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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]

There have been many fracture tests – the Thermal Stress Restrained Specimen Test, the Single-Edge Notched Beam test, the Semi-Circular bend test, the Indirect Tensile Test and the Disc-Shaped Compact Tension (DCT) test – developed to understand thermal cracking in asphalt pavement. Among these tests, the DCT test is the most recent test method developed that has gained significant interest. This paper includes a laboratory study to measure the effect of different mixture design parameters on the DCT test results. The parameters include per cent binder replacement from recycled asphalt pavement, binder modification, low-temperature binder grade, oxidative ageing and mix design traffic level. To investigate the significance on the factors controlled, ANOVA and multi-linear regression analyses are used to show that only a few factors can be considered significant in terms of their effects on DCT parameters, and the significance of those factors could not explain the range in DCT response variables. Some of the trends in change in the DCT test responses with mixture ageing and some other factors are also found to be illogical. This paper does not offer solutions, but highlights some of the challenges experienced when applying the DCT test to performance specifications. [ABSTRACT FROM AUTHOR]

Most of the techniques used today to evaluate practically moisture damage in asphalt pavements are involved in compacted asphalt mixtures. These tests generally simulate field conditions, and provide a performance-related parameter of moisture effects by applying mechanical techniques. No test of the compacted mixtures, however, can isolate the fundamental and rheological properties of the asphalt-aggregate bond, which hinder proper understanding and quantification of the moisture damage phenomenon. To avoid these complications and improve the evaluation of asphalt-aggregate interfacial properties in moist situations, this study proposes a new experimental method. In this method, dynamic shear rheometer was used to measure asphalt-aggregate interfacial properties. A degree of moisture damage relating to the interfacial properties was then quantified using linear viscoelastic concepts to propose a meaningful parameter, called wet to dry yield shear stress ratio. Moreover, possible factors such as film thicknesses, conditioning times, and chemical effects were studied in terms of the W/D YSS ratio. [ABSTRACT FROM AUTHOR]

A field and laboratory study was carried out to study the effect of pressure and temperature on the compaction of asphalt pavements. Density, temperature, number of passes, and type of roller were recorded in the field at four different paving projects in Wisconsin, with binder and mixture samples obtained from each project. Compaction in the field occurred at temperatures that ranged from 125 to 60°C. Densification was achieved only for temperatures above the 70–80°C range. Roller contact pressures were estimated between 300 and 700 kPa during the compaction process. Laboratory compaction was performed with Superpave gyratory compactor using the field compaction temperatures and contact pressures. The lab compaction results confirmed that below a certain temperature limit densification decreased significantly. Binder testing was performed to determine the binder viscosities in the full range of field compaction temperatures observed. The upper limit of viscosity for significant reduction in densification was estimated to be 50 Pa s. A procedure for identifying the lowest temperature at which acceptable densification rate can be achieved is proposed based on testing using the dynamic shear rheometer. The determination of the lower temperature limit for compaction is an important task that is absent in the current specifications. [ABSTRACT FROM AUTHOR]

• Both binder rheology and mortar morphology analysis were conducted for RAP mixtures. • CT index of RAP mixtures can relate to the fatigue index of the asphalt and mortar thickness index. • Thicker mortar film can delay the aging-induced performance degrading of RAP mixtures. Fatigue cracking is an important pavement distress caused by repeated traffic loading that is known to be very sensitive to aging and climate conditions. A thorough understanding of the relationship between binder rheological and morphological characteristics and cracking resistance parameters of mixtures can contribute to the effective establishment of binder specifications. Therefore, this study aims to evaluate mortar film distribution and fatigue parameters of asphalt binder on fracture resistance of both virgin mixtures and recycled mixtures containing various softening oils and Reclaimed Asphalt Pavement (RAP). The mixtures were subjected to the short-term oven aging (4 h), long-term oven aging (8 h), and extended-term oven aging (16 h) using loose mix aging protocol at 135 °C. The mortar thickness was analyzed by using the 2D image from the sliced asphalt mixture samples. The statistical analysis was conducted to investigate the factors affecting the fracture performance of both asphalt binder and asphalt mixture. The results indicate the CT index of the mixture from the indirect tensile asphalt cracking test (IDEAL-CT) is significantly related to the parameters A and B of asphalt binder from linear amplitude sweep (LAS) test and the thickness of mortar. The mortar film thickness cannot judge the performance of the asphalt mixture alone. It is clearly shown in this study that thicker mortar film thickness within the RAP mixture can delay the weakening of fatigue fracture performance due to aging effect at intermediate temperature. The findings of this study might lead to a better cross-scale understanding of the fracture behavior of RAP mixtures. [ABSTRACT FROM AUTHOR]

Highlights: [•] HMABs had higher stiffness and elasticity than neat binder. [•] The asphalt layer thickness could be reduced by replacing neat binder with HMABs. [•] Mixing temperature of HMABs can be estimated by coarse aggregate absorption method. [•] HMABs had lower low temperature performance grades comparing to the base binder. [Copyright &y& Elsevier]

Thermal cracking is recognized as a critical failure mode for bituminous mixtures and good fracture properties are a key factor to obtain long lasting asphalt pavements in cold climate. Investigating this aspect in hot recycled mixtures with high amount of Reclaimed Asphalt Pavement (RAP) is fundamental due to the stiffening effect of aged bitumen that can emphasize the cracking aptitude of the mixture when subjected to thermal stresses. An innovative tool for characterizing the low-temperature cracking behavior of asphalt mixtures is the new developed Asphalt Thermal Cracking Analyzer (ATCA). It allows the evaluation of several parameters (e.g. glass transition temperature, coefficients of contraction, cracking temperature) directly related to the mechanics of low-temperature performance. In this study, four recycled asphalt mixtures were produced in laboratory with 40% of RAP using the Bailey Method as tool to optimize the aggregate structure. Different binder contents and modified bitumens (with various level of polymer modification) were employed. An additional mixture with 25% of RAP was used as control mixture. All the mixes were tested using the ATCA device. Moreover, an original image analysis was performed to assess at a microscale level the effects of compaction properties and aggregate structure on thermal cracking response. Results show that mixtures with 40% of RAP can behave better than the control mixture at low temperature if an accurate mix design is performed. Careful selection of RAP material and type and quantity of virgin bitumen can enhance low temperature performance and aggregate packing although high amount of RAP aggregates. [ABSTRACT FROM AUTHOR]