New Technologies for Evaluating Flexible Pavement Construction: Year 1 Report

Historically in Texas, acceptance of flexible pavement layers has been based upon density control, where the density of the layer must meet or exceed some minimum value. The Texas Department of Transportation (TxDOT) utilizes the nuclear density gauge to perform this acceptance testing for sub grade and base layers. However, TxDOT desires to find a non-nuclear method for measuring density; additionally, TxDOT desires to investigate the feasibility of a fundamental shift from density to mechanistic properties for acceptance. This report describes the search for a replacement for the nuclear gauge and also summarizes new techniques that could potentially be used for acceptance of flexible pavement construction. Currently no direct replacement exists for the nuclear density gauge; the most similar devices are the Pavement Quality Indicator and the Pavetracker Plus. However, these two devices are only applicable to hot-mix asphalt layers and are best suited for measuring differential density. Several systems exist that are not density-based that potentially could control flexible pavement construction. These systems include the Vertek and AquaPro moisture probes, the portable falling weight deflectometer, the dynamic cone penetrometer, instrumented vibratory rollers, automated proof rollers, ground-penetrating radar, and infrared imaging. The latter four systems provide near 100 percent coverage and could serve as screening tools to identify where to perform spot tests. This report describes preliminary testing of the most promising systems and outlines a framework for continued testing with the most promising devices for use during the remainder of this project.