Laboratory Performance Evaluation of Recycled Asphalt Binders with Differing Rejuvenators

Rheological and chemical characteristics of asphalt binders recycled using different recycling agents

Performance characteristics of asphalt binders modified with sunflower flour: A sustainable application of renewable resource derived material

This study investigated the influence of test temperature of the rolling thin film oven (RTFO) and pressure aging vessel (PAV) on aging of asphalt binders. It also evaluated the difference of three binders obtained at 85 and 100°C, as recommended by European and SHRP binder specifications for PAV, and at a typical pavement temperature of 60°C. The aging was evaluated in terms of the physical, chemical and rheological properties. Tests conducted included penetration, softening point, viscosity, mass loss, chemical compound analysis, infrared absorption spectrum (IR), gel permeation chromatography (GPC), bending beam rheometer (BBR) as well as dynamic shear rheometer (DSR). The results indicated that: (1) the hardness of the aged binders was sensitive to the RTFO test temperature, whereas, their Performance Grade (PG) was not affected; (2) increasing the PAV test temperature enhanced the oxidation aging, leading to significant changes in the properties; (3) the three aged binders obtained at PAV temperatures of 60, 85 and 100°C have insignificant difference in terms of the considered properties.

This study investigates the effectiveness of processed oil in the modification of PG 64-22 and PG 76-22 by assessing their physical and rheological properties, and multiple comparison was conducted between the two binders. The base binders PG 64-22 and PG 76-22 were blended with processed oil at four different percentages of contents (3%, 6%, 9% and 12% by the weight of the binder) and compared with the control binder in each test. The base and modified binders were artificially short-term and long-term aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were performed on the modified binders by applying a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). The comparisons and results presented in this study indicate that (1) the processed oil has a significant effect on the binders’ viscosity, which changes with respect to the increment of processed oil content. The viscosity of both modified binders decreased with the addition of 3, 6, 9 and 12% processed oil; (2) the performed DSR test showed that the addition of processed oil had a negative effect on the rutting resistance for both binders, since in PG 64-22, G*/Sin δ values decreased by 55, 65, 75 and 83% with the addition of 3, 6, 9 and 12% processed oil, respectively, while a decrement of G*/Sin δ of 24, 45, 58 and 65% with the addition of 3, 6, 9 and 12% processed oil was observed in PG 76-22; meanwhile, the fatigue cracking performance was improved and was found to be effective, while G* Sin δ in PG76-22 decreased by 9, 30, 36, and 52% and in PG 64-22 by 27, 44, 53, and 67% with the addition of 3, 6, 9 and 12% processed oil; (3) the results from the BBR test indicate significant improvement in the thermal cracking properties of the binders. The addition of 3, 6, 9 and 12% processed oil resulted in a decrease in the stiffness of both the PG 64-22 and PG 76-22 binders, with a positive effect consequently being observed on the m-values of the binders.

The current study aims to evaluate the viscosity and rheological properties of PG 64-22 modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil (PO) to enhance asphalt binder properties. Performance properties were measured at high, intermediate, and low temperatures. PG 64-22 was blended with SIS and Processed Oil at three levels (5%, 10%, and 15% by weight of binder) and two concentrations (6% and 12% by weight of binder), respectively. Modified binders underwent two short and long artificial aging processes, through the spinning of the thin film in an RTFO oven and a pressure aging vessel (PAV). The Superpave binder evaluations were carried out using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). According to the findings of the research, the addition of SIS caused higher values of viscosity, but when co-modified with processed oil, there was a substantial decrease in viscosity values. As a result, workability was improved. (1) It was observed that a greater reduction in viscosity was achieved when the processed oil was present at a higher concentration at 135 °C compared to a lower concentration. (2) The study showed that the incorporation of processed oil led to a reduction in rutting performance of the asphalt binder. However, the addition of SIS resulted in a notable enhancement of rutting resistance. (3) The role of processed oil as co-modifier at concentrations of 6% and 12% caused significant decreases in G*sin δ, based on the susceptibility of asphalt molecules to accept oil molecules in their network links. (4) The extracted measurements from the BBR tests indicated that modification with SIS and PO improved the low-temperature cracking resistance significantly. Comparison of asphalt binders modified with 6% and 12% PO and the same SIS content showed significant changes in modification with 12% PO rather than 6%.

