Repeatability of Asphalt Strain Measurements under Falling Weight Deflectometer Loading

Embedded instrumentation has become an important tool at accelerated load facilities as states begin implementing mechanistic–empirical pavement design and analysis methodologies. Instrumentation can provide valuable information to help validate mechanistic models and develop a deeper understanding of pavement response under a wide range of conditions. Before these types of investigations are conducted, however, it is critical to determine if the response measurements are accurate and precise. Although both accuracy and precision are important, this investigation centers on establishing the practical level of within-gauge precision for asphalt strain measurements made at the National Center for Asphalt Technology Pavement test track. Ten test sections, each containing 12 strain gauges, were included in this study. Falling weight deflectometer testing was conducted on strain gauges, and the absolute differences were calculated to determine individual gauge variability. It was found that within-gauge variability was not significantly affected by gauge orientation, load level, or pavement condition. Overall, strain readings with differences less than 12 μ∈ were set as a practical benchmark for the test track for within-gauge variability. It is recommended that, as the sections continue to deteriorate, further testing be conducted to better quantify the relationship between variability and pavement distress.