Strain responses in ALF modified-binder pavement study

Twelve full-scale pavement sections were recently constructed at the Federal Highway Administration's Pavement Test Facility in Virginia to study the performance of Superpave mixtures containing modified asphalt binders. In order to evaluate the strain responses in the new sections (a key factor in pavement fatigue performance), 60 strain gauges were installed, five at the bottom of the hot-mix asphalt (HMA) layer in each of the 12 sections, during construction in the summer of 2002. The strain responses were measured in all 12 pavements under the moving wheel loading of two accelerated loading facility (ALF) machines early in 2003. Variables incorporated in the testing include: HMA layer thickness (100 and 150 mm), asphalt binder type (1 unmodified and 7 modified), load level (53 and 62 kN), loading speed (5 to 18 km/h), load offset distance (0, 150, and 300 mm), and pavement temperature (19 degrees C and 28 degrees C). In this paper, the measured strains are compared among the pavement sections to evaluate the effects of various experimental factors and as-built pavement properties. The variations in the measured strains were also examined. Based on the evaluation of the strain responses, additional tests are recommended for future study.