Aged Asphalt Mixtures Research Articles

An Active Anti-Aging Technology for Asphalt Mixture

For aged asphalt, as the content of light component gets smaller with the passing of time, the performance of the asphalt mixture would degrade accordingly. This study aims to develop an anti-aging material that can supplement light component to asphalt pavement during its service process, thereby suppressing the aging of asphalt and prolong the service life of the road surface. At first, this study carried out four-component separation test to measure the loss mass of light component; then in the experiment, the oil shale wastes were impregnated in light component to determine its adsorption capacity to the light component. After that, according to the loss of asphalt light component after long-term aging and the adsorption ratio of anti-aging materials with different particle sizes for light component, the amount of anti-aging material to be added was determined; moreover, via rutting test, beam bending test, and freeze-thaw splitting test, the high-temperature stability, low-temperature crack resistance, and water stability of the asphalt mixture modified by the proposed anti-aging material had been verified, and the results proved that the proposed anti-aging material can well suppress the aging of asphalt mixture.

The Combined Effect of Ultraviolet Irradiation and Temperature on Hot Mix Asphalt Mixture Aging

Reliable accelerated simulation of asphalt aging is of significant interest to asphalt researchers and pavement practitioners alike. However, current laboratory aging protocols are either based on binder aging rather than mixture aging or use dry ovens to heat asphalt mixtures, omitting the important effects of UV radiation. Binder aging cannot take into account the interactions between the binder and aggregate phases during aging, while the omission of UV radiation ignores an important catalyst in the aging process. In this study, a comparison of the effect of conventional thermal oven aging to the combined effect of heat and ultraviolet irradiation on the resilient modulus and surface texture of dense-graded asphalt field cores and gyratory-compacted samples was undertaken. Significantly higher rates of modulus increase with aging time were measured for the samples aged by both heat and ultraviolet irradiation. The gyratory-compacted samples showed more realistic results in terms of surface texture compared to the field cores, likely due to the extraction of field cores from a small area of pavement that was subjected to concentrated pneumatic tyre rolling, which was not representative of typical asphalt construction. It was concluded that using aging indices, calculated as the ratio of the aged value to the initial value, is recommended for asphalt aging investigations. The findings of this study highlight the significance and importance of developing aging protocols that combine heat, ultraviolet irradiation, and any other environmental factors that may affect the aging behaviour of asphalt mixtures.

Stiffness Modulus of Aged Asphalt Mixtures

Asphalt mixtures have a dominant position in road construction in most countries. The choice of asphalt mixture type and surface depends mainly on the traffic loading and climatic conditions. The stiffness of asphalt mixture is one of important parameters that determines how road pavement performs and what pavement response to traffic loading. The stiffness modulus of the asphalt mixture changes during its service life, it tends to increase. During this process the mixtures in pavement age and degrade. Aging of asphalt mixtures has a significant effect on changes in the properties of individual mixtures. Presented research was focused on monitoring the change in the stiffness modulus of two asphalt mixtures AC11 50/70 and AC11 PMB 45/80-75 by the effect of aging. The asphalt mixtures have been exposed to the effects of short-term and long-term ageing by the conditioning of loose mixture method. After aging of the asphalt mixtures, the stiffness modulus of compacted asphalt mixture samples was measured. The stiffness modulus was determined using the IT-CY method at temperature of 10 °C, 20 °C and 30 °C and showed an increase after exposure of the mixture to short-term and long-term aging.

