The impact of technology is evident in every industry and contractor Pace Construction, headquartered in St. Louis, Missouri, and seen it first hand. The company, which owns and operates four asphalt plants in Missouri, has an expertise in heavy and highway construction and asphalt production. Pace recently completed an asphalt paving job in rural Missouri where they utilized a new roller, the Volvo DD (Density Direct) 120C with Intelligent Compaction.
The Intelligent Compaction component aspect of the roller gives operators real-time insight into the work using pass mapping and temperature mapping. The easy access to detailed data allows the operator eliminate any destructive over-compaction and track density values using Intelligent Compaction with Density Direct. It collects working data (temperature, location, vibration data) and runs it through an ANN (Artificial Neuronal Network), a self-learning algorithm that analyzes this data and converts it into a clear and easy to read display of the estimated density over the full material surface.
The 28,000-pound roller has 148 horse power and a 79-inch rolling width. The roller provides pass mapping, temperature sensing and real-time density calculations over 100 percent of the mat. It enables the operator to know when target density is hit. It also includes a GPS for global position.
The rollers from the project were supplied to Pace by Cummings McGowan & West, Inc. (CMW) The St. Louis-based company supplies Midwest road builders and transportation departments with new and used equipment, rentals, and non-stop service and support. The two companies - CMW and Pace - have a longstanding relationship. Over the year, Pace has rented and purchased rollers from CMW and been supportive of their products.
Valuable Technical Support
Pace began renting the Volvo DD120C rollers in May, just a few weeks before the project in rural Missouri began. They've had smooth sailing with the roller. Brent Whitwell, a Materials Engineer for Pace who served as the Onsite Manager for the project, explains that CMW offered great technical support. While on site, Whitwell said of CMW, "They've had technical support here when we were testing the equipment. They've had representatives on site to help us and answer any questions we've had."
Jason Poor is a Construction Manager with Pace and works out of the company's West Plains, Missouri, office which houses the bridge and paving division. Poor was in charge of the project which utilized the rollers. The project, which ran for seven weeks this summer, was located in Summersville, Missouri, and ran along Route 17 toward Mountain View, Missouri on the North Section and picked up, after a short run on 17, down to West Plains, Missouri. The entire project was approximately 32 miles.
The 1-inch surface leveling project entailed going over an existing surface with nominally 1 inch of hot mix asphalt. The project incorporated the Intelligent Compaction specifications. The Missouri Department of Transportation (MoDot) is in a trial period on these rollers and has some project pilots going on. Most of those pilots are on projects with Superpave mixes.
"The project on Route 17 is one of the few that has surface leveling mixture and use on it," says Poor. "Surface leveling does not have a compaction spec, but we are utilizing the Intelligent Compaction roller to get sufficient coverage of the mat."
Project Goals and Challenges
On this project, there were 4.5 inches of existing asphalt on top of an older cold mix material that did not have much value left. The goal was to smooth out the asphalt and get the ruts out of it. The key, according to Poor was to get the proper amount of coverages. Poor notes you typically get eight to 10 years out of this type of job which for minor routes, "is good bang for the buck."
For this project, Pace was required by state specifications to do a test strip and three static passes. The purpose is to ensure the proper density. Attaining the right density can be a challenge. Poor says, "With superpave, you have to constantly monitor to ensure you are getting the right compaction. A slight change in the mix can lead to density problems."
The Volvo DD120C eliminated this problem. The roller's console is color coded to indicate density level. The operator knows which color he's shooting for to get him the compaction the project requires. Once he attains that color, he can feel confident that he has gotten the compaction level he was striving for. He can then migrate on down the road and know he has incentive pay on that section.
Whitwell explains that they were topping out at 89 percent density with three static passes with this mix. MoDot requested that Pace do a second test strip vibrating on very low amplitude, but they did not have a structure to roll against on the rural roads. "So, we did the lowest setting on the roller and that increased our density by 2 percent just by adding that one vibratory pass and two static passes," says Whitwell.
The increase in density translates into longevity on the road for MoDot. Anything to increase density and therefore longevity on the road with the same amount of effort enables MoDot to stretch their budget dollars even further.
GPS Aids Project
According to Whitwell, the project went very smoothly. For the IC portion of the project, the crew got to the site 30 minutes early and set up a Trimble base station and a 450 mega-hertz receiver radio. They transmitted data to the rollers for real time kinematic corrections, and the roller linked to the base station and radio. This allowed for increased precision on the GPS on the roller as they were not just relying on the overhead GPS satellites. They verified the rollers precision using a hand held rover every morning and then proceeded to pave and collect the boundary data as they paved each day.
Another project Pace has scheduled this year is an airport in Ava, Missouri. Whitwell notes that FAA projects typically have tighter specifications and lower tolerances on what is acceptable. He says, "We're looking forward to using this tech to help us dial in the density on that airport project." Poor adds, "We believe the Intelligent Compaction roller will benefit us there as well. It's a single 3-inch lift on aggregate based so getting the proper compaction will be very important since it's a single lift project there on that airport."
In fact, Poor notes, Pace's intention is to keep utilizing the Intelligent Compaction roller on the rest of their major highway projects for the rest of this year. He says, "We're very pleased with it. It's another to help monitor that we are getting the compaction we are supposed to get."
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