Search

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]

Polymer modified asphalt (PMA) has been widely used in asphalt pavement due to its excellent mechanical properties. However most polymer modifiers are not specifically designed for asphalt modification, leading to issues such as incompatibility when blended with asphalt. Meanwhile, the rapid expansion of highway network has led to a growing diversity of demands for polymer modified asphalt, but it is quite challenging to persuade the refineries to adjust their polymers specifically for asphalt modification. Therefore, suppliers are increasingly turning to tailor the polymer modifiers themselves using screw extrusion. Screw extrusion is a manufacturing process that involves using a rotating screw to push the material through an extrusion head to achieve functions like blending, shaping or certain chemical reaction. It is widely used in the polymer field due to its versatility, continuous production capabilities and relatively lower cost. This paper aims to provide an overview of the application of screw extrusion process in the asphalt material field. Based on ingredients and processing purposes, the examined papers are categorized into six applications: i) Plastic compound; ii) Crumb Rubber (CR) compound; iii) Rapid-melting pellet; iv) Nanomaterial compound; v) Grafting; vi) Devulcanization of CR. Furthermore, summary and discussion on the compound formulas and extrusion parameters are provided. [ABSTRACT FROM AUTHOR]

Since the aged asphalt film coating Reclaimed Asphalt Pavement (RAP) aggregates has prevented virgin asphalt from directly attaching to the aggregates, the mechanism behavior developed between RAP aggregates and virgin asphalt should be considered differently. In order to directly measure bond strength between RAP aggregate and virgin binder, the Binder Bond Strength (BBS) test was performed, and artificial coated RAP substrates were prepared employing an innovative coating treatment. The aged asphalt film thickness and the aging level of RAP substrate, combined with dry and wet curing conditions were assessed regarding to their impact on bond strength. Fourier Transform Infrared (FTIR) spectroscopy was also utilized to investigate the effect of film thickness and aggregate type on aging properties. According to BBS test results, existence of aged asphalt film had positive effects on bond properties under dry conditions. Moisture weakened this enhancement and induced more debond at the diffusion zone where the aged film and virgin asphalt blend. A proper aging level may exist at which RAP can provide optimum bond properties. Moreover, through FTIR spectroscopy, a good correlation between oxidation and film thickness was observed. [ABSTRACT FROM AUTHOR]

• The fatigue performances of multiple representative modified asphalts are evaluated. • Three testing methods, namely time sweep, elastic recovery and LAS are compared. • Failure criterion should be carefully selected regarding modified asphalts. • LAS shows a better correlation with elastic recovery at increasing strain levels. • Elastic recovery may be a promising indicator of asphalt/mixture fatigue life. The fatigue cracking due to the repeated traffic loading is one of the main distresses that reduces the performance and service life of the asphalt pavements. The asphalt phase of asphalt mixture is the most critical for resisting fatigue damage, and thus it must be carefully evaluated for fatigue performance. Previous studies mainly focused on a limited range of asphalt materials while the applications of multiple new kinds of modified asphalts have surged in recent years. This study aimed to evaluate the fatigue resistance of 7 representative modified asphalts, including the linear SBS polymer modified asphalt, crumb rubber modified asphalt, terminal blend (TB) rubberized asphalt, EVA modified asphalt, Rock asphalt modified asphalt and bio oil modified asphalt. Three tests (times sweep test, LAS test and Elastic recovery test) and four different failure criterions are evaluated. Results suggested that elastomeric modified asphalts show the best fatigue performance, followed by non-elastomeric modified asphalts and plain asphalt. Elastomeric modified asphalts appear to show better fatigue resistance at higher strain level conditions. Also, the fatigue life of LAS test shows a good correlation with the elastic recovery, and the correlation improves with increasing strain levels. This suggests that elastic recovery could be a promising indicator for asphalt/mixture fatigue life characterization. [ABSTRACT FROM AUTHOR]

• A total of 18 field and laboratory aging conditions were assessed. • Much more sulfoxide is observed in field aged samples than laboratory aged ones. • R3.2% reduces with increasing testing temp while phase angle remains stable. • Polymer degradation causes more influence on the binder phase angle. • Asphalt oxidation causes more influence on the binder stiffness. High Content Polymer Modified Asphalt (HCPMA) can notably improve asphalt pavement performance. But Styrene–Butadiene–Styrene (SBS) polymer is sensitive to aging and its degradation significantly detriments the HCPMA engineering property, and thus it is of great importance to monitor the SBS degradation during the HCPMA aging. In this study, Attenuated Total Reflection Fourier Transform infrared spectroscopy (ATR-FTIR) was applied to characterize the SBS polymer degradation. A total of 17 lab/field aging conditions were considered. Infrared indices derived from spectrum semi-quantitatively analysis were correlated with binder rheology properties (G*, δ, Jnr3.2, R3.2). Results show that due to polymer degradation, HCMPA binder with a higher aging level generally has a higher stiffness with less elasticity. Moreover, HCPMA is vulnerable to high-temperature short-term aging and shows more resistance to the long-term aging at intermediate temperature. The applicability of standard laboratory bituminous aging, namely Rolling Thin Film Oven Aging (RTFO) and Pressure Vessel Aging (PAV), for HCPMA appears to be questionable. On one side, both RTFOT and PAV yield a much smaller aging degree than the actual HCPMA field aging. On the other side, significant sulfoxide generations are observed for field aged binders while RTFOT and PAV aging hardly generate any sulfoxide. Additionally, phase angle and R3.2% as two binder elasticity measurements were compared and they show different behaviors with increasing testing temperatures due to their different testing strains. [ABSTRACT FROM AUTHOR]

