Self Healing Capacity of Asphalt Binders

To test self healing capability of asphalt binders,three asphalt specimens（pure asphalt,modified asphalt and aged asphalt） were prepared.Every specimen was tested by dynamic shear rheometer（DSR）.The temperature sweeps result indicates that both aging and SBS modifying influence the self healing capability of asphalt binder.The fatigue-heal-fatigue test was introduced to study the self healing capability of asphalt in its serving periods.Furthermore,three different periods（0.5 h,1 h,3 h） were set up to study the influence of rest time on fatigue time.It is concluded that longer rest time,less load will delay the appearance of cracks and extend the service life of asphalt binders.

Microstructure Morphologies of Asphalt Binders using Atomic Force Microscopy

We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.

Review of ultraviolet ageing mechanisms and anti-ageing methods for asphalt binders

Asphalt binder is inevitably aged by ultraviolet(UV)light during its service period.UV ageing can significantly decrease the technical properties of asphalt binder.The sensitivity of asphalt to UV ageing and thermal-oxidative ageing differs,such that the UV ageing performance cannot be determined based on the thermal-oxidative ageing performance.Previous researches mainly focused on the chemical composite and technical performance changes of asphalt binder during UV ageing,and the UV light parameters effect on the ageing rate of asphalt binder.However,the theory for characterizing and explaining the development of UV ageing depth does not get too much attentions,and the UV ageing mechanism of asphalt binder is not very clear.Therefore,it cannot guide to develop or select the good methods or anti-UV ageing additives for asphalt binders.This paper focuses on the latest researches of the mechanisms and anti-ageing methods of asphalt binders.With the increase of UV ageing time,the UV ageing of asphalt binder develops gradually from the surface to inner part.There are various methods,such as low-penetration grade asphalt,less air void ratio,UV stabilizers and UV light absorbers,that can improve the UV ageing resistance of asphalt binders.A new theory of sensitive wavelengths of asphalt UV ageing is proposed,which can enrich the basic theory of asphalt UV ageing.Depending on this theory,different wavelengths of UV light have different ageing effects on asphalt binder.The composite anti-UV ageing additives with barrier and specific absorption effects on UV light is proposed,and may have better improvement effect on the anti-UV ageing performance of asphalt binder.

Effect of Various Additives on the Low Temperature Performance of Petroleum Based Asphalt Binders

Transverse cracking is a prevalent problem that occurs in asphalt pavement binders in cold climates and diminishes the integrity of the road as well as shortens the life span of the road leading to premature failure.Current specification for testing petroleum asphalt binders for transverse and low temperature cracking is not elaborate enough to accurately model the engineering behaviour of the binders.Besides,neat asphalt derived from petroleum crude oil does not seem to perform well at certain low temperatures without some modification to it.Thus,a study was to be undertaken to determine the low temperature behaviour of 60-70 penetration neat binder modified with traditionally used materials such as Crushed Lime Stone Powder(CLP),Hydrated Lime(HL)and Cellulose Oil Palm Fiber(COPF)at temperatures 0°C,-5°C and-10°C.The study was carried using the state of the art Bending Beam Rheometer(BBR)to assess the stiffness value,m-value and deflection level.The tests were performed in accordance with AASHTO T 313-12 specification.The results of the penetration,rotational viscosity and softening point showed that all of the modified binder specimens are within the required range.However,the performance assessments on the modified petroleum binders with additive materials showed a varied nature with CL powder being the best and the COPF the lowest.It was also observed that the crushed lime stone powder had an increase in stiffness,reduction in deflection and m-value.

Linear viscoelastic behavior of asphalt binders and mixtures containing very high percentages of reclaimed asphalt pavement

The primary aim of this study is to correlate the impact of aggregates,if any,on the viscoelastic behavior of rejuvenated asphalt mixtures containing very high amounts of reclaimed asphalt pavement(RAP)(>50%).First,gradation of 100%RAP was rectified,using a modified Bailey method by adding virgin aggregates to achieve two coarse dense-graded and one fine dense-graded blends.Complex modulus test was then performed from−35 to+35℃and 0.01–10 Hz.In addition to performance grade(PG)testing,extracted and recovered binders from different asphalt mixtures underwent shear complex modulus test within−8℃to high temperature PG and frequencies from 0.001 to 30 Hz.Cole−Cole,Black space,complex modulus and phase angle master curves were constructed and ShiftHomothety-Shift in time-Shift(SHStS)transformation was used to compare the linear viscoelastic behavior of asphalt binders and mixtures.The influence of aggregates on the viscoelastic behavior of asphalt mixtures depends on temperature and/or frequency.The role of asphalt binders in the behavior of asphalt mixtures is more pronounced at high temperatures and the effect of the aggregate structure increases as the temperature falls.The maximum difference(60%to 70%)in the viscoelastic behavior of the binder and mixture based on SHStS transformed Cole−Cole curves is within the phase angle of 15°–20°.

