Koss Construction Performs Full-Depth Reclamation on I-70 in Northwest Kansas
New Initiatives Improve Performance: Scarcity of Materials Requires Creative Trucking and Storage Solutions for I-70 Pavement Replacement
In the 9-mile, $38.1 million pavement replacement project on Interstate 70 near Grainfield, Kansas, the Kansas Department of Transportation (KDOT) incorporated a number of new initiatives – including full-depth reclamation, permeability tests, and a different curing compound – designed to increase the long-term performance of the pavement.
The biggest challenge for prime contractor Koss Construction Co. of Topeka, Kansas, though, was overcoming the scarcity of aggregate and other road construction materials in northwest Kansas. To keep the project moving, they implemented creative trucking and storage solutions that ensured the materials were available when they needed them.
The three-year, federally funded I-70 project replaces asphalt pavement from the original interstate construction in the 1960s with new concrete pavement on all four lanes (two in each direction). Work also includes bridge reconstruction, new pavement at two rest areas, new right-of-way fencing, and lighting installations.
Koss built crossovers for the project in fall 2018, then in spring 2019 switched traffic to one lane in each direction on the westbound side of the interstate while they reconstructed the eastbound lanes. Over the winter, traffic returned to its normal configuration. In March, traffic switched head-to-head on the new eastbound pavement while crews reconstruct the westbound lanes. Work will finish by November.
Recycle in Place
According to Rob Percival, KDOT’s District 3 Construction Engineer, “Doing a full-depth reclamation on a project this big is fairly new to Kansas. Instead of removing all the existing pavement then bringing in subgrade and base material, we scoped this as an in-place recycle on the existing asphalt pavement, with the new concrete pavement placed on top of that.”
KDOT chose the full-depth reclamation because of economics, Percival said. “It saves aggregate, trucking, and other expenses, so it was cheaper per mile to do a recycle in place as opposed to our usual model.”
Koss previously performed full-depth reclamations in other states. For this project, “We mill off some of the asphalt to get the profile where it needs to be, then we incorporate cement into the remaining asphalt,” explained Bryan Fox, Koss’ Contract Management Director. “Because we go down 12 inches, we get into some soil product, too. Once we add the cement, it becomes a stable base to pave on.”
After they mix in the cement and some water, Koss’ subcontractor, Sporer Land Development of Oakley, Kansas, uses a Caterpillar RM800 Mixing Machine, similar to the equipment they use for traditional subgrade treatments, to prepare the base before placing the concrete pavement.
Trucks and More Trucks
Since suitable materials are scare around the project location, the cement comes from Pueblo, Colorado, 275 miles away. Koss chose a 1L cement (blended with limestone) because it was the most economical and sustainable.
Given the distance the cement travels, “We wanted to make sure we have enough to keep production going, so we’re using some big storage trailers – a total of eight to 10 cement pigs,” Fox said.
In addition, “We get our aggregate from 100 miles away, so there are lots of trucks coming and going,” Fox said. “It takes a lot of coordination.”
In fact, “Due to the volume of the project and its location, one of our biggest challenges was just getting all the materials secured and stockpiled,” Fox said. “We needed to procure 280,000 tons of sand and rock to make the concrete. We use a portable batch plant to make it all onsite, so we needed to start early.”
To make the process work, Koss formed some strategic partnerships with trucking companies. “The sand and rock come from an area that needs the grain grown here in northwest Kansas,” Fox explained. “We use the grain trucks to bring us our sand and rock, then they pick up a load of grain and take it back. It helps us economize the trucking since it’s so far away.”
New Tests and Technologies
To ensure the new pavement meets the latest performance standards, KDOT incorporated additional performance testing into the project.
“We’re doing a permeability test on cores taken from the pavement, which we haven’t done in the past,” Percival said. “We use the boil test, or volume of permeable voids, as one of the pay factors on this job. We also include the percent air of the concrete pavement in our pay factor for this project, where normally we just use the thickness and compressive strength.”
The new measures correspond to state and national goals, Percival said. “By using different tests to accept the pavement, we want to produce better-performing concrete pavement mixtures. We’re starting to re-evaluate the way we accept concrete mixtures, looking more closely at the air void system instead of just strength.”
For this project, KDOT also specified a new concrete curing compound, poly alpha-methylstyrene (PAMS), instead of a typical wax-based compound. “PAMS minimizes the moisture loss during the initial curing period and better protects the pavement from shrinkage and cracking,” Percival said. “There’s more solid material in there than our normal wax curing compound.”
Because PAMS goes on stickier than traditional curing compounds, Koss made some minor modifications to their procedures. “Since it’s a slicker material when you spray it on the fresh concrete, our saws just had to overcome some slipping, and we sometimes needed to clean our spray tips to keep them from gumming up,” Fox said.
For Koss, this is one of their first jobs using stringless technology. “Instead of our machines sensing off a stringline for vertical and horizontal alignment, we controlled our equipment with a total station system using a computer model,” Fox said. “It’s been much easier to construct because we don’t have stringline in the way; we don’t have to adjust it as it gets bumped or dropped for access in and out. Not having to set the string saved time and cost.”
As Koss reconstructs the four lanes of highway pavement, they also replaced a box structure that carries Gove County Road 62 underneath I-70. “The box structure was extremely deteriorated, so this project gave us an opportunity to remove the structure a half at a time and go back with a pair of span bridges (made from reinforced concrete) that provide more vertical and horizontal clearance for agricultural traffic crossing underneath I-70,” Percival said.