Repeatability of Asphalt Strain Measurements under Full-Scale Dynamic 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 such investigations are conducted, however, it is critical to determine whether the response measurements are accurate and precise. Although both accuracy and precision are important, this investigation centers on establishing the practical level of between-gauge precision for asphalt strain measurements made at the National Center for Asphalt Technology Pavement Test Track. Eleven test sections, each containing six paired gauges, were included in this study. Absolute differences between paired strain readings were computed on a per-truck and per-axle basis during 8 months of testing that included approximately 80,000 strain readings. It was found that longitudinal strain was slightly less variable between gauges than transverse strain. Steer axles had the least differences in strain between gauges, followed by the tandem and trailing single axles. The condition of the pavement (i.e., extent of cracking) was found to be very important to the measured differences between gauges. Overall, 80% of strain readings with differences less than 30 μ∈ were set as a practical benchmark for the test track