer side and from the manufacturer side. It’s a win-win.”

The project’s scope consisted of milling 2 inches of the existing track, then repaving 2 inches thick with a highly specialized asphalt mix designed to Formula 1 standards, for a total of 9,500 tons over an eight-day period.

Thermal Imaging

The pavers on the job were equipped with a temperature monitoring system. Thermal cameras were mounted to the pavers and used to find any temperature differences that could indicate potential segregation in the mat as it was being laid.

“The thermal profiling that we’re using on the pavers gives a rundown of where the pavers were, where they’re going, at what speed they are running and at what temperature,” Greg Hughes, project engineer at Sunland said. “If one isn’t getting to a high enough temperature, we can go back and look at it and see what happened and fix it and that’s a great tool for us.”

To address racecar drivers’ concerns about pavement grip, the Miami International Autodrome’s Formula 1 Miami Grand Prix track was milled and resurfaced ahead of the 2023 big event. All photos courtesy of C2C Visuals

Intelligent Compaction

“The intelligent compaction on all the rollers shows us our roller patterns throughout the day,” Hughes said. “It provides us real-time documentation of the areas we are hitting and if we’re hitting any areas more than we should. We’re also able to know if we should be vibrating more or less as well.”

With the HAMM Intelligent Compaction system, users can set a designated number of passes ahead of paving. The system shows the operator, on the in-cab display, how many passes have been completed.

Sunland management says they also use the intelligent compaction system as a training tool. “We sit with our roller operators, and we can show them where we might be able to improve on future jobs.”—Greg Hughes

Step 3. Compact. The compaction team set a rolling pattern behind the pavers to achieve optimum densities and a smooth driving surface incorporating three HAMM HD+ 80i rollers.

Sunland management says they also use the intelligent compaction system as a training tool.

“We use it in the office to see where we could be more effective,” Hughes said. “We sit with our roller operators, and we can show them where we might be able to improve on future jobs.”

The crews finished paving the 19 turns of the course on the Autodrome’s schedule, and the 2023 Miami Grand Prix was a success thanks to the hard work and dedication of the people behind the machines.

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.