Fatigue Properties of Aged Porous Asphalt Mixtures with an Epoxy Asphalt Binder

Porous asphalt pavement has been used for multiple purposes, but its large porosity makes it easy to age by long-term weathering conditions; this causes its premature failure through raveling, fatigue, and so forth. This study explored the fatigue performance of aged porous asphalt mixtures produced with epoxy asphalt binders. Gradations of three porous asphalt mixtures were first designed in the laboratory: (1) a porous asphalt mixture 13 with an epoxy asphalt binder (EPA-13); (2) a porous asphalt mixture 13 with a high-viscosity asphalt binder (HPA-13) as a control; and (3) a dense-graded asphalt mixture 13 with a high-viscosity asphalt binder (HDA-13) as another control. Then, fatigue tests were conducted under different strain levels on porous asphalt mixture samples before and after aging. In addition, the effect of loading sequence on fatigue was examined for samples under two-stage continuous loading conditions. The results showed the following three things. First, the use of epoxy asphalt binder can tremendously improve the fatigue resistance of porous mixtures. the fatigue life of EPA-13 was 2.0 to 4.5 times greater than that of HPA-13, depending on the strain level. Second, after long-term aging, the fatigue life of the EPA-13 subjected long-term aging decreased by 82.3%. The retention rate of the initial modulus was about 50%. The fatigue life of the weathered EPA-13 was still much better than that of the weathered HPA-13. Third, loading sequence had a remarkable influence on the damage accumulation of all mixtures discussed.

Chemical and Rheological Characterization of Asphalt Binders: A Comparison of Asphalt Binder Aging and Asphalt Mixture Aging

The objective of this study was to compare the chemical and rheological properties of asphalt binders recovered from aged asphalt mixtures with the corresponding aged asphalt binders used in those mixtures. Seven plant-produced asphalt mixtures, with unmodified and polymer modified asphalt binders and varying reclaimed asphalt pavement (RAP) content, were compacted and aged in a conventional oven at 85°C for zero (unaged), five, or 10 days. Asphalt binders were extracted and recovered from each aging level for chemical and rheological characterization. Seven blends of virgin asphalt binder and RAP binder were constituted to be similar to those used in the seven plant-produced asphalt mixtures. Subsequently, each asphalt binder blend was aged by rolling thin film oven (RTFO) and pressure aging vessel (PAV) for chemical and rheological characterization. Chemical and rheological characterization included Fourier transform infrared spectroscopy, high and intermediate temperature performance grade (PG), frequency sweep, and linear amplitude sweep (LAS) tests. Asphalt mixtures aged for five and 10 days resulted in asphalt binders that were less aged than similar ones aged by PAV when measured by LAS fatigue parameter ALAS, frequency sweep Glover Rowe (G-R) parameter, and intermediate temperature PG. However, unaged asphalt mixtures yielded asphalt binders with similar properties to those aged in RTFO as measured by high temperature PG. Correlation analysis between asphalt binder and asphalt mixture aging revealed that the G-R parameter has the highest coefficient of correlation among parameters. Further, new aging indices were introduced to capture the effect of polymer modification on aging susceptibility.

Viennese Ageing Procedure (VAPro): adaptions and further development to address low-temperature performance of aged asphalt mixtures

As for all organic material, bitumen is prone to ageing under atmospheric conditions. This ageing process changes the properties of materials as it becomes stiffer and more brittle over time. This leads to a deterioration of low-temperature and fatigue performance and limits the life span of road pavements. On asphalt mix scale, various ageing methods have been developed in the past decades. A lately developed method, Viennese Ageing Procedure (VAPro), conditions specimens using a gas mixture containing traces of reactive oxygen species (ROS). This paper presents improvements of the initial device and the development of a new cell for ageing prismatic specimens for low-temperature testing. Cooling tests were conducted to the show proof of principle of the new ageing cell in comparison to field-aged samples. With the VAPro method at hand, asphalt mixtures can be optimised in terms of their long-term performance including relevant impacts of ageing on the performance.

Aging Resistances Evaluation of Multi-dimensional Nanomaterials Modified Asphalt by Characterizing Binders Recovered from Aged Asphalt Mixtures