• Asphalt binder samples were collected from a practical HIR project. • The SBS asphalt binder aging during HIR process was investigated. • Extra aging caused by HIR was not as significant as expected. • The aging level of Bottom part is smaller than that of surface part. Hot in-place recycling (HIR) is considered as an effective way to reuse reclaimed asphalt pavement (RAP). Heating pavement is the core technology of HIR. To ensure construction workability, the pavement should be heated and held at a relatively high temperature. However, the high heating temperature of HIR may cause significant aging on the SBS modified asphalt, which is usually used in the pavement. The objective of this study is to understand the aging behavior of SBS modified asphalt in HIR and provide appropriate guidance for future HIR projects. In this research, eight kinds of asphalt binder samples were collected and extracted from different stages of a practical HIR project. They were then tested in terms of the chemical and rheological properties. The rheological properties of asphalt are evaluated by the frequency sweep testing and Multiple Stress Creep Recovery (MSCR) testing using the Dynamic Shear Rheometer (DSR). The chemical evolution during FTIR was tracked from Fourier Transform Infrared (FTIR) spectra and Gel Permeation Chromatography (GPC). The results of the experiments showed that the influence of long-term aging is quite significant and untreated pavement exhibits much lower elastic recovery due to the degradation of SBS polymer. HIR did cause some extent of extra aging to the treated pavement, Compared with Untreated, the Carbonyl index and molecular weight ratio of polymer of Heated (#3) are reduced by 34% and 39% respectively. The effect of heating gradient between different pavement depths is noticeable. The modulus of Surface is 2.69 times that of Bottom. The PB index of Surface is 0.37 times that of Bottom. There is no noticeable chemical reaction between the rejuvenator and the aged asphalt. After adding rejuvenator, the modulus of pavement decreased by 55%. [ABSTRACT FROM AUTHOR]

• A series of 16 types of rubberized asphalts is investigated. • A novel UTM bonding method is proposed. • A novel HWT analysis frame is proposed. • The effect of post-compaction, loading and moisture in HWT is separated. Extensive efforts have been devoted to recycling waste materials and reusing them in sustainable pavement. In this aspect, rubberized asphalt based on the waste truck tire is one of the most promising technologies. However, the moisture resistance of rubberized asphalt has always been a concern. This study attempts to investigate the moisture resistance of rubberized asphalt using two novel evaluation methods. From the asphalt binder aspect, a bonding energy indicator is derived from a novel universal tensile machine (UTM) bonding test to assess the direct bonding between the asphalt binder and the aggregate. As for mixture level, a new analysis frame is developed to separate the confounding effect in the Hamburg Wheel-Track (HWT) test, hence the influence of moisture can be exclusively quantified. For a comprehensive study, a series of 16 types of rubberized asphalts is investigated. Rubber content, rubber particle size, rubber particle type (sulfurized, desulfurized) and preparation temperature are considered. The results suggest that conventional bonding strength and TSR indicators cannot discriminate different types of rubberized asphalts and show a low correlation with each other (R2 = 0.01). Bonding energy indicator puts more weight on the toughness of rubberized asphalt and thus shows a fair good correlation with HWT performance (R2 = 0.48). The new HWT analysis frame further improves the correlation (R2 = 0.55). This validates the feasibility of using these new methods to quantify the bonding performance of rubberized asphalt. By adjusting the rubber content, particle size and preparing temperature, the bonding performance of the rubberized asphalt can be notably improved. [ABSTRACT FROM AUTHOR]

• Asphalt healing behavior in terms of bonding properties were studied. • CT scan was used to describe the macro healing process inside the asphalt material. • Bonding healing is a long-stand behavior after multiple bonding failures. • Water and polymer modification weakens the asphalt bonding healing potential. • Mastics exhibits better healing properties than binders at all healing conditions. Healing behavior of asphalt is crucial to the engineering performance of asphalt pavement and helps with extended service life. Therefore, the healing behavior of asphalt material has been widely investigated by extensive researchers. However, most studies focused on the evolution in asphalt modulus/stiffness and less attention was paid to the healing behavior in asphalt bonding properties. Even fewer researchers have discussed this topic at an asphalt mastic level. This study aims to evaluate the bonding healing behavior between the asphalt/aggregate interface using the bitumen bonding strength (BBS) test. Both asphalt binder and asphalt mastic were investigated. Numerous variables including healing time, healing temperature, presence of water, polymer modification and multiple healing cycles were discussed. Additionally, non-destructive X-ray Computed Tomography (CT) scan was conducted to visually confirm the macro healing process inside the asphalt material. Results suggest that bonding healing is a long-stand behavior, but after multiple fracture-healing cycles, the ultimate healing capability is quite low, especially for Styrene-Butadiene-Styrene polymer modified asphalt. Mastic samples exhibited improved healing properties than binder samples at all healing conditions. At a reasonable high curing temperature of 40 °C, base asphalt mastic shows nearly 100% recovery rate. Based on CT scan test, water and polymer modification weakens the asphalt healing ability while extended healing time and increased temperature is beneficial. [ABSTRACT FROM AUTHOR]