| To attain a good and reliable design and performance evaluation of AC pavements, the SuperpaveRTM mix design procedures as well as the newly released mechanistic-empirical pavement design guide (MEPDG) analyses require estimations of rheological properties of asphalt binders. The main objectives of this study were to evaluate local binders with and without different modifiers in the laboratory and predict the performance of the mixes.;To fulfill the objectives of this study, the SuperpaveRTM binder specification tests were conducted by using a rotational viscometer (RV), a dynamic shear rheometer (DSR), and a bending beam rheometer (BBR). The short-term and long-term aging of asphalt binders were simulated in the laboratory by using a rotational thin film oven (RTFO) and a pressure aging vessel, respectively. Non-specification binder tests related to shear-hardening/thinning behavior, and strain and frequency dependencies were conducted by using a dynamic mechanical analyzer (DMA). To ensure the repeatability of test results, at least three replicate samples were tested at each testing temperature or testing condition. The DMA used in this study was found to be an effective and useful alternative device to the DSR, especially in evaluating asphalt binders at very low temperatures (12.7°C or below). Because of the versatility of the DMA, it was found to be a valuable device for non-specification testing of asphalt binders.;One of the common distresses of hot mix asphalt (HMA) pavements is moisture-induced damage (i.e., stripping). To mitigate stripping in HMA pavements, liquid anti-stripping (AS) agents can be used. The current study evaluated the effects of different dosages of two commonly used liquid AS agents namely, AD-hereRTM HP (0.25%, 0.50%, and 0.75%) Plus and Perma-TacRTM Plus (0.50%, 0.75%, and 1.0%) on the rheological properties of a selected base (PG 64-22) binder. The maximum allowable dosage of either of these AS agents was found to be 0.5% (by the weight of the binder). The liquid AS agents were also found to reduce the rutting resistance of the base binder, but they did not adversely affect the PG grade of the binder.;The current study evaluates the effects of different dosages two selected WMA additives, namely AdveraRTM (4%, 6%, and 8%, by the weight of the binder) and SasobitRTM (1%, 2%, and 3%) on the viscosity and temperature susceptibility of the modified binder both at high and low service temperatures.;In regard to asphalt recycling, about 60 million tons of recycled asphalt pavement (RAP) materials were reused or recycled directly in the construction of new pavements in 2010. The usage of RAP was expected to be doubled by 2014 because of its beneficial effects in conserving raw materials and in realizing the goals of ongoing "green technology" initiatives. To this end, binders recovered from three RAP samples were evaluated. As expected, the recovered binders were found to be significantly stiffer than their virgin counterparts. Also, the prolonged use of the centrifuge and heat in the Abson recovery method was suspected to harden the binder. It was believed that the extra age-hardening, during the recovery process, caused the high PG and low PG temperatures of the recovered binder to increase up to 4°C and 3°C, respectively.;In conclusion, the current study evaluated rheological properties of asphalt binders modified with AS and WMA additives. It also evaluated binders recovered from RAP materials. Furthermore, an inventory of the MEDPG input parameters for local binders was developed. Finally, the evaluated rheological data were used to predict mixes' E* values, and estimate the sensitiveness of pavement distresses to binder type and source. The findings of the current study are expected to provide pavement professionals a better understanding of the rheological evaluation of unmodified and modified binders for pavement design applications. (Abstract shortened by UMI.)... |
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