John D. Stephens knew he needed to increase the size of his equipment fleet when he started a recycling project in May at Atlanta’s Hartsfield-Jackson International Airport.
The president of Stephens Rock & Dirt was well aware of Doosan’s reputation and decided to demo an excavator.
He and his operators determined the machine was the right size for the job and came at the right price, so it became a permanent part of his fleet. But this one purchase soon led to Stephens buying seven more Doosan machines. He now owns six DX 420 excavators, two DX 480 excavators and a 130 excavator.
The crew of Stephens Rock & Dirt is working on familiar territory — it has been involved with airport projects for more than two decades and has become proficient in crushing, blending and moving massive amounts of material at Hartsfield-Jackson.
It’s the movement of material that’s different at this job site. More than four years ago, Stephens constructed a 4.5-mi.- (7.2 km) long conveyor system throughout the property that effectively moves material faster and at a lesser cost than conventional trucking. The company said the process has an efficiency rate of 99 percent.
The current recycling project consists of two sites. The first is a 15-acre (6 ha) section of a 100-acre (40 ha) parcel of airport property where recycled runway concrete is being crushed to 4 in. (10 cm) by a Lipman 3062 and blended with dirt for a 50/50 mix to be used as fill. The wire mesh in the slabs is extracted with a magnet in the crusher and also is sent off to be recycled. The minimal amount of wood at the site is ground up for mulch. The second site is a 350-acre (142 ha) tract just south of the airport and Interstate 285 that was purchased for fill material, which is transported to the job site by an over-land conveyor system.
In just nine days, more than 25,000 6-by-12-ft. (1.8 by 3.6 m) concrete slabs (each of which were 16-in. (41 cm) deep) were brought to the recycling site. They were stacked six deep and were butted up against each other.
Project Manager Joe Cantwell said this method of organization enabled the crew to better prepare the concrete to be broken down and eliminated the need for additional preparation.
The recycling process starts with the Doosan 420s, equipped with Kent KF45 hydraulic breakers, working on top of the piled-up concrete and breaking down one row at a time. The material is loaded onto articulated haulers by the Doosan DX480s and taken to the crusher.
In previous airport projects, Cantwell said concrete slabs were randomly dumped over a large area and crews had to ensure they were flat before they could perform their job.
He said the new stacking method has eliminated a lot of extra work and the need to pull 16-hour shifts for seven days a week.
To get the Doosan excavators atop the stacks to recycle from the top down, crews built a dirt ramp beside them. This enables easy access and allows the machines to come off the stacks for routine maintenance.
The recycling project will last for approximately two years. Cantwell said there are upcoming airport contracts to be let next year which will include bringing concrete to the recycling site.
“Some of the jobs that require our recycling process haven’t even been designed yet, but we already know the material will be shipped to this site,” Cantwell said.
The material the crew is currently recycling came from runway 8R-27L, an aging 10,500-ft. (3,200 m) runway that provided more than 200,000 cu. yds. (153,000 cu m) of concrete.
The runway closed Sept. 7 at midnight and crews from Gilbert Southern Co. started removing the concrete slabs. By 12:30 a.m., Cantwell said his workers started to receive the material. The final slab from the runway was brought to the recycling site Sept. 17.
The new runway was expected to be ready for air traffic Nov. 6.
The material from the runway will be part of the 4 million cu. yds. (3.06 million cu m) of recycled material to be used to fill 100 acres (40 ha) that may be the site of a new airport terminal in the future. The other material is crushed shot rock and boulders from the second site across Interstate 285. It is the same site that provided more than 16 million cu. yds. (12.2 million cu m) for the construction of the airport’s fifth runway, which was completed earlier this year.
Cantwell said the Doosan excavators have kept up with the fast-paced work well.
“We try to match the machine to the application, whether it be crushing or loading, to make for faster production, so there’s not a lot of idle time for them,” he said.
Stephens’ mechanics said the Doosans are similar to another manufacturer’s machines the contractor ran several years ago, so they are not having any problems with trouble-shooting.
Cantwell recalled one problem the mechanics couldn’t figure out, so they had their dealer, Crawler Equipment Sales, contact Doosan. Machine engineers were on the job site the next day.
“It turned out to be a simple connection that wasn’t making contact. It was a quick fix, but I can’t say enough about the outstanding immediate response,” he said.
Cantwell said parts come just as fast — either the same day or first thing the next morning directly from the Doosan warehouse. CEG Staff