Eureka!

Research that makes a difference

Intelligent compaction . . . application of reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA) . . . prefabricated bridges and pavements. They’re just a few of the themes of research papers presented at the 91st Transportation Research Board meeting in Washington, D.C., Jan. 23-27.

For the first time, registration reached 12,000 at TRB (www.trb.org), where delegates faced more than 4,000 peer-reviewed technical papers or poster presentations on transportation design, planning, construction, materials and operations.

Better Roads was there, and reviewed some of the new research potentially of significant value to readers.

Smart Rolling

Increasing benefits of intelligent compaction

Intelligent compaction (IC) of asphalt pavements is a powerful tool available to highway agencies that will help them ensure quality control, according to Robert D. Horan, P.E., The Asphalt Institute; George K. Chang, Ph.D., P.E., Qinwu Xu, Transtec Group; and Victor L. Gallivan, P.E., Federal Highway Administration (FHWA), in their paper, Improving Quality Control of Hot Mix Asphalt Paving Using Intelligent Compaction Technology.

Intelligent Compaction data may be viewed using overall project view, here viewed using Veda Software.

The authors posed the question, “Can existing intelligent compaction technology be used in a practical way to improve the quality control (QC) process for hot-mix asphalt (HMA) paving projects?” To find out, they investigated the use and benefits of IC technology for tandem-drum vibratory rollers used to construct HMA pavements.

The paper is based on the findings of the Intelligent Compaction Pooled Fund (ICPF) project that included 16 field demonstration projects in 12 participating states. “The ICPF projects were actual highway construction projects where various pavement materials were placed and compacted using both conventional compaction equipment, and rollers that were equipped with IC technology from various suppliers,” they say. Ten of the projects included placement and compaction of HMA, with IC used for only a portion of the project.

The authors define QC as the responsibility of the producer/contractor for testing, inspection and oversight of all of the materials and processes involved in a project, with the goal of ensuring a quality product that meets the specifications.

“Intelligent compaction is a maturing technology in the United States that provides beneficial QC tools during construction of HMA pavements,” the authors write. “These tools offer unprecedented information and capabilities that could revolutionize the compaction industry.”

On a tandem asphalt roller, automatic mat temperature sensing system (AMTSS) data can be logged with roller speed and vibrations per minute; these data can be stored as to the position on the mat using GPS.

Considered “intelligent” are tandem-drum rollers that are equipped with hardware such as an accelerometer, global positioning system, temperature sensors, an onboard computer, and software such as a real-time reporting system. Components of IC necessarily include GPS technology, accelerometer-based measurement systems and temperature readings.

“It is important to first have an understanding of the shortcomings of both the conventional compaction equipment and QC practices currently being used in order to comprehend the role that IC can take in improving QC of HMA paving,” say Horan, Chang, Xu and Gallivan. “First, there are shortcomings in the conventional compaction process itself. Conventional compaction equipment does not allow for any, or very little, ‘on-the-fly’ feedback to project personnel.”

Typically, using a standard vibratory roller, a fixed number of passes are applied to the material being compacted. The problem is that critical factors can vary during construction, including support from underlying materials, lift thickness, materials type and asphalt mat temperature, the authors write.