Abstract
The concept of using a vibratory compactor as a tool for assessing construction quality by measuring the drum displacement with an accelerometer began decades ago. Initiated in Europe and correlated with plate bearing tests, this technology has advanced to “intelligent” compaction, in which feedback from the instrumentation can control the amplitude of vibration. With the national push to implement such methods in the United States, researchers at the Texas Transportation Institute sought to examine the relationship between the vibration amplitude of the roller drum and pavement layer properties on several Texas construction projects. Testing revealed that although the roller drum vibration amplitudes did relate to pavement layer properties, the correlation was with the stiffness of foundation layers, typically at least 12 in. below the surface. This finding presents at least one significant hurdle to implementing the instrumented–intelligent compaction concept: a change from density-based to stiffness-based specifications would be necessary. In addition, valid approaches to extracting properties of the surface layer are needed. The results from projects tested indicate that the most promising approaches to using this technology are for evaluating uniformity, compaction monitoring (determining when to stop rolling), and proof rolling. The proof rolling application requires validation to determine the depth of the weak spot.
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