Aged Asphalt Binders Research Articles

Influence of Ultraviolet Irradiation Quantity on Asphalt Rheological Performance

The DSR was conducted to evaluate the influence of ultraviolet aging on asphalt rheological performance. In the experiment, RTFOT test was used to simulate the short-term aging of asphalt binder, indoor intelligent ultraviolet aging box is used to simulate ultraviolet aging of asphalt. The aging temperature was set at 50 ��C. Aging days were 2 days, 4 days, and 6 days. For high temperature frequency scanning and low temperature frequency scanning of ultraviolet aging asphalt. The experimental results show that the ultraviolet aging have great influence on asphalt basic performance indicators and rheological properties.

Effect of Waste Edible Vegetable Oil on High Temperature Properties of Different Aged Asphalts

Based on the asphalt rejuvenation theory and some related studies, waste cooking oil can be used for asphalt regeneration. The objective of this study is to investigate the high temperature properties of aged asphalt binder with waste edible vegetable oil. The materials used for this study included three sources of virgin asphalt (60-80 grad, 40-60 grad, SBS modified asphalt), three sources of aged asphalt (virgin asphalt aged by RTFOT and PAV), and waste edible vegetable oil with five percentages (3.0, 4.0, 5.0, 6.0, and 7.0% of rejuvenating asphalt). The high temperature characteristics of these rejuvenated asphalts were tested including viscosity and rutting resistance factor (phase angle and complex modulus). The results indicated that three aged asphalt with an appropriate amount of waste edible vegetable oil can respectively achieve the demand of virgin asphalt in rutting resistance factor, phase angle and complex modulus. It means that waste edible vegetable oil could recover high temperature performance of aged asphalt to the level of original asphalt at a certain amount. Moreover, waste edible vegetable oil can slightly reduce the viscosity value of the aged asphalt and thus decrease the mixing and compaction temperature of the mixture.

Turning Back Time

Countermeasures to the aging of bituminous asphalt binders is a highly important topic for service-life extension of asphalt in the field and for recycling old pavements into new structures with similar functional requirements as the original structure. Countermeasures are usually achieved by applying additives that restore the adhesive and mechanical properties of the original bituminous binder. The additives are commonly termed (asphalt) rejuvenators. This study examined the performance of two very distinct rejuvenating agents. The effectiveness of rejuvenators is usually measured by comparing the penetration and softening point of the rejuvenator-aged bitumen blend with reference values of the virgin binder. The study used a dynamic shear rheometer to evaluate the rejuvenating capabilities of the two additives. The microstructures of the virgin binder and the rejuvenated blends were obtained by atomic force microscopy. Subsequently, the rheological results were related to the microstructure morphologies. From the rheological experiments, both rejuvenators exhibited the desired softening and property-restoring performance. However, there was a strong difference in the amount of rejuvenator needed to achieve complete rejuvenation. By correlating rheology to the microstructural observations, the effects of the rejuvenators were found to be distinct at microscopic length scales: rejuvenation was achieved by distinct chemophysical mechanisms. One of the rejuvenators restored the virgin microstructure, whereas the other rejuvenator generated a new morphology. Thus, the study demonstrated that by combining rheological and microstructural techniques, the mechanism and performance of rejuvenation can be understood. This finding may help guide future designs and optimization of asphalt-rejuvenating agents.

Characterization of Reclaimed Asphalt Pavement (RAP) for Use in Bituminous Road Construction

