Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85911
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. The changes in these critical factors are invisible to the roller operator during conventional compaction operations. The result is that either too little or too much compaction ef- fort may be applied to the pavement material, says the report. IC provides a better method because constant information is continually reported to the roller operator related to pass count, the in-place pavement material density levels, or other density-related properties such as material stiffness. "The second major shortcoming of conventional compac- tion equipment is that overcompaction can easily occur, and actually reduce the density that has already been obtained with previous passes," the authors say. "Overcompaction oc- curs when pavement materials that are already adequately compacted have one or more additional passes of a vibratory roller. When this occurs, displacement of the material does not occur and the vibratory roller can enter into the undesir- able 'double jump' mode where the roller is perceptively or imperceptibly bouncing on the pavement surface. This roller mode can be destructive to the pavement and actually cause a reduction in material density (and shear failure/dilation in soil materials)." It's also possible to undercompact pavements, they say. "This occurs when insufficient compactive effort is applied," they write. "IC would provide a better method to help the roller operator avoid overcompaction (and undercompaction) by providing continual feedback that allows the operator to obtain the optimum number of roller passes. IC is able to ad- dress both shortcomings in current QC methods by providing the roller operator and QC personnel with access to unprec- edented insight into the compaction process." The paper was based on the new Intelligent Compaction New IC tools available to contractors and agencies include onboard, color-coded displays, capability to measure underly- ing material support prior to paving, and capability to collect data for statistical analysis of the effectiveness of compaction operations. developed that is designed to manage and evaluate IC data. "This software is a great first step in addressing one of the biggest barriers to IC implementation, which is a myriad of is- sues related to handling the massive amount of data produced during the compaction process," the authors say. "The Veda software is available to the public." As part of the ICPF, a software program named Veda was "This software is a great first step in addressing one of the biggest barriers to IC implementation." A case study of the Wisconsin ICPF research was profiled to demonstrate how IC can improve QC of HMA paving. The project consisted of a two-lift HMA overlay on rubblized concrete pavements. Based on the ICPF findings, the authors concluded if IC had been used for the entire project, it could have: • provided a tool to evaluate the concrete pavement rubbliza tion process while it was underway, including the optimum degree of rubblization; • decreased variability in pavement density by improving the consistency of roller patterns during the HMA compac- tion operation by training the roller operator to use the onboard color-coded display; and Pooled Fund (ICPF) project, No. 954, Accelerated Implementa- tion of Intelligent Compaction Technology for Embankment Subgrade Soils, Aggregate Base, and Asphalt Pavement Materi- als, completed July 2011. The immediate benefits include: • real-time feedback to the roller operator, • permanent records of compaction data, • statistical and geospatial analysis of IC data, and • mapping of underlying materials prior to paving/compaction. • provided an independent analysis (separate from agency requirements) of quality by using Veda software to perform a statistical analysis of IC data. of IC technology, including the: • availability of equipment that meet the FHWA criteria of IC equipment, which includes GPS, intelligent compaction measurement values and temperature measurement; The authors maintain barriers remain to full implementation • complexity of data collection, management and analysis, in- cluding simplification, standardization of data, development Better Roads March 2012 19 Photo courtesy of: BOMAG USA