GOMACO World Index --- GOMACO World 27.3 - September 1999
An A+B contract for 4km (2.5 mi) of reconstruction on the Gene Snyder Freeway is adding up to some challenging paving conditions for its contractor. Gohmann Asphalt and Construction, Inc., based out of Clarksville, Indiana, is utilizing the Commander III's versatility to make this project work.
Preliminary work on the freeway, which is I-265 through Jefferson County, Kentucky, began in October of last year. As prime contractor on the project, Gohmann is responsible for all the grading, structures, and asphalt and concrete paving.
"It's basically a concrete overlay," said Joel Field, concrete paving division manager. "The existing highway is concrete pavement and we're putting an asphalt drainage blanket overlay on the existing pavement. Then we're placing 229mm (nine inches) of new concrete pavement on top of that."
The "basic concrete overlay" soon had a difficult element added to it. A change in traffic management created additional challenges.
The freeway carries a high traffic volume and within the 4km (2.5 mi) project area, Gohmann has to manage three interchanges and 16 ramps. All of them have to be kept open while maintaining traffic flow on the interstate at all times.
To deal with the traffic, the state of Kentucky originally proposed moving all the traffic to one side of the divided highway. With one side carrying all the traffic, Gohmann could pave the other side full width.
Usually that works, but once again, the complicated project required creative thinking to keep all the ramps and interchanges open.
"We went to the state to change the traffic scheme to what I call lane-at-a-time construction," said Field. "What enabled us to do that was the Commander III. It would allow us to pave in an area that is less than 610mm (24 in) wide between the edge of what we're paving and the temporary wall." The state accepted Gohmann's proposal.
The basic highway is two lanes, each 3.66m (12 ft) wide. In the median, there is a 1.22m (4 ft) shoulder and on the outside of the lane there is a 3.05m (10 ft) shoulder.
Gohmann is paving the 1.22m (4 ft) shoulder and the 3.66m (12 ft) slab together in one pass. The state of Kentucky requires a longitudinal joint between the two. A front mounted tie-bar inserter normally used on the larger GOMACO pavers was modified and offset mounted onto the four-track Commander III. Number five, 762mm (30 in) straight bars were mechanically placed on 610mm (24 in) centers to form the required joint.
Side bars or L-bars are being placed in the edge of the slab at the same time. The 762mm (30 in) long bars are bent at 90 degree angles and mechanically placed on 610mm (24 in) centers. Once again, the tie-bar inserter had to be modified.
"We have approximately 457mm (18 in) between the edge of what we're paving and the vertical wall," Field explained. "Essentially, we have a 381mm (15 in) bar laid into an 457mm (18 in) area outside of the slab that has to be pushed in."
A normal tie-bar inserter pushes the bar into the slab. Gohmann's inserter does just the opposite. The cylinder is mounted so as the cylinder retracts, it pulls the bar into the slab and allows the bar to be inserted despite the tight clearances. Without the modified inserter, the bars would have to be drilled and epoxied after the concrete had cured.
Due to the tight clearances, a special high-drive track was placed on the back of the Commander III. "As tight as we had to draw the leg in, a regular track's motor would have been sticking right into the slab," Field said. "With the high-drive track, the motor is basically sticking out above the slab."
Baskets are hand placed using Kentucky specs of 3.66, 3.96, 5.18 and 5.49m (12, 13, 17 & 18 ft) pattern averaging about 4.57m (15 ft) apart.
"We have to skip tie-bar insertion where the baskets are," Field explained. "We keep a man by each of the inserters so it's not a problem. We just have to pay attention."
Adding to the project's difficulties is an extreme deadline pressure, part of the A+B contract. The job has a contract completion date of November 15 of this year with either incentives or penalties depending on completion. "There's a $10,000 a day penalty for every day we go over the November 15 deadline," Field explained. "In addition, the number of days we wrote in for the permanent lane closures, every day we go over that there's a $25,000 penalty per day." There is no limit on the amount of penalties.
A maximum incentive of 5 percent of the total contract can be earned with early completion.
"It's one of those complicated big jobs where you have to maintain a lot of traffic while dealing with some extreme pressures to hit deadlines as well," Field explained.
A standard concrete mix design with type C fly ash and a water reducing admixture is being used on the project. Concrete slump is 44mm (1.75 in). Joints are sawed in every 4.57m (15 ft).
Gohmann has been averaging about 765m3 (1000 yd3) of concrete per day. "I think that's reasonable for the conditions, traffic, haul routes and tightness of the job," said Field.
The project is on schedule to be finished by the November 15 deadline. "I've got to give a lot of credit to the people I have in the field," explained Field. "Dennis Mayfield, general operations supervisor; Scott Fountain, paving crew supervisor; and Warren Vincent, set-up supervisor; all worked hard to make the pieces come together.
"But we couldn't have done the job without the Commander III," Field said. "I don't know of any other machine out there that could pave this job. Because of it, we went to the state and proposed a different traffic scheme and we knew we'd have these tight clearances. Again, it's just an 457mm (18 in) area and the Commander III worked in that tight area."
Gohmann Asphalt and Construction, Inc., was established in 1950. Specializing in highway and airport construction, the company has had on-going concrete paving operations for the last six years.