The characterisation of asphalt binder at low temperature is of fundamental importance for selecting and designing asphalt materials with good and durable performance in regions experiencing severely cold climates. The current specification addresses this issue based on the Performance Grading (PG) system, developed during the Strategic Highway Research Program, and on low-temperature creep tests performed on asphalt binder with the Bending Beam Rheometer (BBR). Recently, an alternative experimental method was proposed to relate the complex modulus, obtained with the Dynamic Shear Rheometer (DSR) at low temperature, to the BBR creep stiffness. However, while DSR tests are performed in air, BBR relies on an ethanol bath for conditioning the binder specimens, making the relation between complex modulus and creep stiffness dependent on the specific cooling medium. In this paper, the effect of cooling medium on the low PG and on the rheological properties obtained from DSR and BBR tests is experimentally investigated and modelled. First, DSR and BBR tests, in ethanol and air, are performed on a set of different asphalt binders. Then, a relationship between the complex modulus in the time domain and the creep stiffness obtained both in ethanol and air is derived and the low PG for both cooling media is estimated. Finally, 2 Springs 2 Parabolic Elements 1 Dashpot and the Huet models are used to compare the effect of ethanol and air on the rheological properties of the asphalt binders. It is found that air results into higher creep stiffness and smaller m-values compared to ethanol. The two rheological models indicate that, only in the case of air, complex modulus and creep stiffness present the same kernel model parameters. This suggests that the low performance grade, obtained from BBR tests in ethanol, is strongly affected by the cooling medium, as well as the recently proposed procedure based on DSR tests. Based on the finding of the present research, the use of air for BBR creep tests is recommended.

With the increase in demand of flexible pavements, due to their various advantages over rigid pavements, there is a need to improve the aging properties of the bitumen in order to enhance its resistance against different types of distresses such as rutting, fatigue cracking. This research focus on the use of one polymeric additive Polyethylene (PE) and one non polymeric additive Sulphur (S) to enhance the aging resistance of asphalt. These modifiers are evaluated for their effect on the aging mechanism in comparison with the unmodified bitumen. Aging of the original and modified bitumen is realized by the Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV). Physical properties of the aged and unaged asphalt binders are evaluated through empirical testing like penetration, ductility and softening point test. Optimum content of the modifiers is obtained by comparing the results of conventional properties before and after aging. Fourier Transformed Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) are performed to bring out the chemical and morphological changes in the modified binder. Rheological properties of modified asphalt are evaluated with the help of a Dynamic Shear Rheometer (DSR). Results indicate improvement in physical properties of the modified asphalt even after the aging. Penetration index increased which shows less temperature susceptibility of the modified binders. Carbonyl and sulfoxide index are used as aging indicators which shows reduction in case of modified samples. Decrease in the sulfoxide and carbonyl index indicates better oxidation resistance of the modified samples. Morphological analysis proves good compatibility of the modifiers with asphalt binders. DSR results indicate improved viscoelastic properties of the modified binders. Hence it can be concluded that Polyethylene and Sulphur are good options to improve the aging resistance of asphalt in terms of their cost effectiveness and environment friendly nature.

This study presented the preparation and performance of a kind of high viscosity and elastic recovery asphalt (HVERA) by using some modifiers. The performance of styrene‐butadiene‐styrene (SBS), rock asphalt (RA), crumb rubber (CR), and stabilizing agent (SA) for different modifiers was investigated by conventional binder test. Effects of modifiers on the high‐ and low‐temperature properties of HVERA were investigated. The dynamic viscosity (DV) test, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) analysis indicated that the high‐ and low‐temperature rheological properties of asphalt were improved attribute to the addition of mixture of modifiers. Meanwhile, the short‐term aging and long‐term aging were simulated by rolling thin film oven (RTFO) and pressure aging vessel (PAV) tests. Furthermore, the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) measurements were conducted for obtaining the mechanism and microstructure distribution of the modified asphalt binders. From the test results in this study, it was evident that the addition of SBS, RA, CR, and SA into a neat asphalt binder could both significantly improve the viscosity of the binder at high temperature and lower the creep stiffness at low temperature, which was beneficial to better both high‐temperature stability and low‐temperature cracking resistance of asphalt pavements. It was proved that the high temperature grade of HVERA could be increased by increasing of RA and a proper percentage of modifiers could be improved by the low temperature grade of HVERA.

Effects of aging on rheological properties of asphalt materials and asphalt-filler interaction ability

Aging of asphalt binders is one of the main causes of its hardening, which negatively affects the cracking and fatigue resistance of asphalt binders. Understanding asphalt aging is crucial to improve the durability of asphalt pavements. In this regard, this study aims at understanding and differentiating the effect of temperature and oxygen uptake on the aging mechanisms of unmodified asphalt binders. For that, four laboratory aging procedures were employed. The two standardized procedures, rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), were considered to simulate the short-term and long-term aging of the asphalt binders, respectively. In addition, two thin-film aging test procedures, the nitrogen atmosphere oven aging test (NAAT) and ambient atmosphere oven aging test (OAAT) were employed to assess the effect of thermal and oxidative aging on unmodified asphalt binder properties. The NAAT procedure is based on the principle that the inert gas minimizes the oxidative aging. The rheological and chemical characterization showed that the high temperatures considered during the NAAT procedure did not change the properties of the unmodified asphalt binders. Therefore, it can be hypothesized that no significant thermal and oxidative aging was observed during NAAT aging procedure for the considered binders and that oxidative aging is the main cause for the hardening.

