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Using recycled materials in construction of asphalt pavements yields both economic and technical advantages. Recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) are two major sources to serve this purpose for which proper design and characterization are key elements. In this study, engineering properties of asphalt concrete containing RAP and RAS under dynamic loading were investigated. Three asphalt mixes were designed and included in this research: a conventional mix with no RAP/RAS as a control, a mix with 35% RAP, and finally a mix with 35% RAP and 5% RAS. A conventional resonant column (RC) apparatus was retrofitted and used for testing the specimens in torsional mode. Testing was conducted at five temperatures ranging from 10 to 45°C. Damping ratios and moduli of the mixes were analyzed and compared to assess the effect of the recycled materials on dynamic properties of asphalt concrete. Results clearly show the impact of RAP and RAS in increasing the mix stiffness. The study also included uniaxial dynamic modulus (DM) testing of the control mix to compare the moduli measured at high frequencies through RC testing to those estimated by the DM master curve through extrapolation. Results show that the modulus obtained from RC testing correlates well with that extrapolated from DM tests. Results also indicate that the accuracy of such correlation is significantly increased once dependency of Poisson's ratio on modulus is incorporated. [ABSTRACT FROM AUTHOR]

The falling weight deflectometer (FWD) testing develops a deflection basin on the pavement surface. Depths of this deflection basin from the center of the falling weight are measured at different radial offsets. These deflections are used for the backcalculation of the pavement layer moduli. Most of the available backcalculation software uses the layered elastic theory and static load to calculate moduli from known pavement surface deflections. However, the FWD test load is dynamic, and layer materials may show nonelastic behavior. Layered elastic theory in these types of software cannot characterize dynamic response of the pavement. Also, elastic theory is unable to accurately predict the surface deflection whenever stress developed in any pavement layer exceeds the yield point. For this reason, this study has performed a finite-element analysis of the airport pavement under the FWD test considering the dynamic load and materials plasticity. The analysis presented here includes elastoplastic behavior of pavement layer materials. Both axisymmetric and quarter cube models have been developed in ABAQUS. Time-deflection histories are simulated to match the FWD test data. A comparison is made between the dynamic, static, and field deflection basins. Contours of vertical deflection and strain are also plotted to observe their distribution on both the axisymmetric and quarter cube models. Analysis results show that the time-deflection histories are in close agreement with the field data. The axisymmetric model yields better results than the quarter cube model. Deflections from the static analysis are greater than the dynamic analysis for an identical set of the layer modulus of elasticity. A uniform distribution of strain is observed from the static analysis in both of the geometries. However, the dynamic analysis does not show similar distribution because of the time-dependent response. [ABSTRACT FROM AUTHOR]