A good road network is a critical infrastructure requirement for rapid economic growth. It provides connectivity to remote areas; provides accessibility to markets, schools, and hospitals; and opens up backward regions to trade and investment. Roads play an important role in inter-modal transport development, through links with airports, railway stations, and ports. Road network in India aggregates to about 4.2 million kilometers. This extensive road network, the second largest in the world only after US, caters to about 65 per cent of the freight traffic and 87 per cent of the passenger traffic. National Highways (NH) constitute about 70,934 kilometers which is only 2 percent of the total network. However, it caters to nearly 40% of the total road traffic. State Highways (SH) and Major District Roads (MDR) together constitute the secondary system of road transportation which contributes significantly to the development of the rural economy and industrial growth of the country. The conventional method of providing bituminous surfacing on flexible pavements require significant amount of energy for production of bituminous binder from crude petroleum, drying aggregates and subsequently production of bituminous mix at hot mix plant (HMP).Hot mix recycling is the process in which reclaimed asphalt pavement materials are combined with new materials, sometimes along with a recycling agent, to produce hot mix asphalt mixtures. When properly designed, recycled mixtures can have better or similar performance to those of new conventional hot mix asphalt mixtures.Recycling or Rejuvenating agents have been defined as organic materials with chemical and physical characteristics selected to restore properties of aged asphalt to desired specifications. In selecting the recycling agent, the viscosity characteristics of the combined aged asphalt binder and the recycling agent are the determining factors. These agents are also known as softening agents, reclaiming agents, modifiers, fluxing oils, extender oils, and aromatic oils. The choice of Recycling Agent (RA) grade will depend on the amount and hardness of the asphalt in the aged pavement. In general, the lower viscosity RA types can be used to restore aged asphalts of high viscosity and vice versa. Laboratory studies have been carried out on asphalt mixes with RAP material and rejuvenating agent and their performance has been compared with virgin asphalt mixes. Various performance tests such as Retained Stability, Indirect Tensile Strength (ITS), Creep test, beam fatigue test, resilient modulus and wheel tracking test has been carried out to compare the performance properties. This paper presents the results of all such performance tests carried out on asphalt mixes with RAP and virgin mixes. The laboratory results indicate that the asphalt mixes with RAP and rejuvenating agent provide better performance compared to virgin mixes. The paper also recommends that the Accelerated Pavement Testing Facility (APTF) should be put to use to evaluate the actual field performance of recycled pavements in a faster and effective manner.

The Applicability of Estimated Equations of Recycling Agents on the Viscosity Variety of Aged Asphalt Binders

This study was to perform the viscosity test of adding different ratios (from 10% to 40%) of three recycling agents (RAs), namely RA25, RA75 and RA250, to the reclaimed asphalt binder (RAB) containing a viscosity of 42800 poises. The purpose of the study was to determine the effects of various RAs on the viscosity of aged asphalt binders. The viscosity values were also estimated based on the recycling model of aged asphalt binder developed by authors and the equations developed by Arrhenius (1887), Grunberg and Nissan (1949) and Epps et al. (1980). The results show that there are significant variations in the viscosity of recycling asphalt binder when being added different ratios of RA. The estimated viscosity values computed by the recycling model of aged asphalt binder are closer to the tested results when compared with the equations developed by Arrhenius (1887), Grunberg and Nissan (1949) and Epps et al. (1980). Furthermore, the Recycling Index (RI) developed by the recycling model of aged asphalt binder can clearly and precisely reveal the recycling performance of different kinds of RAs. The Gmix from the equation developed by Grunberg and Nissan (1949) has an apparent effect on estimating the viscosity when adding RA to the RAB.

Effect of long-term ageing on RAP mixtures: laboratory evaluation of plant-produced mixtures

As the use of reclaimed asphalt pavement (RAP) in asphalt concrete mixtures increases, it is important to understand how the addition of already aged asphalt binders affects the overall properties and performance of the mixture. In this study, four plant-produced mixtures containing 0%, 20%, 30%, and 40% RAP were long-term oven aged in the laboratory to three levels. Mixture testing included uniaxial complex modulus and fatigue. Recovered binder testing included performance grading (PG) and rheological characterisation. The mixture testing showed that the RAP mixtures stiffen due to laboratory ageing at a slower rate than virgin mixtures and that the impact of the presence of RAP on material properties decreases with ageing time. The relative fatigue performance of the mixtures changes dramatically in stress versus strain control, indicating the importance of linking mixture and pavement design. The recovered binder properties show increase in the high continuous PG, minimal impact at the intermediate continuous PG and a slight increase in the low continuous PG with ageing time. The complex shear modulus shows an increase in stiffness and a decrease in phase angle with ageing. The binder and mixture properties generally show the same qualitative trends with respect to RAP content and ageing level; quantitative comparisons of several parameters show some correlation, indicating that binder properties may be used to evaluate the expected mixture properties measured in the lab.

