Using the physically based relationship between air void content and dielectric constant, the study also explored the potential of DPS or real-time compaction uniformity evaluation allowing the device to display measured dielectric constant in real time. This relationship indicates that HMA presenting lower or higher dielectric constant should have higher or lower air void content, respectively. In an example of this type of survey, air void content taken from cores at the same locations as the DPS measurements suggest a good correlation between the tests. In Figure 30, areas with higher dielectric constant locations indicate an adequate level of compaction while areas with lower dielectric values indicate insufficient compaction. The data forms a compaction map that provides real-time feedback to contractors and inspectors.
Core ID: W6 Low Core ID: W5 High Continuous Profile Allows Identification of High and Low Density Areas and Core Validation
5% Air Voids
10% Air Voids
Figure 30: Real-time data visualization and comparison with cores [63]
U.S. Route 1 Cherryfield, Maine This Maine DOT study was the first trial survey for DPS technology and was predominately for training proposes. The poor correlation between the DPS-measured dielectric constants and laboratory-measured air voids for one section were attributed to the lack of the 46