Virtual strain loading method for low temperature cohesive failure of asphalt binder

Cohesive failure is one of the primary reasons for low-temperature cracking in asphalt pavements.Understanding the micro-level mechanism is crucial for comprehending cohesive failure behavior.However,previous literature has not fully reported on this aspect.Moreover,there has been insufficient attention given to the correlation between macroscopic and microscopic failures.To address these issues,this study employed molecular dynamics simulation to investigate the low-temperature tensile behavior of asphalt binder.By applying virtual strain,the separation work during asphalt binder tensile failure was calculated.Additionally,a correlation between macroscopic and microscopic tensile behaviors was established.Specifically,a quadrilateral asphalt binder model was generated based on SARA fractions.By applying various combinations of virtual strain loading,the separation work at tensile failure was determined.Furthermore,the impact of strain loading combinations on separation work was analyzed.Normalization was employed to establish the correlation between macroscopic and microscopic tensile behaviors.The results indicated that thermodynamic and classical mechanical indicators validated the reliability of the tetragonal asphalt binder model.The strain loading combination consists of strain rate and loading number.All strain loading combinations exhibited the similar tensile failure characteristic.The critical separation strain was hardly influenced by strain loading combination.However,increasing strain rate significantly enhanced both the maximum traction stress and separation work of the asphalt binder.An increment in the loading number led to a decrease in separation work.The virtual strain combination of 0.5%-80 provided a more accurate representation of the actual asphalt's tensile behavior trend.

Compound Rejuvenation of Polymer Modified Asphalt Binder

The objective of this research was to show a way to conduct rejuvenation of aged polymer modified asphalt binder（PMB） successfully.To fully evaluate and understand the rejuvenation of aged PMB,the Penetration grade tests including penetration,soften point,ductility and elastic recovery and SuperpaveTM PG grade tests including DSR,BBR and DDT were conducted.The rejuvenation effect of aged PMB by utilizing a fluid recycling agent in common use for binder rejuvenation was evaluated.And then the compound rejuvenation effect of aged PMB by utilizing the recycling agent with a new modifying additive for binder modification was evaluated.The experimental results indicated that the recycling agent in common use currently does not apply to polymer modified asphalt binder rejuvenation.But the recycling agent together with the modifying additive can restore the characteristics of aged polymer modified binder very well.Therefore,compound rejuvenation of polymer modified asphalt binder is recommended.

Property of Anti-Ultraviolet Aging of LDHs Modified Asphalt

LDHs was introduced into 70# asphalt binder by different weight ratio. Asphalt penetration test, soft point test, ductility test, viscosity test, dynamic shear rheometer（DSR） test and Fourier transform infrared（FTIR） test, were conducted to characterize and predict the LDHs modified asphalt. Research results indicated that the LDHs has great effect on resistance to UV of asphalt, which makes the asphalt absorb less ultraviolet radiation under the same UV intensity. Complex modulus, phase angle and FTIR test results indicate that the LDHs can significantly enhance the property of anti-ultraviolet aging of asphalt. The test results show that the LDHs has an obvious improvement on the anti UV aging of asphalt.

Cross-scale Correlation of Macro-micro Evaluation Indexes for Asphalt Binder

In order to further study the reliability of macro evaluation indexes,molecular dynamics (MD) was applied to the evaluation of asphalt binder.Micro evaluation indexes (potential energy,surface free energy,solubility parameter and diffusion coefficient) of asphalt binder in different service phases (virgin,modified,aged and rejuvenated) were simulated.Combined with the variation characteristics of asphalt binder macro evaluation indexes (permeability,ductility,viscosity and softening point) in different service phases,the cross-scale correlation of macro-micro evaluation indexes was explored.The results show that the macro and micro evaluation indexes of asphalt binder have different characteristics in different service phases.The essence of the variation in the properties of asphalt binders is the difference in micro composition.In addition,there is a certain correlation between macro and micro evaluation indexes,which can be described by the gray relation theory.The cross-scale correlation of macro-micro evaluation indexes can provide a certain theoretical basis for the development of asphalt binder.

