In a natural paradise, things seem perfect. And, they should remain as close to perfect as possible. Where environmental concerns are high, so are construction standards. But when aggregate and other resources are extremely scarce, contractors are doubly challenged to get their job done correctly and quickly.
This was the exact challenge accepted by a major Hawaiian contractor, Grace Pacific Corp. Being surrounded by perfection, they demand the same of themselves. “Or as close to it as we can get,” stated Darrell Goo, senior vice president of construction at Grace Pacific’s home base in Honolulu. “We are committed to continually upgrading our asphalt plants and paving equipment to meet or exceed environmental requirements by taking advantage of the technological advances available to us.”
Road for the stars
A road needed to be constructed at the base of Mauna Kea Mountain on the Big Island of Hawaii. This was not just any site. The elevation and location of Mauna Kea make it a prime location for astrological observation. The United Kingdom, Canada, Chile, Brazil, Argentina, France and Japan have some of the most powerful telescopes in the world there.
The Army and Marines also train at Pohakuloa Military Reserve that shares the mountain with Mauna Kea State Park. The improved road would not only benefit tourists, scientists and the military, it would simplify travel to the west side of the island from the east. Instead of following the coastline, Mauna Kea could now be easily surmounted. This would reduce the 110-mile drive to 75, plus cut travel time from 2½ hours to only one. The benefits of the project were obvious, but the conditions were complicated.
The road would be 16 lane-miles, utilizing 225,000 tons of 7-in. HABT. The entire asphalt course was crushed onsite and PG 64-16 asphalt was used. The HABT was to be laid in two lifts with a 2-in. Superpave top lift. But the 6,400-ft elevation caused the temperature to drop to 40°—not exactly tropical conditions. Compaction, smoothness and standard FHWA specifications had to be met regardless of these temperatures. Working quickly became a critical factor.
The optimum window to lay and work with the asphalt was narrow. The goal was to pave 250 tons per hour plus compact and finish it before it cooled. Grace Pacific needed a technological advancement that would be a solution to this problem. This proved to be a vibratory pneumatic-tire roller.
Fast times
What has Shiroma and others excited is the ability of the vibratory pneumatic-tire roller—a Sakai GW750—to vibrate its rubber tires. Like a conventional static pneumatic-tire roller, it develops a kneading action that helps to seal the surface of the mix. The vibratory action on the tires results in a very thorough compaction of the mix throughout the thickness of the mat. Testing in Japan and the U.S. has shown density to be more uniform throughout the pavement layer.
According to Sammy Nose (pronounced no-say), “Conventional static and vibratory processes would not give us this homogenous density result. In fact, this result cannot be detected by a nuclear gauge test and can only be seen by segmented core sampling that individually tests the top, center and bottom layers of the mat. This result should translate into the long-term durability of the mat surface.”
The vibratory system is designed much like a steel-wheel vibratory, but with multiamplitude, vibratory eccentric systems housed in both front and rear axle systems. These systems generate dynamic forces that help to achieve density far faster than conventional rubber-tire rollers. According to Shiroma, “The ground speed of the [vibratory pneumatic-tire roller] is higher than that of our conventional pneumatics. Today’s mix designs, plus the public demand that we get the job done faster, push the need for speed. And the size of this roller and its articulated steering makes it a great tool for smaller jobs that include tight turns.”
Grace Pacific has put its vibratory pneumatic-tire roller to good use on Hawaii’s main roads: the Kalanianaole Highway, the Kamehameha Highway, the Farrington Highway and many others.
“We like the flexibility this machine gives us. We can have it out on mainline production today, then use it on a smaller road or parking area tomorrow,” Shiroma said.
Passing grade
The tires are flatter and much wider than a conventional pneumatic-tire roller. A bigger footprint means a greater overlap, resulting in a very smooth finish.
“These are the things that lead us to [purchasing a vibratory pneumatic-tire roller],” said Shiroma, “and it has proven itself to be of great value in the field. No doubt about it. The shape and width of the tires promote the smooth finishes we need.”
The vibratory system speeded up the rolling pattern for compaction, practically eliminating the need for a finish roller. Considering how precious time was on this job, this was a substantial benefit.
Smoothness is not the only attribute of the vibratory pneumatic-tire roller. “We are getting density in less passes,” said Shiroma. Fewer passes means higher productivity and a better bottom line. And in many cases, reducing the time required to gain compaction enables contractors to reduce their bids and gain additional business. Compaction gains are achieved by the unique vibration systems, which are designed into each of the axles of the vibratory pneumatic-tire roller. Like steel-drum vibratory rollers, the machine offers a choice of centrifugal force outputs, which are controlled right from the operator’s station.
At high force, the roller Grace Pacific is using on the job is said to develop compaction forces equal to a 55,000-lb pneumatic-tire roller. This kind of force would be extremely useful on thicker base materials and even on sub-base work. With an operating weight of only 20,000 lb and a footprint of about 87 in. x 179 in., the machine is much easier to transport and saves on diesel fuel as well. Grace Pacific operators are trained to adjust the centrifugal force output to suit mix designs, mat thicknesses and ambient conditions.
According to Shiroma, “Another time-saving feature with the [vibratory pneumatic-tire roller] is that we can easily change forces on the run, right from the operator’s station, without the need to get off the machine. Our machine settings are usually determined while running test strips. But the operator has some decision-making power onsite, should mix or ambient conditions change.”
Meets the profile
Grace Pacific operates eight modern asphalt production facilities on the islands of Hawaii. Paving crews throughout the islands are equipped with the latest machinery available and are trained to operate it safely and efficiently. With the shortage of aggregate on Hawaii, the practice of profiling and recycling is growing daily plus is an environmental necessity.
One great benefit of the vibratory pneumatic-tire roller yet untested by Grace Pacific is its ability to seat overlays into previously profiled surfaces. When rolled statically, new asphalt overlays tend to bridge the profiled grooves. This is another thing you can only see by coring. Minimal interlock is achieved and overlays have a tendency to delaminate, causing additional problems and further expense.
Steel-drum vibratory rollers can improve this situation, but the vibratory pneumatic-tire roller has the unique ability to massage the overlay into the profiled base for a totally integrated, long-lasting surface.
Grace Pacific’s slogan—“When Expectations are High, Excellence Endures”—fully supports the company’s philosophy when building roads throughout this island paradise. Grace Pacific has just won two prestigious national awards from the National Asphalt Pavement Association for 2006, the Diamond Achievement Commendation for Excellence in Hot-Mix Asphalt Plant/Site Operations for Maui and the Outstanding Brochure Award. They look to original equipment manufacturers to design the products that will protect their beautiful environment while continuing to advance Hawaii’s commercial, military and travel industries. And the vibratory pneumatic-tire roller is a perfect fit for this philosophy.