This research is aimed at investigating the mechanical behavior of the bitumen by the addition of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) obtained from waste plastic bottles and bags. Polymers (HDPE and LDPE) with percentages of 0%, 2%, 4%, and 6% in shredded form by weight of bitumen were used to evaluate the spectroscopic, structural, morphological, and rheological properties of polymer-modified binders. The rheological properties for different factors; viscosity (ἠ) from Rotational Viscometer (RV), rutting factor G*/Sin (δ), fatigue characteristics G*. Sin (δ), for the modified binder from dynamic shear rheometer (DSR), Short and long-term aging from rolling thin film oven (RTFO), and pressure aging vessel (PAV) was determined. The thermal characteristics, grain size, and texture of polymers for both LDPE and HDPE were found using bending beam rheometer (BBR) and X-ray diffraction (XRD), respectively. Fourier transform infrared (FTIR) analysis revealed the presence of polymer contents in the modified binder. Scanning electron microscopy (SEM) images revealed the presence of HDPE and LDPE particles on the surface of the binder. Creep Rate (m) and Stiffness (S) analysis in relationship with temperature showed a deduction in stress rate relaxation. Results have revealed the best rutting resistance for 6% HDPE. It also showed an improvement of 95.27% in G*/Sin (δ) which increased the performance of the bituminous mix. Similarly, the addition of 4% LDPE resulted in maximum dynamic viscosity irrespective of the temperatures. Moreover, fatigue resistance has shown a significant change with the HDPE and LDPE. The festinating features of waste plastic modified binder make it important to be used in the new construction of roads to address the high viscosity and mixing problems produced by plastic waste and to improve the performance of flexible pavements all over the world.

Different aging levels (RTFOT, PAV-10h, PAV-20h and PAV-30 h) of asphalt binders with various mass ratios of mineral powder to asphalt (0, 0.4, 0.8, 1.2, 1.6, 2.0) were used to investigate the rheological properties of aged asphalt binders with respect to their short and long terms aging characteristics. Viscosity test, dynamic shear test and creep test were conducted. The test results indicate that the viscosity of aged asphalt binder increases sharply with the extension of aging period. Complex shear modulus of aged asphalt increases, which indicates that the stiffness of asphalt binders can increase. The phase angle for aged asphalt binders reduces, which indicates that the elastic portion for viscoelastic property of asphalt binders increases. |G*|·sin δ increases after aging procedure which means that the fatigue resistance becomes poor. The creep test results show that creep strain curves varies remarkably for virgin and aged asphalt binders. The total strain during loading period and the permanent strain decreases significantly for aged asphalt binders, which implies that the elastic portion increases and the viscous portion decreases.

This study evaluated the aging characteristics of foamed warm mix asphalt (WMA) produced by water injection in comparison to traditional hot mix asphalt (HMA). Two asphalt binders (PG 70-22 and PG 64-22) and one aggregate (12.5-mm NMAS limestone aggregate) were used in this study. The short-term and long-term aging of the two asphalt binders were simulated using the rolling thin film oven (RTFO) and pressure aging vessel (PAV), respectively, while AASHTO’s standard practice for mixture conditioning for hot mix asphalt was used to simulate the short-term and long-term aging of the laboratory-prepared asphalt mixtures. The dynamic shear rheometer (DSR) was used to characterize the viscoelastic behavior of the original (unaged, RTFO-aged, and PAV-aged) and recovered asphalt binders; Fourier-transform infrared (FTIR) spectroscopy was used to identify and quantify the amount of functional groups present in the asphalt binders; and gel permeation chromatography (GPC) was used to determine the molecular ...

Asphalt with different aging degrees requires different rejuvenation methods. However, current applications of hot in-place recycling (HIR) for Reclaimed Asphalt Pavement (RAP) do not consider the differences in the aging degree of asphalt binder across different layers of RAP. Additionally, there is limited understanding of the changes in asphalt binder and aggregate properties during the HIR process. Changes in the properties of RAP materials can lead to inaccuracies in the mix design, potentially causing suboptimal performance. This study compares the performance of asphalt binders at different depths within RAP and clarifies the effects of the grinding and heating processes during HIR on both asphalt and aggregate properties. The aging gradient of RAP asphalt was assessed using macroscopic performance tests (bending beam rheometer (BBR), dynamic shear rheometer (DSR)) and microscopic techniques (scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR)). The effects of heating and milling on RAP materials were evaluated using conventional performance tests (DSR, BBR) and sieving analyses. The results show that the RAP asphalt exhibits an aging gradient under natural conditions, with the upper surface asphalt aging more than the lower layers. The heating process during HIR accelerates the secondary aging of RAP asphalt, reducing penetration by 25.3%, increasing the softening point by 7.4%, and decreasing ductility by 36.4%. The milling process causes gradation failure of RAP, with a damage rate of 14.4% of the coarse aggregates. Therefore, it is recommended that when using HIR for maintenance of severely aged pavements, the upper layer of the RAP should be separately milled and treated. The HIR mix design should consider the impact of heating and milling on RAP materials.

Preparation and rheological characterization of asphalt binders reinforced with layered silicate nanoparticles