There is considerable interest in the use of reclaimed asphalt in new asphalt concrete mixes used on airfield pavements, primarily due to cost savings and environmental benefits associated with substituting some of the virgin binder with the binder from the reclaimed asphalt. This report describes a study to determine the properties of these materials and the practicality of using them in new asphalt concrete on airfields. In laboratory tests conducted during this study, it was clear that although adding reclaimed asphalt to new mixes was likely to increase the stiffness of the mix (which in most instances was likely to improve the mix’s rutting resistance properties), its cracking resistance properties were likely to be reduced. Preliminary findings from this study indicated that the asphalt binder in recycled asphalt shingles may not effectively mobilize and blend with virgin asphalt and could reduce the actual effective binder content in the mix, which could in turn lead to early cracking and raveling. Test results on the properties of blended virgin and reclaimed asphalt binders can be influenced by the chemistry used to extract and recover the binders. Fine aggregate matrix mix testing is considered to be a potentially appropriate alternative procedure to evaluate the properties of blended asphalt binder in mixes containing reclaimed asphalt. Reclaimed asphalt should not be considered as a generic material with consistent properties, and some form of mix performance testing will need to be undertaken to assess the influence of the binder replacement on longer-term performance. The known benefits of adding polymer to asphalt binders may also be compromised if some of the virgin binder is replaced with reclaimed binder. This is particularly important in airfield pavements where polymer-modified binders are commonly used. The use of a softer virgin binder to compensate for the stiffening effect of high reclaimed asphalt pavement binder replacement rates (i.e., above 25%) appears to be justified.
DOT/FAA/TC-18/27
Authors: M.Z. Alavi, D. Jones, P. Chavez, and J. Harvey