Abstract In terms of the aging susceptibility of asphalt, the multi-dimensional nanomaterials (MDNMs) have been developed to improve the aging resistance of asphalt. In comparison with most of previous studies that are only based on asphalt binder aging simulation methods to evaluate anti-aging properties of MDNMs modified asphalt, aging resistances of MDNM-modified asphalt were evaluated in this research by extracting and recovering binders from their aged asphalt mixtures and then characterizing the aging degree of the extracted binders in terms of physical, rheological, and chemical properties. Organic expanded vermiculite (OEVMT) and nanoparticles (nano zinc oxide [ZnO], nano titanium dioxide [TiO2], and nano silica [SiO2]) were chosen to compose three kinds of MDNMs. And six types of aging patterns (including mixing aging [MA], short-term aging [STA], compacted and loose long-term aging [CLTA and LLTA], and compacted and loose ultraviolet (UV) aging [CUVA and LUVA]) for asphalt mixtures were conducted. The results indicate that the ranking of aging degree for the six types of aging patterns is LUVA > LLTA > CUVA > CLTA > STA > MA. Regardless of the types of asphalt mixture aging patterns, the aging resistances of extracted MDNM-modified asphalt binders are all better than extracted pure asphalt binder, and the composite form of OEVMT combined with ZnO presents more significant improvements on asphalt aging resistance than the other two composite forms (OEVMT + SiO2 and OEVMT + TiO2).

Advances in Aging and Anti-Aging Research on Rubber-Modified Asphalt and Asphalt Mixtures

Waste rubber-modified asphalt has good anti-aging properties and can significantly improve the service life of asphalt pavements. For domestic and foreign scholars of rubber modified asphalt thermal oxygen aging, photo-oxidative aging and water aging some behavioural research, and rubber asphalt aging after the characteristics of the research progress are reviewed. Especially rubber-modified asphalt after light, water and other multi-factor agingsituations, the aging situation is more serious, for rubber-modified asphalt mixture aging, rubber asphalt anti-aging process research and analysis means are still very few, the future research must have more thinking.

Physicochemical characterization of short and long-term aged asphalt mixtures for low-temperature performance

Current pavement engineering shift towards Balanced Mix Design warrants performance testing of asphalt mixtures at low temperatures. The Bending Beam Rheometer (BBR) is an effective tool to characterize asphalt mixture’s low-temperature properties based on AASHTO TP125. This study utilized the BBR for physical characterization of 32 different asphalt mixtures composed of a PG 64–28 binder, two Job-Mix Formulae (JMF), four different RAP contents, and four different aging methods. Chemically extracted binder from the aged mixtures was then analyzed using the absorbance-based Fourier-Transform Infrared Spectroscopy (FT-IR) to identify the critical functional groups. The FT-IR analysis's semi-quantitative results were validated using the Energy Dispersive X-Ray Analyzer on the Scanning Electron Microscope (SEM-EDX). The reduction of carbon and sulfur concentration due to oxidation was correlated to the loss of cohesion between asphalt mastic and aggregates. Furthermore, microstructural damage was found in the aged specimens at a 200x magnification. Overall, this study provides a comprehensive and feasible method to perform physicochemical characterization of asphalt mixtures.

Effects of Microwave Heating and Long-Term Aging on the Rheological and Chemical Properties of Recovered Bitumen.

Microwave heating of asphalt pavement is a promising technique to reduce the maintenance and increase the service life of materials through self-healing of cracks. Previous studies have shown that microwave heating technology at high temperatures could damage the bitumen of asphalt mixture, which is an unwanted effect of the crack-healing technique. In this study, the effects of microwave heating and long-term aging on the rheological and chemical properties of recovered bitumen were quantified using a frequency sweep test and Fourier Transform Infrared Spectrometry analysis, respectively. The main results indicate that microwave heating has no significant effect on the aging performance of G* and for aged asphalt mixtures. However, for newer bitumens, the rheological properties G* and show minor changes after microwave heating was applied. Overall, this study confirms that microwave heating is a potential alternative for maintenance of asphalt pavements, without severely affecting the rheological and chemical properties of bitumen.

Determination of asphalt aging degree: a novel method to determine asphaltene content by centrifugal separation and air stripping technologies

The change of chemical composition of aged asphalt mixture is significant to determine the mechanism of asphalt aging and obtain the direction to produce an advisable asphalt rejuvenator for the specified aged asphalt. For this purpose, this article aims to determine the change of asphaltene after the asphalt aging by centrifugal separation combined with an air stripping method. The result indicates that the content of asphaltene in aged asphalt is approximately 25%, while the content of asphaltene in base asphaltene is about 20%. In addition, compared with traditional distillation-extraction method, the new approach has the advantages of simplicity, rapidity, accuracy and a reduction in pollution to the environment. Furthermore, the analytical result could be provided for preparation and application of asphalt rejuvenators.

