Evaluation of a Solvent-less Method for Estimating Asphalt Binder Properties of Recycled Asphalt Pavement
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Increasing amounts of Reclaimed Asphalt Pavement (RAP) are being used in response to the rising costs of asphalt materials. The asphalt paving industry currently lacks a method for characterizing the properties of the asphalt binder contained in the RAP which are necessary for proper design of asphalt mixtures utilizing RAP. The objective of this study was to develop a solvent-less method for determining high and intermediate-temperature properties of the asphalt binder in RAP. The candidate method chosen for evaluation was a torsional test performed on small bars of asphalt mix using the Dynamic Shear Rheometer (DSR) combined with the Hirsch model. This was believed to be a good candidate test due to the use of existing laboratory equipment, small sample size, and the fact that the test results were similar to those provided by other mixture and binder tests. The results of this study indicated that the torsion bar test showed promise for measuring the mixture stiffness of the RAP materials. The Hirsch model calculation showed promise for estimating the asphalt binder properties of the RAP materials but could not accurately estimate the asphalt binder properties of plant- or laboratory- produced mixes. The Hirsch model calculation also could not accurately estimate changes in the asphalt binder properties of these mixes due to increasing RAP content.