When it came to the Sitka Airport Project, contractor Knik Construction Co., Inc. (Knik) was looking at some tough specifications: milling ½ inch off the existing runway, paving 2½ inches on the milled surface, and using one Intelligent Compaction (IC) roller per paver. On top of this, the airport was closed nightly for construction to proceed from the hours of 7pm to 7am.
Knik used two standard FHWA specification Wirtgen/HAMM Tandem HD+ 140 VO IC Rollers in the breakdown rolling position. Onboard displays were used to monitor real-time pass counts and temperatures. The pass count feature played a dually useful role in the nighttime project; both pavers said that the pass counts made it possible to guarantee full coverage of the asphalt mat.
The IC rollers collected data during the Sitka Airport Project that helped the contractor save time and compelled Knik to keep the rollers for future use. At the close of each shift, IC data was collected, handled by the Quality Control Manager (QCM), viewed by Wirtgen/HAMM HCQ software, and then exported to Veda compatible files to share with the agency. Data collected included roller speed, frequency, and amplitude settings.
The IC rollers can help with another type of data collection, as well—asphalt density—though this specific data was not collected for the Sitka Airport Project. A few factors that contribute to asphalt density are: temperature, consistency of coverage, existing subgrade and base course density, rolling patterns, and variation mix. To properly collect data on density, pre-mapping of the surface must take place using the IC roller. This is done by making vibratory passes on a low amplitude setting over the existing surface to locate soft spots. Pre-mapping can help the contractor identify problem areas for repair; a tool Knik plans on utilizing in future projects.
Training took place on two fronts: roller operator and agency and/or contractor involved with IC operation. Wirtgen reps were on-site for training, providing one-on-one service to the QCM, and arriving before the start of paving, which allowed the contractor to utilize the equipment when the paving operation began.
In the beginning, the roller operators were not responsible for equipment or computer setup; however, after several days, roller operators were taught how to set up the computers. While at first unused to the onboard displays, both operators were able to read the data in a matter of hours. The data told the operators whether or not the asphalt mat had received the correct number of passes; a base number for the pass count was determined at the beginning of the project. After 1 week on the project, the roller operators were proficient in setting up the equipment and computer software.
STRENGTHS OF IC
IC can be used for various projects and can be a great asset to contractors. The real-time data pass counts collected with the GPS equipment eliminates the possibility of missing areas of asphalt mat during rolling, helping to achieve consistent densities. This is especially helpful during visually difficult times, such as night paving, as well as a useful tool for beginner roller operators.
Aside from pass counts, there is real-time data of asphalt temperatures. This is also a way to achieve uniform density. Existing pavement can be pre-mapped to check for weak spots or trouble areas. All roller settings from speed, frequency, and amplitude, to pass counts and temperatures are recorded so any issue can be ascertained by the data.
LIMITATIONS OF IC
As with every great technology there are a few drawbacks or limitations. IC is still fairly new and there are a few kinks that have yet to be worked out. The system has to be rebooted at times, which can be inconvenient to the contractor. Also, if there is no one tasked to data control when there is a large amount of data gathered during a project, going through the data can become unmanageable. This can be avoided if there is a person assigned to look at the data daily, however.
IC paving has distinct advantages in many types of paving sites and conditions, especially in hard to see conditions. The data collection helps create a longer lasting, solid state of paving with the help of pre-mapping to find weaknesses and soft spots in existing pavement. Adding an IC roller to the fleet would be a benefit to any construction company that performs significant amounts of paving work. The IC rollers are also good for training inexperienced roller operators, adding on yet another benefit. When taking into account the benefits of IC rollers, their ability to save time, money, and the data management, the machines seem like a win/win. ■
For More Information: Amanda Gilliland, QCM at Knik Construction Co., Inc., can be reached by email at firstname.lastname@example.org; Antonio Nieves Torres, construction engineer for the FHWA Office of Infrastructure Construction Management Team, can be reached by email at email@example.com; George K. Chang, PhD, PE, project manager at The Transtec Group, Inc., can be reached by email at .
Modern Contractor Solutions, June 2015
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