Reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) hold significant value with regard to the recycled binder and the recycled aggregate both of which can be incorporated into hot mix asphalt (HMA). Research on incorporating RAP and RAS into HMA has been conducted extensively and the methodology is to adjust the virgin aggregate gradation and amount of virgin binder to accommodate the portion of aggregate and binder contributed by waste materials. Specifications for recycled materials in HMA are based on the percentage weight of recycled materials by weight of total mix in HMA. However, limiting the percentage of recycled materials by total weight of the mix does not necessarily provide sufficient information on properties of blended binder.
In this research study, rheological testing was initially conducted on blended binders (RAP/RAS with virgin binder) using a dynamic shear rheometer and the results were compared to the properties of virgin binders. Limits on the amount of recycled binder in the blended binder were determined from blending charts to meet current Superpave specifications. These limits were used as the guideline for the Superpave mixture design procedure. Virgin mixtures and recycled mixtures were designed based on the recycled binder limits determined from the blending charts and each of these mixtures was tested on the asphalt mixture performance tester (AMPT) for measuring the dynamic modulus. The dynamic modulus was then used to estimate the fatigue and rutting life of each of the mixtures using a model pavement section in the AASHTOware Pavement M-E Design and was compared to the fatigue and rutting life of virgin HMA mixtures. Limits on the amounts of recycled binders were calculated based on the fatigue and rutting life of different mixtures and were then compared to the limits established from the blending charts. The lower of the two limits was selected for recommending a set of specifications for incorporating waste materials in HMA to the NCDOT.
