A micro surfacing application will generally extend a good road's serviceability for another seven years or so before an additional maintenance/preservation treatment is required.
Monarch executes the project
According to Steve Walenz, Monarch general manager, the project was originally let out for bid as two separate projects (northbound and southbound) and eventually combined and awarded in 2008. Due to weather and construction delays, the combined project was moved to the 2009 construction season.
The project called for a micro surfacing Type III (-3/8-inch aggregate) scratch coat to fill the ruts on the right travel lanes and a second micro surfacing Type III wearing course over both travel lanes, with a fog seal emulsion application on the adjacent shoulder asphalt.
"Rather than using individual rut boxes to apply the scratch coat, we used a 10-foot-wide box to provide a more consistent and level plane that is otherwise difficult to achieve with separate rut box passes over each rut," Walenz explains. "We had approximately 80 lane miles to pave with the final wearing course after we addressed the ruts with the scratch course on the right travel lanes."
Using a Bergkamp M1 paver, Monarch's micro surfacing paving crew of 25 completed the project in approximately 30 days.
"The road was in pretty good shape and only required some minor milling of some cracks where pavements were pushing together and bulging upward," explains Justin Arnold, construction manager overseeing the project.
The real challenge for Monarch was maintaining the stockpile of Type III aggregate it had staged in Cass County in 2008.
"Because weather conditions not only delayed this project but some of our other projects, we were not able to complete the work in 2008 as intended," Walenz explains. "That produced the additional challenge of maintaining the stockpile so the gradation stayed in tack, especially since the bottom two feet of the pile was under water during the spring flooding (2009 Red River)."
The only other unplanned challenge that had to be addressed once the project got underway was in removing the existing centerline stripe, which consisted of a material NDDOT did not think the micro surfacing application would adhere to.
"We had to make some scheduling adjustments once we got underway to accommodate other subcontractors, but since we produce the CSS (cationic slow-setting) emulsion used in the micro surfacing process, we were able to control when and how much to ship to our staging area in Cass County," Walenz states. "We used seven to eight nurse trucks to supply the paver since we were operating 20 miles or so from our staging area. We completed all the work within 28-30 days with single-lane closures during the day to apply the treatment and allow it to cure."
The total project required 12,000 tons of the Type III aggregate and 370,000 gallons of CSS-1H polymer-modified emulsion to complete the micro surfacing work, and approximately 63,000 gallons of HFMS-2 emulsified liquid asphalt to fog seal the 9.5-foot-wide outside shoulder and 3-foot-wide inside shoulder.
For NDDOT, the micro surfacing preservation approach used on I-29 provided the most cost-effective solution to address rutting issues, while delivering a safe and smooth ride for motorists who rely on that vital corridor. It's just one of many tools the road agency uses to keep good roads in good condition.