Preferred Materials Executes the Plan to Get the Best IRI in Florida
BY Sandy Lender
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 GW850 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.
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.
“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.”
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.”
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.”