Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/325401
12 June 2014 Better Roads Applications & Innovations "At that time, even the most optimistic designer could not have envisioned the growth in traffic that would take place on this rural interstate," says John Roberts, executive director of the International Grooving & Grinding Association (IGGA). "However, during the past 40 years, the roadway has become not only a popular commuter route during the business week, but also a heavily trafficked roadway during the weekend when residents return to their homes from their lake cabins." According to early 2013 reports, traffic had reached capac- ity at 28,500 vehicles per day with about 13 percent of vehi- cles being trucks. With such heavy use, the ride quality of the surface began to suffer due to the original designer's choice of load-transfer devices, which were 1-inch black steel dowels with no epoxy coating. The current common practice calls for 1-1/2-inch diameter dowels with a thick epoxy coating. As early as 2004, these dowels had rusted and were no lon- ger functioning, which reduced the pavement's load transfer efficiency between slabs. Minor faulting (less than 1/4 inch) was noticeable in the truck lane. In 2006, the District tried micro-surfacing on 23 miles in order to improve the ride. While this treatment briefly improved ride quality, it did not solve the load-transfer problem. A toolbox of repair options By 2009, MnDOT District 3 Engineer Dan Anderson chal- lenged his staff to develop better solutions to the faulting problem. Frentress says Anderson realized he needed to identify a mix of repair techniques with different expected design lives while simultaneously looking for innovative CPR ideas. Using ARRA funding, the District began the interstate's overhaul with a concrete repair project on about 40 miles of the original 65-mile stretch of I-94. Many concrete pavement preservation treatments were used to rehabilitate the surface, including full- and partial-depth repair with diamond grind- ing. Due to monetary constraints, the district was not able to replace the load transfer at every joint, so faulting was expect- ed to return. The project was completed with minimal disrup- tion to the traveling public, primarily using night closures. Despite the overall success of the rehabilitated concrete pavement, by 2012, minor faulting had returned but only in the truck lane. For the 2013 construction season, District 3 let two concrete projects on I-94. One involved a concrete over- lay approach on 14 miles of the 25 miles of concrete remain- ing to be fixed. This was let as an accelerated project with the reconstructed eastbound lanes required to be open for Memorial Day traf- fic on May 23, 2013. The roadway repairs were completed on schedule by that date, with final completion for the second lane of construction on July 26, 2013. The total cost for this project was $1,176,647 per mile. The concrete pavement items totaled $525,680 per mile. Although the concrete overlay is expected to provide the longest-term fix of at least 40 years, having the I-94 traffic restricted to one lane in each direction during construction of the overlay was difficult for the public. The District planned for the second concrete project to be completed only at night and have both lanes open for rush hour traffic each day. For this section of pavement, the repair method known as "Buried Treasure" was chosen – a method referred to as such because non-destructive testing tools allow for the collection of enough information on underlying payments to determine which ones can be exposed and repaired and thereby con- tinue to provide service life. The project called for the removal of the micro surfacing that was placed on I-94 in 2006 and replacement of every joint and crack with a full-depth repair was discussed by the design engineers. Pavement evaluation revealed only 5 percent of all pavement cracks were occurring at mid-panel locations. It was clear that lack of load transfer was at the heart of the faulting issue. MnDOT then realized that an effective solution would be to replace all the transverse joints and cracked slabs using full depth repair. An initial project was scheduled, along a 10-mile section of the westbound lane and 1.2 miles of the eastbound lane of I-94. This solution was able to meet the required 20-year design life and be constructed under traffic. Here's a view of skewed full-depth repairs after removal of the microsurfacing and 6 feet of diamond grinding. A&I_BR0614.indd 12 6/2/14 9:56 AM