Driving down SH 13 today, it is hard to imagine that the span of road was once stricken by numerous signs of deterioration, but the Colorado Department of Transportation (CDOT) was able to restore the road back to pristine condition over the course of only five months.
SH 13, located in Rio Blanco and Moffat counties in Colorado, may be off the beaten path, but the rural route is a key link between I-80 to the north and mountainous I-70 to the south. So when CDOT noticed it was in need of some extensive repairs—soft spots, cracking and substructure failure—the agency selected Elam Construction of Grand Junction as the project contractor to get the job done with a $3.5 million contract budget.
Breaking it down
The multiple soft spots, which typically turn into gaping potholes if left untreated, and cracking were detrimental to motorists and needed to be targeted in a very specific way. Under the direction of Craig Area Manager Todd Combs and CDOT Engineer Randy Neece, the entire project was broken down into two sections to better target the specific repair needs of each area of road. The repairs varied in severity with the worst areas requiring workers to replace the road base, which Combs described as “bad subgrade.”
Site A, located in Rio Blanco County, north of Meeker, ran from approximately mile post 50.77 to 56.0. Site B was located in Moffat County, north of Craig Road, spanning from mile post 104.0 to 111.0.
The first phase of resurfacing began with Site B in May 2015 and also included vital safety improvements like guardrail repair and replacement. Site B was completed successfully, and crews moved on to the next phase, which was to tackle the numerous areas of deterioration smattered all along the road between Nine Mile and Craig roads.
“Basically you had the asphalt layer which varied in thickness, and right under the asphalt there were spots where there might have been an inch or two of road base and then just ran straight into mud. We actually hit a few soft spots where there was no road base,” Combs told Roads & Bridges.
Those issues, which could be described as an asphalt contractor’s worst nightmare, were handled swiftly and successfully by Elam Construction.
Due to the unique needs of the two project jobsites, Elam Construction employed two different milling techniques. The first half of the project, Site A, required a 2-in. mill and one 2-in. hot mix asphalt (HMA) layer.
“The repairs ran about 30 in. deep, but they were not full-width repairs, [more like] some 8-10-ft-wide spots,” Combs said.
According to Combs, crews milled out 2 in. and then put 2 in. back into the road. “Of course, there was a 2-in. top lift on that part, so where the milling was hitting the road, it caused a couple of rough areas, but those were really easily taken care of. It went really well. I think the 2-in. overlays are better than the 1.5-in. overlays. It makes for a better road.” Combs said.
“There were kind of two different deals with this. Site B was where we did the surgical repairs, which were basically soft spot repairs,” Combs continued. “Once that was completed, there were mill butt joints on both ends, which is typical for any overlay.”
Milled in a stepped fashion an inch or two at a time, as opposed to a sudden vertical joint, the mill butt joints aid in traffic maintenance as it allows passing cars during construction to not experience a sudden bump while driving over the joint.
The other half of the project, Site B, was a 1-in. leveling course with a 1.5-in. overlay. Combs acknowledged that a 1.5-in. overlay is a little bit more difficult to deal with because it’s thinner, “but nothing terrible.”
“There was a small area where they were going to do some leveling. They ended up doing pretty much the whole Site B with that 1-in. average, I would call it leveling, and then we did an 1.5-in. overlay over the top of that,” Combs said.
The road resurfacing repairs didn’t require full lane closures, since the repairs only spanned 8 to 10 ft wide. This worked out to better serve the commuting public as traffic was able to flow continuously at a reduced speed of 35 mph. Construction techniques such as employing mill butt joints during construction also made for a smooth ride during construction. Elam Construction crews also managed to complete the work all during daylight hours without the need for nighttime roadwork.
The paving process
In-house quality control technicians conducted multiple tests at the asphalt plant and during the paving process, including gradation, AC content, voids, VMA and compaction tests. Mat density averaged 92% with a 2% standard deviation. Crews also averaged less than 4% voids in the compacted asphalt.
A QC technician was present at the lab and at the jobsite to ensure crews were meeting specified density levels. A Weiler pickup machine was used to transport the HMA from the plant to the jobsite. The temperature of the asphalt at the plant was 305°F at the plant and 290°F when crews laid the mix down. Using a Caterpillar 1055D asphalt paver the asphalt was laid down and immediately compacted by one Caterpillar CBC64 and two Caterpillar CB54 rollers.
Crews completed a rolling pattern of two full vibratory passes, followed by two static passes and finished with static passes as needed to reach the 94% density mark at both sites.
Site A required a simultaneous milling and paving operation, which presented a challenge since work zones had to be short enough in order to not disrupt traffic. That aspect and additional coordination effort “took a little bit more work, but it wasn’t bad. It went pretty well,” Combs said.
Mother Nature plays nice
Asphalt pavements are susceptible to the thawing of the frozen subgrade during certain seasons, particularly in climates like Colorado when mositure levels can vary with the weather. Thawing weakens the subgrade and reduces support. But crews working on both sites of SH 13 “lucked out,” according to Combs, who credited the mild weather to the project’s success as it made for quick and manageable repairs.
A common challenge for high-altitude asphalt paving, especially in mountainous regions like Colorado, is that a higher rate of deterioration of roadways is prevalent in climates where the weather trends tend to fluctuate. Most asphalt pavements do not fail because of design factors such as thickness, but usually because of material problems or environmental distresses such as oxidation, thermal cracking and subgrade softening, as well as freeze-thaw damage, joint deterioration (spalling) and scaling during resurfacing.
Fortunately, crews did not experience those challenges due to a temperate climate. “We actually got really lucky. There were very few rainstorms. The weather cooperated well on this one,” Combs acknowledged.
With Mother Nature working in their favor as well as ongoing coordination and open communication between CDOT and Elam Construction, SH 13 in Rio Blanco and Moffat counties is now fully opened to traffic and offers a much smoother, safer ride. R&B
