Setting the Smoothness Standard

The DOT required a material transfer vehicle to be used on the project and Glover equipped its paving crew with a Roadtec Shuttle Buggy, which proved beneficial in dealing with some of the sporadic trucking problems the paving crew experienced.

Park has tried to keep 30 trucks a day hauling to the project to accommodate both the full-depth reconstruction work and the surface overlay crews. Traffic delays often added to the 30-minute trip from Glover's portable asphalt plant to the actual workzone, so the material transfer vehicle helped to eliminate segregation and maintain a consistent temperature to the mix before it reached the paver.

Uchima used a Hypac 84-inch vibratory roller to generate 3,400 vpms traveling at two to three miles per hour for the breakdown pass and a Hypac 78-inch static roller to finish compaction, with the rolling pattern set up to achieve 94 to 96 percent density.

"We've had to pay close attention to our rolling pattern when working on the travel lane which has the crown to ensure a consistent profile to the slope," Uchima says.

Making the mix

Keeping the paving crew supplied with a consistent quality mix has been the responsibility of Rich Gribbin, quality control manager for Glover. With 30 years of experience in the asphalt business, Gribbin is well-suited for the task and the challenge of designing a mix using porous volcanic aggregate. Gribbin moved to Hawaii from New Jersey, where aggregate has a .5 to .7 absorption rate. The aggregate used in asphalt projects in Hawaii has an average 1.7 absorption rate.

Mixes designed for projects like the Queen Kaahumanu Highway resurfacing project require a richer asphalt cement content to bind the porous volcanic aggregate together when compacted.

"It's like a Superpave mix, but still considered a Marshall mix design, with the DOT specifying the aggregate gradation range and percent of liquid asphalt cement required to achieve stability, flow and air void percentage," Gribbin says. "Other than that, it really doesn't pose any paving or compacting problems. It's like any other mix design used on the mainland."

Glover purchased and set up a CMI/Terex 300-tph counterflow portable drum plant near the construction site. The plant is equipped with four cold-feed bins and two 30,000-gallon AC storage tanks. Gribbin used a PG 64-16 asphalt cement to bind the 5/8-inch, 3/8-inch and fine aggregate for the project.

"The aggregate size gave our crews the ability to achieve a more uniform compaction of the overlay, along with the DOT's required 91 to 96 percent density requirement," Gribbin says.

Gribbin is supported by two quality control technicians, one at the plant monitoring mix production and one at the project taking core samples (approximately five samples for each three-mile section the paving crew put down in a day) and density readings. The field technician also conducts a profile reading at the end of each day to make sure smoothness specifications are still on target.

Many smooth miles ahead

Keeping an eye on all the details required to achieve the DOT's smoothness requirements, Glover's milling and paving crews have been averaging an IRI rating of 20 to 30 inches per lane mile.

"We know we'll collect full incentive if we can keep the IRI smoothness spec below 60 and we've been able to do much better because everybody working on this project is really determined to make this the smoothest road they've ever worked on. We really have a great bunch of guys working on this project," Uchima says.

When paving is complete by the end of summer, Glover's crews will have put down 100,000 tons of some of the smoothest asphalt you'll travel, and the asphalt contractor expects to complete the project three to four weeks ahead of schedule, which could add another $300,000 bonus to the expected smoothness bonus. And you can be sure that once the $10-million resurfacing project is complete, the original road that was constructed in 1972 will provide many years of smooth and reliable service to motorists traveling the Kona side of The Big Island of Hawaii.