The effects of environmental aging on Colombian asphalts

Environmental exposure affects asphalt mixture performance. Using a Dynamic Shear Rheometer (DSR), we determined there was a correlation between the environmental aging of Colombian asphalt binders AC-20 and AC-30 and changes in their rheological properties. We aged asphalts using the Rolling Thin Film Oven (RTFO) test and the Pressure Aging Vessel (PAV), as well as an ultraviolet (UV) chamber designed especially for this project. This aging chamber generates UV radiation with radiation-condensation periods up to 500h. Physical properties were evaluated by penetration, ductility and softening point tests. Chemical evaluation was made through Fourier Transform Infra-Red (FTIR) Spectroscopy as a complement to Corbett SARA fractions. We then compared the physical, chemical and rheological aspects of the original and aged asphalt binders. On one hand, short-term aged asphalt binders showed a recuperation in ductility and |G∗| due to an increase in resin fractions. On the other hand, long-term aging produced by the PAV was similar to that of the RTFO treatment with an additional 500h of UV radiation. We carried out the dynamic evaluation of asphalts with Multiple Stress Creep Recovery (MSCR) tests. Taken together, these results show that AC-20 and AC-30 age differently based on their respective SARA fractions content: AC-30 displays higher levels of strain than AC-20 because of its increased levels of solid fractions. We found that RTFO treatment produced similar results in the asphalt binders after 100h of UV radiation. Additionally, chemical testing demonstrates that during short-term aging, saturates and naphthene aromatics convert into resins—the result of oxidation—until productions of these resins stops. Then, during the long-term resins are converted into asphaltenes.

Investigation of Delamination on I-65 in Indiana

Abstract This paper presents an investigation of delamination on the northbound driving lane of I-65 near Brookston, IN, utilizing field pull-off tests to evaluate interface bonding strength. In addition, ultrasonic test, asphalt binder test, and mix property (mechanical and volumetric) tests [i.e., dynamic shear rheometer (DSR) test, asphalt binder extraction, binder content, sieve analysis, and mix specific gravities] were conducted to explore the cause(s) of delamination. The pull-off test results showed that the delaminated pavement had a weaker interface bond, which generated more top-down fatigue cracking. In addition, the delaminated pavement contained more aged asphalt binder and a higher percentage of air voids, which could have accelerated top-down fatigue cracking as well. In conclusion, the causes of delamination were a combination of weak interface bonding and asphalt mix durability of the surface course.

Characterizing Rheological Properties of Binder and Blending Efficiency of Asphalt Paving Mixtures Containing RAS through GPC

AbstractUse of recycled asphalt shingles (RAS) into asphalt mixture has become more popular in asphalt paving industry due to dwindling natural resources and potential economic benefits. However, one critical question arises as to how much of aged asphalt binder in RAS can be effectively blended with virgin binder during mixing and construction. This paper presents a laboratory study in which gel permeation chromatography (GPC) was used to determine the blending efficiency of RAS. A correlation was first established between percentages of large molecules (LMS) obtained from GPC and rheological properties of RAS binders. Then the relationship was used to estimate the blending efficiency of RAS binders. The effects of aggregate size, RAS content, and mixing time on blending efficiency were evaluated. The test results show that the percentage of LMS was highly correlated with the complex shear modulus (G*) of asphalt binder. Increasing mixing time led to a better blending of RAS mixture. Aggregate size did n...

