There are hundreds of thousands of acronyms in this old world, so it's a little incongruous but a lot apropos that the same acronym for an emergency procedure to restart a person's heart and breathing also applies to work that breathes new life into deteriorating roadways. And just as with cardiopulmonary resuscitation, Concrete Pavement Repair (CPR) has to be done right to provide extended life.
At work on a Nebraska Department of Roads (NDOR) project north of Lincoln, Ten Point Construction is performing CPR on seven miles of Highway 77, from Interstate 80 north to near Rock Creek Road. Working as a subcontractor to Safety Grooving and Grinding of Napoleon, Ohio, on the $1-million project, the Denison, Iowa-based contractor is repairing the concrete roadway ahead of diamond grinding to be done by the general. Ten Point's work, which began in mid-April and could be completed by the end of May, includes partial and full-depth patching as well as some cross-stitching on the divided four-lane highway. In addition, subdrains are being built on the shoulders for stormwater to exit from the base pavement.
"Diamond grinding is the thing of the future and right now Nebraska is real aggressive with it," said Ten Point Construction President K.R. Buck. "There are some roads out here that have a lot of life left in them and can be rehabbed. With most of these roads that they are doing the diamond grinding on, the repair work helps the road last another 15 to 20 years.
"It's called CPR, for concrete pavement repair, but it can also be referred to as CPR in that it does breathe life back into roads. A lot of states are doing this because we all know with the current funding situations that the budget isn't there to build a new road when a road is deteriorating so CPR is a cost-effective alternative for extending the life of roads that are still structurally sound.
"The biggest issue we're seeing recently is that the states have learned that they have to fix the roads completely before diamond grinding or they can have failures. Every patch, every joint needs to be repaired to make these diamond grinding jobs successful. We promote that and do the job right from the beginning so it does get the extended life they expect from the job."
"The two big reasons for projects like this are money and time," said NDOR Project Manager Babrak Niazi. "It's obviously much more economical and faster than repaving. Most of the concrete is in good shape on both sides so the roadway still has some life. In just a couple of months, we can make it serviceable for another 10 to 15 years."
Niazi said the project consists of several aspects: CPR partial and full-depth patching; installing subdrains; diamond grinding; and sealing cracks and joints. Engineers from NDOR's research department "sounded" the roadway with chains and balls to detect hollow or bad spots in the concrete and determine what repairs were needed. "With those methods, the sound is different in bad areas," he said. "They have the expertise to determine where the bad areas are and whether partial or full-depth patches are needed as well as the size of the patches."
The Highway 77 project requires about 1,200 square yards of full-depth patching and 250 square yards of partial patching.
"The concrete in the highway is 10 inches thick and for the full-depth patching, we are removing 10 inches and putting back 12 inches of concrete," said Jeremy Hildebrand, Ten Point Construction's project foreman. "The partial patches are generally about 2 feet square and we take out and replace about 5 inches of concrete on those."
On partial patches, Ten Point's crew uses saws and jackhammers to remove the concrete. They then clean the surfaces with air before adding a Type 2 epoxy grout for a good bond.
"On partials, we put the grout on the bottom and vertical faces except where we have a joint," Hildebrand explained. "On the joints we use a 1/2-inch Styrofoam bondbreaker."
The use of epoxy is an effort to prevent failures on the thinner partial patches. "This is the first job NDOR has required us to use epoxy and it makes sense," Buck said. "If there is 4 inches to 5 inches of concrete and you grind a 1/4-inch or 1/2-inch off, it's not surprising that you may have a failure. Using epoxy may help avoid that."
On the full-depth patches, no bondbreaker is used. Instead, the crew uses dowels to tie everything together. "We drill them, grout them in, put a grout protection disk over those, and grease them to allow it to slide," Hildebrand said.
In sections that require cross-stitching where there is a longitudinal crack with the traffic lane, the crew drills holes at a 35-degree angle, alternating every 2 feet. They drill 14 inches and install a 12-1/2-inch dowel bar with epoxy over it.
"The thinking behind that," said Hildebrand, "is that the bar will go in on one side of the crack and come out the other to hold it together."
In addition to the saws, jackhammers and drills (and the air compressors to power them), Ten Point's equipment on the job includes a Case 580 Super L backhoe loader and a Case 1845C skid-steer loader.
"This is one of our standard CPR setups as far as the equipment we have on the job," said Buck, whose company has three CPR crews and a flatwork crew. "We also run a Caterpillar PR105 milling machine on some of our patching projects, milling concrete and asphalt and putting either concrete or asphalt back."
A lot of CPR contractors don't have a skid steer on their projects, Buck said, but it is a major tool for Ten Point Construction because of its mobility.
"The skid steer is compact and mobile and we can use it for a lot of different tasks out here," Hildebrand added, "I wouldn't want to be without it. It saves us a lot of time loading out debris and in cleaning out and grading larger full-depth patches."
Depending on the weather, Ten Point planned to be finished with CPR on the project by June. Then, after the diamond grinding is complete, crews will seal the temperature (transverse) and construction (longitudinal) joints and any remaining cracks to prevent water from penetrating the pavement. The work done, Highway 77 will be ready for another 10 to 15 years of service.
"Nebraska has been very progressive with pavement repair and they have the mentality that if a road needs to be fixed, they will fix it," Buck said. "They also know that if there are some additional costs to make a project successful, like adding epoxy, that's what they will do. They don't cut corners when it comes to fixing these roads and I think they are getting their money's worth in extending the life of the roadway."