Anderson Columbia received the hot-mix paving industry's highest honor for its work on I-75 in Lowndes County, Ga., in 1996. The 10-mile project, which took place just across the Florida border, used 146,800 tons of HMA in 61.8 lane miles of construction.
Totaling $13 million, the project involved milling and overlay of the highway's existing four lanes and the addition of two 12-ft lanes inside of the existing roadway. Inside of the new lanes a 10-ft shoulder was constructed and a guardrail installed in the median. The project also entailed the removal of an overpass that spanned a now abandoned railroad right of way and the lowering of the grade of the old approaches.
Award-winning features
Rideability and appearance stand out as the two most striking features of the project. Randall Marchant, technical services engineer for the Georgia DOT, said, "The Georgia Department of Transportation has an audit program where we go out and measure the smoothness of pavements on a regular basis. On this project, after it had been under traffic for six months, there were several miles of it that showed a zero reading." A zero reading indicates the ride meter used to gauge the rideability of the pavement was unable to detect any roughness.
"The Mays meter [readings] were under six for the project," Anderson Columbia's McRae told ROADS & BRIDGES. "I understand that the project was the smoothest Georgia had ever recorded on a similar project." Marchant concurred, saying, "The project also had, to my knowledge, the lowest [meaning the best] overall readings of any project of this magnitude in the state."
According to Ken Murphy, Anderson Columbia's bituminous engineer, the Mays meter, used to determine the ride of the pavement, records more of what a motorist actually feels riding in a vehicle as opposed to a profilograph, which measures the difference in elevation between points. "The Mays meter is trailer mounted and records the movement of the body on the axle," he said.
Perhaps an even more impressive display of workmanship on the project lies in its appearance. According to McRae, in his comments about the project, the NAPA judge who evaluated the project said that the workmanship at the pavement joints was such that he had a difficult time locating them.
McRae credits the success of the project to the crew that worked on the project. "Mike Hudson, the paving foreman, did an exceptional job," he said. "He and his people really take pride in their work. The joints and the rideability really made for a super project." McRae added that while the Hayes Award is the company's first national honor, the company, and Hudson's crew in particular, has captured many regional and state awards.
Marchant gave kudos to Tony Williams, Anderson Columbia's area manager, and Hudson. "The paving crew was the best I ever worked with," he said. "Everybody in the company really cares about quality and it shows. The results were great. The job still looks good."
"We try on every job to go out and perform quality work, whether it's a county road, state highway or an interstate," McRae said. "It happened to work out that this job was abnormally good."
The project consisted of three main sections, milling and resurfacing, new lane, shoulder and guardrail additions, and overpass removal and grade lowering. According to McRae, a minimal amount of milling was necessary on the pavement, which consisted of asphalt laid over a concrete pavement. "The milling was performed to get the road back into uniform slope," he said.
The lanes were then overlaid with a 1 1/2-in. surface mix, topped with a 3/4-in. open-graded friction course (OGFC) designed to provide a smooth riding surface and reduce road spray in wet weather.
Building the two new lanes on soft Georgia clay delayed work on the project at times because of wet weather. A graded aggregate base material consisting of crushed lime rock was shipped in from Anderson Columbia's mine in Columbia City, Fla. A 3-in. HMA base was then paved over the aggregate base, followed by leveling courses where required, a 2-in. HMA binder course and a 11/2-in. surface course. The pavement was then topped off with a 3/4-in. OGFC.
OGFC impresses
The contractor was as impressed with the Georgia DOT's OGFC, as the Georgia DOT was with the contractor's work. Known in Georgia as a D-modified OGFC, the top course includes an SBS (styrene-butadiene-styrene) polymer modifier and reinforcing fibers. "It was the first time we've used the mix," said McRae. "We were really impressed with it. I thought it made an excellent riding surface. The texture was open and the drainage was good. All the published data says it will not close-up." According to McRae, Florida's experience with its OGFC had been that in time the course would close-up hindering the beneficial aspects of the mix.
"We knew from the start it was going to be a good mix," said Murphy. "We even brought up a Florida engineer to see it." Murphy is particularly impressed by the pavement's drainability. "It can be raining really hard and you won't even know it by looking at the pavement."
Anderson Columbia placed a test strip for the Florida DOT (FDOT) using the Georgia OGFC mix design and it was evaluated for skid resistance, hydroplaning and drainage. FDOT was so impressed with the mix that it is adopting the same basic OGFC design, called an FC5 mix, except the state is using ground tire rubber in place of a polymer modifier.
On the I-75 project, the mix contained 6% polymer-modified asphalt binder by weight of the total mix and 4/10th of 1% mineral fibers. The fibers, obtained from Fiberand Corp., South Miami, Fla., were blown into the mix.
During the project, the contractor faced another challenge when the original U.S. polymer-modifier manufacturer's plant burned. With all other U.S. manufacturers booked two to three years in advance, the company turned to a broker in Connecticut who was able to supply the project with Finaprene Vector 2411 SBS polymer modifier from a licensee in Taiwan. The modifier was purchased truck load by truck load and blended at the plant at 4.75% by weight of the binder by Advanced Asphalt Technologies, Sterling, Va.
According to Murphy, the OGFC course not only helps reduce spray, but the course, as it is applied in Georgia, also enhances the pavement ride. "Back in the late '70s, Federal Highways came out with OGFC, but it was put down real thin, about 1/2 in.," he said. "At that thickness it does nothing for rideability. At 3/4 in. thick, however, it does wonders for ride." He added that the OGFC also improves the safety aspects of the pavement, such as skid resistance and reduced hydroplaning.
Overpass removal
Removal of the overpass and lowering of the grade required a great deal of coordination because the work had to be performed in 180 days under traffic on the highway, which carried an ADT of 39,500. To conduct this portion of the project, three operations had to be staggered, according to McRae.
"We had to take out one side of the overpass, and while we were taking out the one side we ran traffic into a lowered median," he said. According to Anderson Columbia's Williams, the company cut down the median between the north- and south-bound lanes 14 ft and built a roadway detour through the median. "So the existing roads were actually higher than the detour," he said.
"After the first 30 ft of the overpass was removed, we encountered unsuitable material, which resulted in a change order," McRae said. "We had to bring in suitable material." In the end, the overpass was removed, the grade was lowered and the highway was built straight through where the railroad right of way had been. In addition to the overpass removal, another bridge also was reconstructed on the project.