Effect of palm oil capsules on the self-healing properties of aged and unaged asphalt mixtures gained by resting period and microwave heating

Palm oil was used as a new rejuvenating agent for manufacturing calcium alginate capsules to study the self-healing properties of aged and unaged asphalt mixtures. To optimize the palm oil capsule for use in the asphalt mixture, nine types of calcium alginate capsules with various oil-to-water (O/W = 5, 10, and 15 %w) and calcium chloride-to-water percentages (CaCl2/W = 2, 4, and 6 %w) were prepared, and compressive strength, thermal sensitivity, size measurement, density measurement, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) tests were performed on them. Asphalt mixtures with various percentages of optimum capsules (0, 0.35, and 0.7% by total weight of the mixture) were prepared in unaged and long-term-aged conditions, and the effect of capsules on the stiffness modulus of aged and unaged asphalt mixtures was investigated by the indirect tensile stiffness modulus (ITSM) test. Via the semicircular bending (SCB) test, self-healing with a resting period and microwave healing were used to investigate the self-healing properties of aged and unaged asphalt mixtures with and without capsules. To reduce heating time and energy consumption, the effect of incorporating steel wool fibers (SWF) on the microwave heating of palm oil capsule-containing asphalt mixtures was investigated. The results showed that the use of palm oil capsules significantly increased the self-healing capability of the aged and unaged asphalt mixtures. The microwave healing method promoted the healing speed and healing level of the capsule-containing aged and unaged asphalt mixtures. Moreover, with the use of SWF in microwave healing, a healing level similar to that of SWF-less asphalt specimens was obtained in a shorter heating time.

Multilevel Analysis of the Aging Mechanisms and Performance Evolution of Rubber-Modified Asphalt

Rubber powder is widely used to modify base asphalt binder to improve the low-temperature performance and crack resistance of asphalt mixtures. This paper investigates the aging mechanism and performance evolution of rubber-modified asphalt in terms of three levels: rubber powder, rubber-modified asphalt, and rubber-modified asphalt mixture. The multilevel analysis results show that mass loss, phase transition, and melting occur during the process of rubber powder aging, and scanning electron microscope images indicate that the surface morphology of the rubber powder becomes smoother. The aging of base asphalt leads to the volatilization and oxidation of light components, resulting in the production of carbonyl and sulfoxide groups and a reduction in the swelling between the rubber powder and aged base asphalt. The aging of rubber powder leads directly to a significant decrease in the modification effect of the rubber; thus, rubber powder aging plays a more decisive role in the degradation of rubber-modified asphalt than base asphalt aging. By contrast, the performance indicators of aged rubber-modified asphalt are able to reach their highest values due to the effective blending between the rubber powder and base asphalt, which results in an enhanced antiaging capability. The sensitivity of all performance indicators of rubber-modified asphalt to the aging temperature is relatively low, except for the 5°C ductility index. Therefore, the mixing temperature needs to be strictly controlled to a specified value when rubber-modified asphalt is applied in cold areas that require low-temperature stability of the mixture. As for the aged rubber-modified asphalt mixture, the dynamic stability improved significantly, the ultimate tensile strain at low temperature decreased, and the antifatigue performance decreased to different extents under different stress ratios.

