Field Evaluation of New Technologies for Measuring Pavement Quality (0-4774-2)

Traditional quality control testing of new pavement layers typically consists of localized random testing of layer density. In this process less than 1 percent or the pavement area is tested. In Project 0-4774, the focus in the second year of the project was to develop and evaluate two technologies, which provide close to 100 percent coverage of the section under construction. The first technology is instrumented rollers where an accelerometer is placed on the drum of a standard steel wheel vibratory roller. A prototype system was developed which can be mounted on any traditional vibratory roller. The complete system consists of an accelerometer, a distance-measuring device and specialized software for data acquisition, processing, and display. Field tests were conducted with this prototype unit, and it was demonstrated that the roller displacements are directly related to the quality of support of the foundation layer. Weak spots in the foundation layer can be detected with this system. The roller displacements were not correlated to the density measurements in the upper layers. The roller movements were correlated to traditional stiffness measuring systems such as the Dynamic Cone Penetrometer and Portable Falling Weight Deflectometer (FWD). The second technology is infrared testing to identify low temperature spots in newly placed layers of asphalt. A prototype infrared bar was evaluated in this project. The bar can be attached to the foot plate at the back of the paver. Specialized software displays in real time the temperature profile of the new asphalt layer. More field testing is recommended for both devices. For the infrared system a draft specification was developed for consideration of inclusion in TxDOT's Quality Control/Quality Assurance (QC/QA) program.