Comparison of Laboratory and Field Aging Properties of Different Asphalt Binders

Abstract In the past four decades, many states in the United States, including Arizona, have successfully used modified binders such as asphalt rubber (AR), defined by ASTM D6114, to reduce pavement distress and associated maintenance costs. The main objective of this study was to understand the aging characteristics of unaged and aged neat asphalt and AR binders using more than 25 years' worth of data from field and laboratory studies covering over 157 test sections in Arizona and 318 binder types with 957 data points. Trend relationships of the routine binder test results for neat and AR binders with respect to age were developed and resulted in fair correlations. AR binders had higher core-aged penetration and very low viscosities at all time-scales relative to neat binders. Furthermore, the performance grade system's shear modulus G*–phase angle δ relationship for the neat binders was excellent and rational with respect to aging. G* and δ for the neat binders were mathematically related to the routine microviscosity test. The inverse relationship of age versus microviscosity relative to δ exemplified that with an increase in the binder (micro)viscosity, the material showed increased elastic behavior. In a well-connected analysis using special sections of neat and AR binders, (i) neat binder data were positioned in close proximity to the δ–age relationship within the pressure aging vessel (PAV) long-term aging zone, validating that the PAV method ostensibly used for neat binders is rational and represents 8 to 10 years of aging and 15 % cracking; and (ii) AR binder data were not near the laboratory δ–age relationship, indicative of the fact that the viscous component (δ) symbolizing the aging phenomenon altered at a slower rate for AR than for the neat binders. Although the overall findings represent limited AR data, this study has provided a fair understanding of the aging characteristics of the two different binders.