Experimental assessment and modeling of fracture and fatigue resistance of aged stone matrix asphalt (SMA) mixtures containing RAP materials and warm-mix additive using ANFIS method

Experimental assessment and modeling of fracture and fatigue resistance of aged stone matrix asphalt (SMA) mixtures containing RAP materials and warm-mix additive using ANFIS method

Accelerated aging of loose asphalt mixtures using ozone and other reactive oxygen species

Efficient and practical techniques to simulate aging of asphalt mixtures is a focus area for practitioners around the world. In this study, a laboratory procedure was developed for accelerated aging of loose asphalt specimens using highly oxidative gas consisting of two types of reactive oxygen species (ROS) i.e., ozone (O3) and nitrogen oxides (NOx). The procedure involved the aging of loose mixtures in an enclosed ROS rich environment for a period of 1 day at 95 °C. The chemical and rheological properties of the extracted binders from 5 different mixtures aged using this method were then compared to analogous binders aged using a benchmark of loose mixture aging at 95 °C for 5 days in a laboratory oven. Different metrics for oxidation and aging were comprehensively evaluated including extent of oxidative groups by Fourier transform infrared spectroscopy (FTIR), high and low temperature rheological properties using dynamic shear rheometer (DSR), and polarity based chemical fractionation into saturates, aromatics, resin and asphaltene (SARA) fractions. Favorable chemo-mechanical correlations were obtained from the results which confirmed that the mixtures aged using the ROS aging method showed similar or higher levels of aging just after 24 hrs when compared to the conventional 5-day aging method. Overall, the procedure developed serves as a proof of concept and provides encouraging results for further work towards the development and standardization of such an approach.

A laboratory investigation on thermal properties of virgin and aged asphalt mixture

In this paper, the thermal properties of three dense graded asphalt mixtures, 20 mm DBM, AC 14, and AC 6, are presented. Density and air voids of the compacted specimens are also shown. Thermal conductivity was measured in the laboratory for non-aged, short-term aged and long-term aged asphalt mixtures at three different temperatures 19 (±1) oC, 65 (±5) oC, and 80 (±5) oC. Specific heat capacity and thermal diffusivity were calculated from equations derived from the literature. Heat penetration depth was also calculated and shows the heat from the thermal conductivity instrument heat source that dissipates into the asphalt specimens. The results were analysed to determine the effect of air voids content, transient line source (TLS) method, temperature and aggregate size in thermal conductivity and the effect of aging on the thermal properties of the asphalt mixtures studied. It was concluded that there is a minimal effect in thermal conductivity for 4% to 6.5% air voids. The method of measurement and temperature affect considerably thermal conductivity. However, the results were inconclusive in the effect of aggregate size on thermal conductivity. The effect of asphalt aging in thermal conductivity and thermal diffusivity varied between the asphalt mixtures studied and was relative to the temperature. Asphalt aging did not affect specific heat capacity.

Novel Model to Predict Critical Strain Energy Release Rate in Semi-Circular Bend Test as Fracture Parameter for Asphalt Mixtures Using an Artificial Neural Network Approach

Growing use of recycled asphalt materials in asphalt pavement means the current volumetric-based Superpave mixture design may not address durability concerns arising from replacement of a proportion of virgin binder with recycled ones. To address this limitation, performance-based testing is introduced to supplement conventional volumetric mixture design in assessing cracking performance of asphalt mixtures. Louisiana Department of Transportation and Development’s Specifications for Roads and Bridges specify a criterion for the critical strain energy release rate, Jc, obtained from semi-circular bend (SCB) test as a complement of current practice to evaluate cracking resistance of asphalt mixtures. Quality control/assurance practices, however, require SCB samples to be long-term aged for five days at 85°C, which is a time-consuming process. Therefore, it is beneficial to be able to estimate SCB Jc for long-term aged asphalt mixtures based on SCB Jc measured from plant-produced asphalt mixtures. Asphalt mixture aging is complex, and various variables are involved in the aging process, including volumetric properties of asphalt mixture and chemical/rheological characteristics of asphalt binder. With the capability of artificial neural network (ANN) to address complex relationships between input and output variables, this study aims to predict the fracture parameter, SCB Jc, of asphalt mixtures using ANN. A total of 34 asphalt mixtures were selected for this study. SCB fracture test and asphalt binder tests for chemical and rheological characterization were conducted. Stepwise regression analysis was used to determine the significant parameters in the correlation with SCB Jc. With determined significant parameters, ANN using the gradient descent backpropagation approach was then applied to develop and validate the predictive model. It was shown that the developed ANN model was able to predict the fracture parameter, SCB Jc, of asphalt mixtures more accurately than linear and non-linear regression models.

