Sharif Digital Repository

Modeling the mechanical behavior of asphalt binders and mixtures has been the subject of intensified research in recent decades. Master curves of the norm of the complex modulus |G*| in the linear viscoelastic domain are frequently used for modeling, while phase angle master curves are less frequently considered for this purpose. Therefore in this research, an empirical model is introduced for phase angle master curves of modified and neat bituminous binders. The model is based on a general form of a double-logistic (DL) mathematical function. The |GG*| master curve was then modeled using a mutual relationship between the phase angle and |GG*|. Master curves of three neat and seven modified... 

In this research, Linear Amplitude Sweep (LAS) test was conducted on several asphalt binders modified by different percentages of gilsonite and Styrene-Butadiene-Styrene (SBS) polymer. Asphalt mixtures were also made from some of the study binders and tested for fatigue resistance using Four-point Bending Beam (FBB) fatigue test. The results showed that a strong correlation exists between LAS and FBB rankings at all the tested strain levels. Also, SHRP binder fatigue index (G∗sinδ), as a traditional binder fatigue index, was evaluated which did not show a strong correlation with either LAS or FBB tests. It was concluded that LAS test seems to be an effective binder fatigue test in predicting... 

Modified bitumen enhances the performance properties of asphalt mixtures. A number of studies in the last decade have evaluated the performance properties of modified binders at different service temperatures. It is however possible to evaluate some modified binder time-temperature characteristics and performance properties through their rheological master curves. In this research, styrene butadiene styrene, ethylene vinyl acetate, polyphosphoric acid and crumb rubber were used to modify a PG58-22 base binder. Rheological master curves for |G∗| and phase angles of these binders were generated using data from the dynamic shear rheometer and bending beam rheometer at temperatures ranging from... 

Master curves of asphalt binders and mixtures have been traditionally used to evaluate their rheological behavior in the linear viscoelastic range. Different analytical models are available to describe the master curves of bituminous binders and mixtures. No models are currently considered universal for all modeling purposes. In this research, the general structure and capabilities of some of the most commonly used analytical models were investigated. Then, based on the patterns of phase angle master curves of ten neat and modified asphalt binders, four groups of master curve shapes were defined. The goodness of fit of the models for the different groups of master curves was used to develop... 

One of the methods newly introduced in pavement technology to address environmental concerns and reduce total gas emission is warm mix asphalt (WMA) technology. In this study, polyethylene wax is used to produce WMA mixtures. Although this technology has several positive features, moisture and rutting resistance of WMA mixtures are always questionable. To evaluate moisture and rutting resistance of polyethylene-modified mixtures, indirect tensile strength and dynamic creep tests were used, respectively. Results indicated that polyethylene has positive effect at low compaction temperature on moisture resistance, and also has negative effect on rutting resistance  

Characterizing and modeling the fatigue performance of an asphalt binder is important when designing asphalt mixtures which can resist premature fatigue failure. Performance grading (PG) standards include the fatigue factor (G*.sinδ) to evaluate the fatigue resistance of asphalt binders. This criterion seems to be inaccurate, especially when applied to modified asphalt binders. American Association of State Highway and Transportation Officials (AASHTO) TP 101 has been designed to evaluate the fatigue resistance of asphalt binders using Schapery’s work potential theory. The damage evolution rate (α parameter) is the key element of this method and is calculated from the rheological properties... 

Asphalt Pavement Alliance (APA) created the Perpetual Pavement Award program in 2001. This program requires that the roadway has at least 35 years of service at the time of award and had experienced no structural failures. In addition, the program limits candidate roadways to those that have not received more than 100 mm of new asphalt nor have been resurfaced at a frequency exceeding 13 years. Minnesota Department of Transportation (MnDOT) currently owns the record for the most award winners and has received an award every year from 2002 through 2017. This study reviews all the award-winning roadways in Minnesota to determine common material, design factors and considerations which may have... 

Aged asphalt binder in reclaimed asphalt pavement (RAP) or recycled asphalt shingles (RAS) blends only partially with the virgin binder. To better understand this state of blending, the asphalt mixtures in this study were designed, mixed, and compacted using different RAP and RAS contents. The asphalt binders were extracted and recovered from RAP and RAS and then blended with different proportions of a virgin binder. The master curves for the asphalt mixtures and asphalt binder blends were then constructed from the measured data. A locally calibrated Hirsch model was developed to estimate master curves for the asphalt mixtures from the corresponding binder-blend data. Pairwise comparison of... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA field performance data is limited. This study investigated the susceptibility of Sasobit-modified WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using different concentrations of Sasobit and the... 

Incorporation of reclaimed asphalt pavement (RAP) and crumb rubber (CR) materials into asphalt mixtures have been of great importance from sustainability point of view. Although, inclusion of RAP materials in asphalt mixtures improves the rutting resistance at high temperature, the low temperature (LT) and intermediate temperature (IT) cracking performance of RAP mixtures may need additional considerations. In this regard, different schemes of modification have been applied to RAP mixtures to address its performance weaknesses. This study evaluated the effect of RAP and CR in combination with Sasobit and hydrated lime on the cracking performance of asphalt mixtures. The LT and IT...