Special Issue on Materials Innovations for Sustainable Infrastructure

DOI: 10.1061/(ASCE)MT.1943-5533.0000840Nowadays, the concept of sustainability has gained widespreadacceptanceandawarenessinthetransportationinfrastructureindus-try (Huang and Liu 2011; Mehta 2009). Numerous innovations inpaving materials and construction techniques have been adopted tomeet the challenge of sustainable development (Huang et al. 2012;Miller and Bahia 2009; Aitcin 2007; Van Dam et al. 2011).This special issue contains 16 technical papers in this area, whichcan be divided into the following four categories: (1) recycledmaterials, (2) sustainable materials accommodating climaticchange, (3) pavements for longer service life, and (4) low-energy-consumption materials.Recycled MaterialsRecycling of solid waste materials into paving materials reducesnot only environmental issues associated with waste disposal butalso the demand for virgin asphalt cement or Portland cementbinder, and coarse and fine aggregates, leading to potential costsavings. This is especially important when faced with the ever-growing world population and increasingly dwindling naturalresources. Recycled asphalt pavement (RAP), recycled asphaltshingles (RAS), crumb rubber, and steel slag have been widelyaccepted by state highway agencies and recycled into asphalt pave-ments (Schroeder 1994; Shelburne and DeGroot 1998; Huanget al. 2002, 2005a, 2007, 2010a, b, 2011; Xiao et al. 2007, 2009;Shu et al. 2008, 2012; Zhao et al. 2012, 2013). In addition to thefour types of supplementary cementitious materials (SCMs)—flyash,slag,silicafume,andnaturalpozzolans—manyothermaterialssuch as recycled concrete aggregate (RCA), cement kiln dust(CKD), foundry sand, waste glass, bottom ash, crumb rubber,plastics, ceramics, and even RAP have been recycled into Portlandcement concrete (PCC) materials (Ansari et al. 2000; Naik 2002;Huang et al. 2004, 2005b, 2006b, 2009b, 2013; Li et al.2004a, b). Like SCMs contributing to the properties of hardenedPCC through hydraulic and/or pozzolanic reactions, RAP andRAS can also improve the binding properties of asphalt pavingmaterials through the aged asphalt binder in them, which makesthem more technically and economically beneficial.Thisspecialissuepresentssixtechnicalpapersregardingtheuseof recycled materials such as RAP, RCA, waste phosphorous slag,sludge, low-quality fly ash, and waste ceramic aggregate. Lin et al.investigated the effects of rejuvenator sealer material on aged as-phalt binder through laboratory testing. Their test results show thatrejuvenator can serve as a softening agent, reducing viscosity andcomplex modulus of aged asphalt binder. Chemical analysis indi-cates that addition of rejuvenator can slightly change the fractionsof aged asphalt binder and thus balance its asphaltene-malteneratio. Because rejuvenator is not very common in the recyclingof RAP in asphalt mixtures, this study may shed new light on com-bining rejuvenator with RAP and serve as a booster to incorporatemore RAP in asphalt paving materials.Self-healing is an intrinsic property of asphalt binder and maypotentially be beneficial in improving the properties of recycledasphalt mixtures. Qiu et al. developed three new test methods tosimulatetheself-healingprocessofasphaltbinder,mastic,andmix-ture in the laboratory and investigate the self-heading mechanism.Intheirstudy,theself-healingprocesswastobehypothesizedtothereverse process of cracking, consisting of two phases—crackclosure and strength gain. They also found that the self-healingcapability of asphalt materials is significantly affected by twofactors—temperature and healing time.Qian et al. and Feng et al. both used waste industrial by-productin asphalt mixtures. Qian et al. incorporated phosphorus slag asmineral filler in hot-mix asphalt (HMA) and used multiple charac-terization techniques to assess the feasibility of recycling thisindustrial waste into HMA mixtures. Their test results indicate thatphosphorus slag filler significantly increases the resistance ofHMAs to rutting and moisture damage. Feng et al. attempted torecycle ceramic waste aggregate (CWA) into wearing layer of as-phalt pavement. Their concern is on the thermal effect and the mix-ture performance attributed to adding CWA. Their finite elementmethod (FEM) simulation results show that CWA can reducethe thermal conductivity of asphalt mixtures and subsequently re-duce the temperature gradient of pavement. Basing on the perfor-mance test results, they recommended that less than 40% CWA beadded into asphalt mixtures to replace natural coarse aggregates.Qiao and Chen introduced an innovative chemical admixturecalled mesoporous inorganic polymer (MIP) to improve themechanical properties and early-age shrinkage resistance of re-cycled aggregate concrete (RAC). The properties of RAC are usu-ally compromised because of the addition of RCA, such asincreased shrinkage and creep, reduced strength and modulus,and poor durability. To overcome these inferior properties, a prom-ising chemical admixture, an atomic polymer technology (APT) inthe form of MIP, was added and successfully enhanced themechanical and early-age shrinkage performance of RAC. Com-bined with this technology, more RAC can potentially be madeto promote sustainability in the PCC industry.Yang et al. used river sludge, low-quality fly ash, and glasspowder to produce high-strength ceramsite. They looked into dif-ferent recipes and different fabrication conditions and successfullyproducedhigh-strengthceramsitethatmeetsChinastandards.Their

Weathering aging of modified asphalt binders

The effect of solar radiation on aging of the asphalt binder can be considered relevant due to the high level of insulation in several countries including Brazil. This work aims to study the weathering aging of conventional asphalt binder and styrene–butadiene–styrene (SBS), hydrated lime, reactive ethylene terpolymer (RET) and polyphosphoric acid (PPA) modified asphalt binders. These modifiers represent the main compounds used to obtain improved performance from asphalt binder. The degradation of the samples was analyzed using Fourier transform infrared spectroscopy and thermal analysis. The styrene–butadiene–styrene, polyphosphoric acid, and hydrated lime asphalt binders showed a higher photo degradation resistance than the conventional asphalt binder for aging time up to 200h, considering the infrared spectroscopy results. The temperature of maximum degradation increased after aging for the SBS asphalt binders and for the hydrated lime asphalt binders.