Studying the Early Cracking Behavior of Asphalt Concrete Base Course

In Iraq, there are some asphalt concrete mixtures suffer from appearing of cracking and deformation immediately after finishing the construction of a base course. In the flexible pavement, the pavement is considered to be degraded after opening to traffic by repeated traffic loading, climatic conditions, aging of asphalt mixture, etc. Crack plays a critical mode in pavement degradation. Several experimental studies have been carried out to gain a deeper understanding of the environment and weak construction monitor the action of pavement fractures. However, one downside of these previous studies was that the majority of them were carried out in a laboratory environment. A trial road section was studied after finishing base course construction by monitoring the early cracking. The major causes of appearing the early cracking have been investigated and debated. In this survey, three trial road sections with defined asphalt layers were considered. These trial sections were constructed with local materials brought from Nasrya refinery and Najaf quarry. On the basis of the findings obtained, two sections have deteriorated, while the third one was made as control for comparison purposes The observed early cracking could be attributed to the asphalt cement type and poor construction procedure occurring in an asphalt base layer as a result of low underlying sub-base course type and specifications.

Durability and Aging Characteristics of Sustainable Paving Mixture

With the industrial revolution, many inventions have been introduced with many solid waste materials in returns. This study investigates the potential recycling of waste plastic sheets, made from low-density polyethylene, as asphalt modifier in the paving mixture. The shredded plastic sheet was used in the asphalt mixture via the wet process. The dosage rate was set up to 9 % by weight of asphalt binder (0, 3, 6, and 9)%. The experimental program was designed to assess the mechanical properties (Marshall stability and flow, and volumetric properties), durability, and short-term aging of asphalt mixtures, in addition to economical assessment. The test results revealed the applicability of using this solid waste material in paving construction as a surface layer, since its usage enhances the pavement performance by increasing stability, index of retained strength, and volumetric characteristics before and after aging as well as saving in cost. The best enhancement can be achieved with 6% of recycled low-density polyethylene.

Evaluation of the Long-Term Performances of SMA-13 Containing Different Fibers

To clarify the influence of fiber type on the long-term performance of stone mastic asphalt (SMA), this paper used basalt fiber (BF) and lignin fiber (LF) to modify SMA-13 (SMA with aggregate nominal maximum particle size of 13.2 mm) asphalt mixture. The pavement performances (high-temperature performance, cracking resistance at low and medium temperature, and water stability) of the two kinds of fiber-reinforced SMA-13 were checked under different aging degrees (unaged, short-term aged and long-term aged), scanning electron microscope (SEM) test was conducted to explain the strengthening mechanism of the fibers. Fourier transform infrared spectrometry (FTIR) was used to analyze the changes in the chemical composition of asphalt after aging. The results of the wheel tracking test and uniaxial penetration test showed that the high-temperature performance of the BFSMA-13 (defined as the SMA-13 containing BF) is better than that of the LFSMA-13 (defined as the SMA-13 containing LF) at different aging degrees. The high-temperature performance of BFSMA-13 increases with the increase of the aging degree, while the aging process decreases the high-temperature property of LFSMA-13. The results of the three-point bending test and semi-circular bending (SCB) proved that BFSMA-13 is more capable of deformation and less prone to cracking at low and medium temperatures. The results of the immersion Marshal test indicated that BF can better improve the strength and the water stability of the SMA-13 mixture than LF. The SEM images showed that basalt fibers form a solid three-dimensional network structure in the mixture which could contribute to the strengthening of the mixture. The results of infrared spectroscopy analysis showed that styrene–butadiene–styrene (SBS) degrades during asphalt mixture aging, and that the chemical composition of asphalt changes more after aging in LFSMA-13 than in BFSMA-13. The conclusions of this study help toward further understanding of the performance changes of the SMA-13 mixture during its service life and to guide the selection of fiber additives for SMA-13 mixtures.