Paving contractor Glenn O Hawbaker Inc. of State College, PA, selects paving equipment based on simple criteria — it chooses companies that earn its business based on just-in-time service, parts delivery, and the equipment’s reliability.
Hawbaker is a third-generaiion-family company, established in 1952, and one of the largest HMA production and applications companies in Pennsylvania.
According to Patrick Hawbaker, paving superintendent, the company has nine paving crews and nine complete sets of paving equipment. For producing the hot mix asphalt (HMA) the company owns five quarries, each with crushing/screening plants and seven HMA production plants. Besides supplying aggregates to the HMA plants rock is crushed for producing roadbed material.
All of these resources are being used this year to lay down 2 million tons of paving. About half of that paving will be Superpave. Of the total paving laid this year, 1.2 million tons are for state and local government projects. The rest of the paving is for privately-owned projects such as parking lots and roadways at commercial/industrial facilities.
Hawbaker considers its Roadtec and Hypac equipment to be the flagships in the fleet. The reason being, it is this equipment that is performing significantly in paving productivity and the quality of the mat.
Troy Franks, major-projects coordinator of Hawbaker, said its Roadtec/Hypac compaction system is producing consistently high-quality paving results with exceptional road smoothness. “We are focused on doing high-quality paving for receiving the PennDOT bonuses it awards,” said Franks. “The better the ’ride’ the bigger the bonus. For this Penn DOT work, I find the Shuttle Buggy, material transfer vehicle (MTV) by Roadtec is the best. I am achieving higher production and higher quality paving with this system as opposed to the more conventional paving systems we have. On an average, we get 100 tons (90 t) per hour more of HMA laid by using the Shuttle Buggy in our paving system.”
Four major conditions, according to Franks, influence the smoothness results of its paving projects. One is the uniform quality of the mix as it is being laid by the paver. Secondly, is the paver’s continuous paving activity, made possible by loading it with a MTV (material transfer vehicle such as the Shuttle Buggy). Using a MTV eliminates the chance of a dump truck accidentally bumping the paver when loading the HMA. Thirdly, is the uniformity of the mat’s temperature when being laid and the absence of pattern segregation in the mat. Finally, is the compacting of the mat. Some of the new vibratory compactors on the market are quite sophisticated, eliminating many of the variables in compacting that are associated with older models.
In the past, aggregate segregation and temperature deviation within the HMA have been two major concerns for Hawbaker. “My concern was based on the traditional methods we were using for handling and laying the asphalt mix,” said Franks. “We were using conventionally-designed pavers with no MTVs and our compactors were not on par compared to the new Hypac rollers.
“Dumping the mix directly from a truck into a paver would cause some of the larger size aggregates to segregate from the finer aggregates,” continued Franks. “Another problem was, the mix did not always have a uniform temperature by the time the delivery truck reached the paving site. Of course there is little the paver can do to rectify this problem. Only re-mixing of the asphalt mix at the paving site can reunify its temperature.”
According to Franks, both of these problems have been eliminated by including the MTV in the paving system. The company bought two Roadtec SB 2500B Shuttle Buggy MTVs and a Roadtec SP-l00 Stealth paver.
The first significant project using the two MTVs and two Stealth pavers was a paving project at the University Park Airport in State College. A total of 10,400 tons (9,360 t) of HMA was laid and compacted in 23 hours on this project. The window for completing the project was because the airport needed the runway reopened as soon as possible. Besides serving Sate College and its surrounding area, it is a main transportation system utilized by the 45,000-student population of Penn State University.
According to Franks, if he would have used the more conventional dump truck-to-paver asphalt-mix transfer method, it would have necessitated three pavers to accomplish what was accomplished with two. “It is simple why our production increased. The pavers paved continuously, so no lost paving-time associated with conventional paving methods was experienced,” said Franks.
The Hypac vibratory rollers were added to the MTV/Stealth paving system in time for a new Penn DOT interstate highway resurfacing project. On this project half of the 44,000 tons (39,600 t) of Superpave was laid with outstanding results.
According to Franks, the most notable results of the paving job were the uniform temperature of the asphalt mix when laid, the substantial reduction of aggregate segregation and the smoothness of the mat. He credits the material transfer equipment and the vibratory rollers for this paving success.
These smaller projects led up to the company’s major Superpave project on a section of SR 15 that was under construction in Tioga County, PA, about 30 mi. (48.3 km) north of Williamsport.
Hawbaker was responsible for paving a four-lane section of road, 6.1-mi. (9.8 km) long. Paving started in June 2000 and was completed by September. A total of 906,000 tons (185,400 t) of Superpave was laid. The base course was 141,000 tons (126,900 t) of a 1.48-in. (3.75 cm) base-course. This was followed by applying 35,000 tons (31,500 t) of a .75-in. (1.9 cm) binder and finished with 30,000 tons (27,000 t) of a .5-in. (1.25 cm) wearing course.
Both sandstone and limestone were used as the aggregates for this project’s asphalt mixes. The company’s HMA plant produced 550 to 600 tons (495 to 540 t) per hour.
The best production day for laying asphalt was 4,433 tons (3,990 t) in 12 hours. For the project, the production ranged from 3,500 to 4,000 tons (3,150 to 3,600 t) per 12-hour day. This production was achieved using one Shuttle Buggy, one SP 100 Stealth paver, one C766C, two C778B Hypac compactors and a Caterpillar PS 200 rubber-tire static roller. The asphalt mix was hauled to the paving site in 35 Mack tri-axle trucks with 25-ton (22.5 t) capacity aluminum dump bodies featuring round bottoms.
Bonus payments received from the DOT because of exceptional high-quality paving is a benefit that helps contractors increase their profits. Many DOT agencies award bonuses that are dependent on the smoothness of the roadway. For the SR 15 project, there was $71,000 in bonuses. Hawbaker received all $71,000.
Franks attributes the high-quality paving achieved on this project to a number of factors. Firstly, the round-bottom dump truck’s efficiency in dumping asphalt mix. The free-sliding of the material from the dump body into the Shuttle Buggy helps to reduce aggregate separation.
Secondly, the material transfer vehicle played an important role. It re-blends the HMA, thus giving the mix a uniform temperature as it loads the paver. Temperature segregation caused by the cool-down of the mix when transported to the paving site. Especially on cooler days, the mix closest to the dump-body sides, top and bottom cool down more rapidly than the center of the mix.
Using a Shuttle Buggy, the problem is eliminated because it features two triple-pitch remixing augers for reblending the asphalt mix, thus obtaining an even temperature throughout as it is conveyed to the paver. The uniform density in the mat and a minimal temperature variation affords compacting of the mat with minimal deficiencies and the result is smoother pavement.
According to Franks, this equipment combination is working so well that the company has purchased a third Shuttle Buggy and is about to purchase another Stealth paver. “We are getting consistent-quality paving results, high production and, where applicable, we are getting bonuses from the DOT. You bet we will buy more of the same equipment as we need it,” said Franks.