Approach for Quantifying the Effect of Binder Oxidative Aging on the Viscoelastic Properties of Asphalt Mixtures

Because of the noted influence of oxidative aging on mixture properties and pavement performance, it is becoming imperative to have a more complete understanding of the influence of asphalt binder aging on the viscoelastic behavior of asphalt mixtures. This study proposes a new approach to correlating the oxidative aging of asphalt binder for carbonyl functional groups with the viscoelastic behavior of asphalt mixtures for a continuous relaxation spectrum. The asphalt mixture complex modulus and the carbonyl area for the recovered asphalt binder were measured for mixtures subjected to varying durations of long-term aging in the laboratory. The continuous relaxation spectrum was obtained analytically from the 2S2P1D model of complex modulus of asphalt mixture through the inverse Fourier–Laplace transform approach. A consistent horizontal shift in the continuous relaxation spectrum was observed for all mixtures with the increase in aging duration. However, the shape and the amount of shifting of the spectra were mixture dependent. In particular, mixtures with higher asphalt binder absorption exhibited the greatest shift in the continuous spectra for both unmodified and polymer-modified asphalt mixtures. Good correlations were observed between the carbonyl in asphalt binder and the continuous relaxation spectrum parameters of the asphalt mixture. Such relationships should permit the incorporation of long-term oxidative aging directly into the constitutive equation used in pavement response analyses.

Influence of Hydrogreen Bioasphalt on Viscoelastic Properties of Reclaimed Asphalt Mixtures

The incorporation of reclaimed asphalt pavement (RAP) into asphalt mixtures exposes some challenges from the design perspective because of the aged asphalt binder in RAP. Steps are being taken to offset the addition of stiff materials, often with the use of rejuvenating additives. This paper summarizes the laboratory evaluation of one of the available bio-rejuvenating agents called BituTech RAP. High RAP content mixtures used in Manitoba, Canada, were evaluated to study the impact of BituTech RAP on the viscoelastic properties of asphalt mixtures to overcome any possible moisture damage or thermal cracking problems that might arise in such a wet–freeze environment. The laboratory experiment consisted of the production and test of mixtures that contained 15% and 50% RAP, with and without BituTech RAP. The 2S2P1D analogical model was used to generate the complex modulus (E*) of the various evaluated mixtures and to assess the influence of BituTech RAP on the storage and loss moduli. The addition of BituTech RAP improved the moisture resistance of the mixtures that contained RAP, as observed after three freeze–thaw cycles. The addition of BituTech RAP restored the thermal cracking properties of the mixtures revealed by the thermal stress restrained specimen test. The use of BituTech RAP could result in cost savings without the need to use a softer binder, as long as the high-temperature properties of the mixtures were not jeopardized.

Effect of Rejuvenator Sealer Materials on the Properties of Aged Asphalt Binder

AbstractThe maintenance of asphalt pavement has become recognized as a critical issue in China. The objective of this study is to investigate the influence of using rejuvenator sealer materials on aged asphalt by means of laboratory analysis. First, asphalt binder first aged by rolling thin-film oven test and ultraviolet light. This aged asphalt was treated by two kinds of rejuvenator sealer materials. The performances of both aged binder and rejuvenator treated binder were evaluated by means of viscosity, temperature sweep, creep recovery, fatigue, and component analysis tests. The results indicated that both rejuvenator sealer materials can significantly decrease the viscosity and complex modulus of aged asphalt. Moreover, applying rejuvenator sealer materials can balance the asphaltene–maltene ratio of aged asphalt to some degree. Aged asphalt can be efficiently softened with the rejuvenator materials, which proves that rejuvenator sealer materials can be used for maintenance to improve the performance...

Retracted: Quantum-Chemistry–Based Study of Beech-Wood Lignin as an Antioxidant of Petroleum Asphalt

Oxidative hardening or aging of asphalt binder can lead to increase in viscosity, separation of components, loss of cohesion and adhesion, and eventually the degraded engineering performances. A common practice to minimize asphalt aging has been to use chemical additives or modifiers as antioxidants. The current state of knowledge in asphalt oxidation and antioxidant evaluation concentrates on monitoring the degradation in asphalt’s physical properties, mainly the viscosity and ductility. Such practices although satisfying direct engineering needs does not contribute to the fundamental understanding of the asphalt aging and antiaging mechanisms. As such, this study was initiated to study the antioxidation mechanisms of bio-based additives, using the beech-wood lignin as an example, by developing a quantum-chemistry based chemophysical environment in which the various chemical reactions among asphalt components, antioxidative ingredients and oxygen molecules, as well as the incurred physical changes can be studied. The techniques of X-ray photoelectron spectroscopy (XPS) were used to prove the validity of the modified and unmodified asphalt models.

