Koss Construction
Koss Hits a Home Run in Western Kansas
EquipmentOverlay Concrete Update
KOSS HITS A HOME RUN IN WESTERN KANSAS Much of Interstate 70 in western Kansas had reached the end of its life. It was a full-depth asphalt pavement; sections ranged up to 20 inches deep. The most recent asphalt treatments had lasted just five to seven years, said Andrew Gisi, geotechnical engineer with the Kansas DOT. The state wanted something that would last longer, so they chose a 6-inch bonded concrete overlay -- 1.45 million square yards of it, to be exact. Last year, Koss Construction milled out 6 inches and slipformed two projects with concrete on 15.1 miles of four-lane interstate. Including shoulders, the two projects totaled 725,000 square yards and cost $20.1 million. This year, Koss will mill and pave two more similar projects on I-70 for a total of 727,000 square yards at a cost of $21.9 million.
KOSS’ SMOOTHNESS NUMBERS ARE SECOND TO NONE Koss’ smoothness numbers last year were remarkable. Using a Guntert & Zimmerman S850 Quadra four-track paver to pave 30 feet wide, the contractor averaged just 8.5 inches/mile on a zero blanking band over the two projects. What’s more, the MissouriKansas Chapter of the American Concrete Pavement Association (ACPA) gave Koss the “Smoothest Day Paving Award” for a 4,500 foot section on which the contractor hit just 5.4 inches of deviation. On every section of concrete pavement last year, Koss earned a smoothness incentive from the state.
In fact, to showcase Koss’ success and to demonstrate a large bonded concrete overlay project under construction, the MissouriKansas Chapter of ACPA hosted an open house last fall at the project. KDOT’s Gisi attended, as did representatives from most neighboring state transportation departments. The Colorado Department of Transportation is an especially important player in the Kansas situation, because KDOT used Colorado’s pavement design criteria and system in designing its 6 inch overlay on asphalt. The overlay is sawed into panels that are 6 feet square – and such overlays have provided Colorado with 10 to 12 good years on heavily traveled roads and remain in service. Gisi says that Kansas expects to get 20 years from the “6 X 6 X 6” overlay, possibly with some panel replacement at mid-life. “The road really needed reconstruction, but we couldn’t afford that,” says Gisi. “We get really good smoothness numbers everywhere we go,” said Robert Kennedy, quality control manager for Koss. “It is not uncommon for us to get single digits.” It is easier to achieve low smoothness numbers on the thinner 6 inch pavement, because the paver is not pushing a big head of material. “You can push the small head of mud and you are not extruding a lot of concrete either,” says Kennedy. Kennedy explained how Koss achieves such smooth-riding pavements. The contractor used dual stringlines. “We pay a lot of attention to the stringlines to make sure they are set up right. We make sure our paver is set up right and that our concrete batch plant
KOSS CELEBRATES 100 YEARS This year, Koss Construction will mark its 100th anniversary. It’s been a full century since second-generation German immigrant George W. Koss founded the company in 1912. Since then, Koss has grown to become one of the nation’s largest concrete pavement contractors. In the early twentieth century, nearly everything moved by rail, and George Koss saw a booming market in railroad bridge building. Soon his company, based in Des Moines, Iowa, was building some of the largest bridges in the country across 11 states. Koss has often done things in a big way. “When World War II broke out, the company went from a concrete pavement market defined by small projects for multitudes of owners to big paving job after big paving job for the military,” says David Howard, P.E., the current president and CEO of Koss Construction Co. “Some of these airfield contracts were unparalleled in size for that time – 500,000 to
is right. Then when we are confident that all of those things are set up, you have to be consistent,” says Kennedy. “The plant has to give you consistent slump on the concrete in every single batch after batch. And you have to have consistent delivery so that the paver never stops. Everything has to be in unison, working together.”
G&Z PLAYS AN IMPORTANT ROLE IN KOSS’ SUCCESS We asked Kennedy how he likes the Guntert & Zimmerman paver, “We own a couple of those, and we like them a lot,” he said. “I don’t see us as a company buying anything else. They are easy to set up, and easy to train people on. And Guntert gives us excellent service. If we need something, they are always available to us for parts or support. The Guntert paver gives us the smoothness numbers that you see. It’s a nice-looking finished surface.” On a good day, Kennedy said Koss paved one mile a day, working 30 feet wide. “We averaged about 1,800 square yards per hour, or maybe a little better,” says Kennedy. Two belt placers spread concrete in front of the paver, and that helped boost production. That way, Koss could dump two trucks at once. Each project last year had its own batch plant, and typically 15 trucks hauled concrete to the site. For nearly two miles of pavement last year, Koss paved with a stringless automated
George W. Koss
750,000 square-yard contracts were not unusual – and the company had to organize to pave every day to handle that volume of work. The scope of the company really changed at that point.” Then in the 1950’s, The Interstate Highway Program got underway. Koss Construction was recognized as the first contractor to enter into a contract under the Federal Aid Highway Act of 1956. Since then, large sections of Interstate highways across the Kansas, Missouri, Oklahoma and Iowa have been maintained or improved by Koss Construction. In 2011 Koss delivered just under two million square yards of concrete pavement. This year, the company will rebuild or rehabilitate almost 78 two-lane miles of Interstate highway, among other projects. Information for this sidebar came from Concrete Pavement Progress, published by the American Concrete Pavement Association.
control system from Leica Geosystems. The automatic paver control system bases its guidance on a digital terrain model – a digitized 3D model of the pavement – that is entered into a computer onboard the paver. The paver also has two prisms, mounted above the machine which provide a reference for the machine location for the two robotic total stations set up on tripods ahead of the paver. The prisms on the paver have a relation to points on the concrete paver’s pan. When setting up the two total stations, a technician back-sights each of them to known control points. That fixes the location of the total stations relative to the runway’s digital model. The total stations can then “see” two prisms on the paver and communicate to the paver – by free-wave radio – the paver’s precise location. The on-board computer then processes the differences between the actual paver location and the digital terrain model. Knowing those differences, the computer controls the paver pan location automatically. Koss used a total of three robotic total stations, and set two of them 250 feet in front of the paver. One robotic total station was
set behind. When the paver advanced close to the two forward stations, a technician would leapfrog the rear total station to a point up ahead. “The smoothness was good with the stringless system,” says Kennedy. “But those weren’t the two smoothest days we had. We were still learning the equipment. The guys were still on a learning curve. The crew liked the access to the equipment and they liked the access to the slab for finishing. But some of them have been paving for 20 years, and to not have that stringline to check grade was a little concerning for them.” Kennedy said one advantage to the milling and concrete overlay process was that Koss could correct roadway slopes and transitions into and out of curves. With so many asphalt treatments over 40 years, the slopes had gone awry. “We could go in there and pave back to the exact slope and correct all of those geometric issues,” Kennedy said.