Chemical and rheological analysis of unaged and aged bio-extended binders containing lignin

The use of alternative renewable sources to totally or partially replace bitumen is one of the most current challenges in the road pavement sector.The growing energy cost and environmental concerns lead to the necessity to find alternative solutions,by supporting at the same time sustainability and circular economy principles.Within this framework,this paper presents the application of a powder lignin,a natural bio-polymer deriving from byproducts of wood pulp and paper industry,to replace part of bitumen.The bituminous blend consisting in 70%of bitumen and 30%of powder lignin(by weight)was made in laboratory through the use of a high shear stirring mixer,and a reference plain bitumen characterized by a similar consistency(i.e.,same penetration grade)was used as comparison.Then,an extensive investigation on chemical and rheological properties of the bio-binder is presented.Fourier transform infrared spectroscopy(FTIR),saturates,aromatics,resins and asphaltenes(SARA),bending beam rheometer(BBR),frequency sweep tests and multiple stress creep recovery tests(MSCR)with a dynamic shear rheometer(DSR)were performed.Moreover,unaged,short-and long-term aging conditions were considered.Results indicated that powder lignin dominates the rheological behavior of the bio-binder and,from chemical analysis,it seems that it partially acts as a filler and partially as a binder.This would result in improved performances at both low and high temperatures,leading to a wider temperature range of performance grade(PG).Moreover,despite a stiffening effect is recognized,lignin also offers an antioxidant potentiality,reducing the aging susceptibility of the investigated bio-binder.

A state-of-the-art review on interfacial behavior between asphalt binder and mineral aggregate

The interface between asphalt binder and mineral aggregate directly affects the service life of pavement because the defects and stress concentration occur more easily there. The interaction between asphalt binder and mineral aggregate is the main cause of forming the interface. This paper presents an extensive review on the test technologies and analysis methods of interfacial interaction, including molecular dynamics simulation, phase field approach, absorption tests, rheological methods and macro mechanical tests. All of the studies conducted on this topic clearly indicated that the interfacial interaction between asphalt binder and mineral aggregate is a physical-chemical process, and can be qualitatively characterized by microscopical technique （such as SEM and AFM）, and also can be quantitatively evaluated by rheological methods and interfacial mechanical tests. Molecular dynamics simulation and phase field approach were also demonstrated to be effective methods to study the interfacial behavior and its mechanism.

Evaluation of fatigue and rutting properties of asphalt binderand mastic modified by synthesized polyurethane

Fatigue and rutting phenomena are major distresses in asphalt pavements.Asphalt mixture properties are highly dependent upon the asphalt binder and the mastic behavior.The purpose of this study was to investigate the behavior of the asphalt binder and the mastic,modified by the synthesized polyurethane,at high and intermediate temperatures.The filler/asphalt binder ratio(by weight)was 1.0.The dynamic shear rheometer(DSR)was used to measure fatigue(G^(*)sinδ)and rutting(G^(*)/sinδ)parameters.In this study,the multiple stress creepandrecovery(MSCR)testwasalso utilizedto calculate the ruttingpotential of theasphalt binder and themastic.Parameters of the non-recoverable compliance(Jnr)and the percentage recovery(%)were evaluated at high temperatures.The obtained results indicated that the synthesizedpolyurethaneimproved the ruttingandfatigue properties.Therewasa significant correlation between the asphalt binder and the mastic in terms of the complex modulus(R^(2)=0.9958),rutting(R^(2)=0.9944),and the non-recoverable compliance(R^(2)=0.9707).For the fatigue parameter(R^(2)=0.9852),the complex modulus(R^(2)=0.9855),and the phase angle(R^(2)=0.8262),significant relationships were observed between the asphalt binder and mastic samples at intermediate temperatures.Overall,the chemical reaction between the filler and the asphalt binder could be effective in different behaviors of the mastic and asphalt binder.Therewasa 112%-164%increase in the G^(*)sinδparameter formastics,compared to that of the asphalt binder.The complex modulus was 6 times higher by adding the filler content.

