Air void content is a crucial parameter affecting long term pavement performance. Ground penetrating radar (GPR) offers a nondestructive method of determining relative asphalt air void content cheaply, quickly, and over an entire project. Previous implementations of GPR for the determination of air void content, including demonstrations as part of a recent SHRP2 study, were mostly positive, but suggested the need for a testing protocol. To explore various survey methodologies, a large-scale case study was conducted on U.S. HWY 52 in Minnesota using the rolling density meter (RDM), a commercially available device developed specifically for air void analysis in asphalt pavements. The lessons learned from the SHRP2 studies and initial Minnesota pilot projects were used on a full coverage trial implementation. The full coverage trial allowed for determination of the potential of the technology for improved QA/QC and resulted in development of best practice recommendations. This paper illustrates information provided by the full coverage data and outlines recommendations related to survey coverage, data file standardization and organization, verification of location and GPR measurements, and a rigid core collection procedure. The application of these recommendations allow an RDM crew to collect valuable relative compaction data for real time feedback without interfering with paving operations or traffic closures. Additionally, core calibration can be performed after surveying to convert data to air void content and project data analysis can be used to determine the construction practices most crucial to achieving sufficient compaction.
|Original language||English (US)|
|Title of host publication||Congress on Technical Advancement 2017|
|Subtitle of host publication||Construction and Forensic Engineering - Papers from Sessions of the 1st Congress on Technical Advancement|
|Editors||Jon E. Zufelt|
|Publisher||American Society of Civil Engineers (ASCE)|
|Number of pages||9|
|State||Published - Jan 1 2017|
|Event||1st Congress on Technical Advancement, CTA 2017: Construction and Forensic Engineering - Duluth, United States|
Duration: Sep 10 2017 → Sep 13 2017
|Name||Congress on Technical Advancement 2017: Construction and Forensic Engineering - Papers from Sessions of the 1st Congress on Technical Advancement|
|Other||1st Congress on Technical Advancement, CTA 2017: Construction and Forensic Engineering|
|Period||9/10/17 → 9/13/17|
Bibliographical noteFunding Information:
Various impulse radar versions of ground penetrating radar have shown that the dielectric properties determined from the asphalt surface reflection amplitude corresponds with core measured air void content [9-10]. Additionally, a step frequency array-based method improves the coverage and productivity of the measurements, making it an attractive alternative to current state-of-the-practice procedures . While these studies showed the potential of new technology for improved quality assurance in selected locations, the focus of this study is on how full coverage implementation following the final roller could be utilized on a construction project. In the case of the step-frequency array system , these technologies can require intensive data processing from the frequency domain or can be cost prohibitive, while the single impulse array systems [9-10] do not provide necessary coverage for widespread implementation. The method presented in this study is based on a system that evolved from recent research conducted under a National Academies of Science sponsored Strategic Highway Research Program (SHRP-2) . The GPR equipment used in this study is called the rolling density meter (RDM), which uses similar antenna to that presented in , but also applied in a 3 channel array to obtain some of the benefits in coverage explained in  where multiple antenna pairs are used in each pass.
© 2017 ASCE.