Model developments of long-term aged asphalt binders

Artificial neural networks (ANNs) are useful in place of conventional physical models for analyzing complex relationship involving multiple variables and have been successfully used in civil engineering applications. The objective of this study was to develop a series of ANN models to simulate the long-term aging of three asphalt binders (PG 64-22, crumb rubberized asphalt modifier, PG 76-22) regarding seven aging variables such as aging temperature and duration, m-value, mass loss of pressurized aging vessel (PAV) samples, percentages of large and small molecular sizes of high pressure-gel permeation chromatographic (GPC) testing, and binder stiffness. The results indicated that ANN-based models are more effective than the regression models and can easily be implemented in a spreadsheet, thus making it easy to apply. The results also show that the aging temperature, aging duration, percentage of large and small molecular sizes, and binder stiffness are the most important factors in the developed ANN models for prediction of penetration index after a long-term aging process.

Laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures

The objective of this paper is to investigate the effects of rejuvenator seal materials (RSM) on performances of hot asphalt mixtures (HMA). Firstly, frequency sweep test is conducted to determine the rejuvenating effect of RSM on aged asphalt binders. Then, high temperature performances of RSM treated HMA are studied by means of wheel tracking test, static creep test and indirect tensile test. Lastly, raveling test and skidding resistance test of RSM treated HMA are also performed in this paper. The results indicate that RSM can effectively soften the aged asphalt binder, and the application of RSM may decrease the high-temperature performance of HMA. Moreover, RSM increase the raveling resistance and decrease the skidding resistance of HMA. The results of this paper help to have a better understanding on the effects of RSM on HMA.

Effects of Sasobit® content on the rheological characteristics of unaged and aged asphalt binders at high and intermediate temperatures

This paper describes the rheological properties of PG64, PG70, and PG76 asphalt binders blended with different Sasobit® contents. The rheological properties of the Sasobit®-modified binders were characterized after being subjected to different aging conditions using the dynamic shear rheometer (DSR) and rotational viscometer (RV) according to SuperpaveTM test protocols. The results indicated that the characterization of aging in terms of the Aging Index (AI) depends on the rheological property of the asphalt binder selected for use in evaluating aging, the amount of Sasobit®, the binder type, and the temperature range. Linear relationships between failure temperatures of unaged and short-term-aged asphalt were observed for three binder types. Design charts were developed to select the appropriate Sasobit® content as a function of temperature, taking into consideration the stiffening effects of Sasobit®, using the SuperpaveTM fatigue factor and asphalt mix construction temperatures.

Improvements on asphalt mixtures rutting performance characterization by the use of low shear viscosity

The relationship between the rutting performance of dense asphalt concretes and the low shear viscosity (LSV) of different asphalt binders was analysed in a previous work. A LSV limit was found for the original asphalt to prevent the rutting of the mixtures, and in addition, a model to predict the rutting performance based on the LSV of the asphalt binder was validated. With the aim of amplifying the criterion previously found, the performances of micro and stone mastic asphalt mixtures are studied in this work. Conventional, multigrade and polymer modified asphalts were used as binders. Considering that the properties of original and aged asphalts must be taken into account for a better asphalt binder characterization, LSV measurements on aged asphalts were also done in order to analyse their relationship to the mixtures rutting performance. The micro and stone mastic asphalt mixtures showed a similar behaviour as the dense grade asphalt concrete in the previous study. Regarding the control of rutting, a LSV limit of 500 Pa.s was found for original asphalts, while 2,000 Pa.s was the limit for aged asphalt binders. The model to predict the rutting performance of asphalt mixtures was amplified, incorporating both original and aged asphalt LSVs as appropriate input data.