Fatigue of asphalt binder,mastic and mixture at low temperature

The fatigue damage is one of the most common distresses observed on the asphalt concrete pavement.To thoroughly understand the fatigue of asphalt concrete,the behaviors of the major components of asphalt concrete under cyclic loading are investigated respectively in this study.A new experiment method is developed to evaluate the performances of asphalt binder,mastic and fine aggregates mixture under cyclic tensile loading.The fatigue test results of asphalt binder show that the fatigue performance of asphalt binder is closely related with loading magnitude,temperature and loading rate.Mastic specimens with different filler content are tested and the results indicate that mastic specimens with 30%filler content show better fatigue resistance and higher permanent strain.The micro-structure analysis of mastic and mixture indicates that the fatigue resistance is closely related with the air void content of specimen.3D digital specimens are developed to model the fatigue of the asphalt binder,mastic and mixture specimens based on the finite element method(FEM).Fatigue damage of asphalt concrete is simplified by a damage model.With proper selection of damage parameters,the simulation results agree well with laboratory test results and can be used as a basis for future fatigue research.

Molecular dynamics simulation on the rejuvenation effects of waste cooking oil on aged asphalt binder

Waste cooking oil(WCO)has received attention on rejuvenating aged asphalt binder widely in recent years.This study evaluated the rejuvenation effects of WCO on aged asphalt binder on the micro-scale using molecular dynamics(MD)simulation.First,the representative molecules of WCO and asphalt binders were selected.The molecular mixture model was then developed.The thermodynamic properties were investigated,including density,cohesive energy density,solubility parameter,and surface free energy.The results show that WCO can restore the thermodynamic properties of aged asphalt binder to some extent and WCO has different influences on electrostatic interactions and van der Waals effects.From the diffusion behavior and molecular structure of asphalt binder,WCO can improve the molecular mobility and restore the colloidal structure.Besides,the adhesion work and moisture susceptibility of asphalt binder-aggregate interfaces(calcite and quartz)were evaluated.The results show that WCO can improve adhesion work between asphalt binder and aggregates since WCO can change molecular structure of asphalt binders and certain adhesion work exists between WCO and aggregates.Also,it can mitigate the moisture susceptibility of asphalt binder-aggregate interfaces(calcite and quartz).The study demonstrates that the MD simulation can help to understand the rejuvenation effects of WCO on aged asphalt binder on the micro-scale.

Laboratory investigation of emulsified asphalt binder modified with wood-derived nano-cellulose and nano paper-cellulose

Emulsified asphalt is the primary material for preventive maintenance and cold-mix paving,but its low cohesive strength and poor mechanical properties limit its wide application,even with polymer modification.In this study,Styrene-Butadiene Rubber(SBR)emulsified asphalt was modified with nano-cellulose materials,namely nano paper-cellulose(NPC)and wood-derived nano-cellulose(WDC),to improve its properties.A novel preparation method of nano-cellulose solution was developed,including blending,ultrasonic stirring,and centrifugal treatment.Four types of nano-cellulose solution(0.5%NPC,0.5%,1.0%,and 1.5%WDC by weight of water)were selected.The microscopy analysis indicated that 0.5%WDC emulsion had a smaller particle size than 1.5%WDC emulsion.The rheology test indicated that WDC modified residue improved rutting resistance with the increased solution dosage due to the cross-linking effect,but its creep-and-recovery performance was worse than that of SBR emulsion residue.The NPC modified binder had a higher rutting factor than WDC modified binder at the same dosage after short-term aging.In addition,1.0%WDC could be regarded as the optimal dosage in terms of fatigue and low-temperature performance.Furthermore,Fourier Transform Infrared Spectroscopy(FTIR)results showed that 0.5%NPC modified residue performed better in long-term aging resistance compared with 0.5%WDC modified asphalt.

New innovations in pavement materials and engineering:A review on pavement engineering research 2021

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges.In the past 10 years,the pavement infrastructure strongly supports the rapid development of the global social economy.New theories,new methods,new technologies and new materials related to pavement engineering are emerging.Deterioration of pavement infrastructure is a typical multi-physics problem.Because of actual coupled behaviors of traffic and environmental conditions,predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis.In order to summarize the current and determine the future research of pavement engineering,Journal of Traffic and Transportation Engineering(English Edition)has launched a review paper on the topic of"New innovations in pavement materials and engineering:A review on pavement engineering research 2021".Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering,this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world.The content includes asphalt binder performance and modeling,mixture performance and modeling of pavement materials,multi-scale mechanics,green and sustainable pavement,and intelligent pavement.Overall,this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.