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The current test methods for measuring the fatigue cracking resistance of asphalt mixtures involve many steps which are time-consuming and costly. On the other hand, asphalt binder testing is less time-consuming and more accessible than mixtures testing. Therefore, if the routinely measured properties of the asphalt binder and volumetric properties of the mixtures can be used to predict cracking resistance performance of mixtures, much effort to perform the mixtures testing of asphalt mixtures can be minimised. In this study, prediction models of mixture parameters calculated from the Semi-Circular Bending-Illinois Flexibility Index Test (SCB-IFIT) are developed using an experimental database including 42 mixtures that are short-term aged and 30 mixtures that are long-term aged mixtures. Based on the correlation results and the validation using a separate set of the mixture, the developed models of SCB parameters are found to provide reliable estimates of the flexibility index (FI), post-peak slope and fracture energy (Gf) of asphalt mixtures. The developed models are recommended for initial screening of mixture components (binder and mix variables) or estimating the cracking resistance of asphalt mixtures when testing is not feasible. They are not meant to totally replace the testing of the final selected mixtures. [ABSTRACT FROM AUTHOR]

The linear amplitude sweep (LAS) test is useful for evaluating the fatigue of asphalt binders. In this paper, the combined effects of strain and temperatures are investigated, and a method for estimating binder fatigue behaviour is introduced at different temperatures from limited measurements. LAS tests were conducted on several different PG-grade binders at four different temperatures. The results show that LAS parameters A and B at different temperatures maintain a linear relationship with the binder complex modulus (G*) measured at corresponding temperatures. Therefore, a fatigue life model, accounting for strain level and temperature, is proposed using a power function of the binder G*, which can account for temperature effects. To verify the model, its parameters are fitted using test data at two temperatures were used to predict the fatigue life at additional temperatures. This study findings offer a simpler and reliable method to predict the values of fatigue life at new temperatures using both 35% damage level and maximum stress failure criteria that are recommended in AASHTO TP101-12 and AASHTO TP101-14, respectively. The new prediction method will allow a wider use of the LAS procedure regarding the effects of temperature and strain level for which binders are subjected to the pavement. [ABSTRACT FROM AUTHOR]

Recently, there is a growing interest in increasing content of reclaimed asphalt pavement (RAP) material in the production of Hot Mix Asphalt (HMA) pavements to further reduce material costs and to preserve non-renewable resources. This study aims to evaluate the long-term performance of high RAP mixtures containing various softening oils. Both petroleum-based and bio-based oils were applied in preparing the 30% RAP and 50% RAP mixtures. The mixtures were subjected to the short-term oven aging (4 h), long-term oven aging (8 h), and extended-term aging (16 h) in the laboratory. Their performance, including the rutting, fatigue cracking at intermediate temperature, and low temperature cracking, were measured and compared with the control mixtures. The results indicate that the softening oils in this study can be used to produce asphalt mixtures containing high percentages of RAP with similar performance to a virgin mixture utilising the same aggregates and mixture design. In addition, the results show that making decisions to compare, qualify, or otherwise accept mixtures using the short-term aging results alone can be very risky. It is clearly shown in this study that relative ranking of mixture performance can change based on the level of aging. [ABSTRACT FROM AUTHOR]

Adding recycling oils (also called as 'recycling agents' or 'rejuvenators') into the asphalt mixtures with Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) is a widely adopted strategy for improving potential resistance to cracking of recycled asphalt pavements. This study investigates the rheolgoical properties of two Bio-Oils and two Re-refined Engine Oil Bottoms (REOB) by using Dynamic Shear Rheometer (DSR) and Rotational Viscometer (RV) tests at various testing conditions, as well as their chemical properties by using the Fourier Transform-Infrared Spectroscopy (FTIR) measurement. The results are compared for the recycling oils after the Rolling Thin-Film Oven (RTFO), 20- and 40-hours Pressure Aging Vessel (PAV) aging. Furthermore, these four recycling oils were blended with a base binder at a high ratio (50%) and measured for their complex shear modulus and viscosity at various aging levels, as well as their infrared spectra. At the end, two recycling oils were selected to blend with a base binder at low ratios (2.9% and 5.7%) and measured for the standard Performance Grade (PG) properties and PG plus characteristics. The results of oil-asphalt low ratio blends indicate that recycling oil's content plays an important role in aging behaviour of the binders, not only the type of recycling oils. [ABSTRACT FROM AUTHOR]

The film thickness of asphalt mortar, which is a mix of binder and fine mineral aggregates, has been considered as an important indicator for assessing the durability of asphalt mixture. This study proposes a novel method to characterise distribution of mortar film thickness in asphalt mixture through image processing techniques. Four asphalt mixtures with unmodified and modified binders were produced at various compaction temperatures in the laboratory. Their internal images were scanned and analysed. The values of mortar film thickness along the boundary of each aggregate in the scanned image were measured. And their mean value (Tm) and standard deviation (SDt) were calculated for characterising the distribution of mortar film thickness. The results indicate that both binder modification and compaction temperature have significant effects on the mortar film distribution. Furthermore, the proposed parameters were employed for understanding the correlation between the mortar film thickness and mixture cracking resistance. The flexibility index of short-term and long-term aged mixtures were measured and correlated with the mortar film parameters. The findings show that asphalt mixture with a lower mortar film thickness and a wider distribution is more sensitive to oxidative aging, which may result in a dramatic decrease of mixture's resistance to cracking. [ABSTRACT FROM AUTHOR]