Experimental Study of Rubberized Asphalt Emulsion Modified Portland cement concrete

The poor fatigue properties and high rigidity of cement asphalt emulsion treated mis(CETM) have for a long time been problems restricting its further development making it impossible for C-ETMto be used as surface layer materials. In this paper, a new kind of cement asphalt emulsion composite-rubberized asphalt emulsion modified Portland cement concrete (RACC) was proposed, which was formed by dispersing rubberized aSPhalt emulsion coated coarse aggregates into cement mortar matrix. In order to evaluate systematically the performance of RACC, laboratory tests with nearly one thousand SPecimen were conducted for resilient modulus, fatigue properties, ultimate ban and length,abrasion, temperature contraction, and dry shrinkage. The experimental results show that the problems existed in C-ETM have to a great extends been solved by RACc. To verify the field performance and inquire into paving technology, teSt road appearsatlsfactory it is concluded that when thed ape surface laycr of semi-rigid base course, RACC is more for surface layer material than both Portland cement concrete(PCC) and asphalt concrete(AC)

Mix design method of asphalt rubber open-graded friction course and its application in overlay

The mix design method of asphalt rubber open-graded friction course （AR-OGFC） by the Marshall test and key technologies of AR-OGFC overlay are studied. Based on the draindown test, the stripping test and the Marshall test by different beating times, the asphalt content estimating method and Marshall beat criterion are studied. It is found that the asphalt content of AR-OGFC can be estimated by the formula of Arizona, and the proper Marshall test criterion for AR-OGFC is 50 beats on both sides. By analyzing the influence of gradation on OGFC performance, the gradation of AR-OGFC is recommended, and the amount of aggregate passing 4. 75 mm should be minimized for AR-OGFC. Through investigation of AR-OGFC overlay projects, key technologies such as the treatment of underlying pavement and the selection of tack coat are advanced, and modified emulsified asphalt should be used in AR-OGFC overlay tack coat.

Microscopic and Dynamic Rheological Characteristics of Crumb Rubber Modified Asphalt

A test for crumb rubber modified asphalt containing 20% crumb rubber particles（30 mesh） was performed using a scanning electron microscope（SEM）.The experimental results indicate that the crumb rubber particles are evenly distributed in the asphalt.Shear rate sweep and shear-temperature sweep tests on the crumb rubber modified asphalt at-20-80 ℃ using a dynamic shear rheology（DSR） instrument,were carried out.The tests show that the complex modulus decreases with increasing temperature;at equivalent temperature,higher load frequencies lead to a larger complex modulus,and this value increasingly decreases as the temperature increases;the phase angle increases with temperature and decreases as the load frequency increases.It can be concluded that the rutting resistance limiting temperature of crumb rubber modified asphalt is 78 ℃,and the anti-fatigue limiting temperature is 16 ℃,which shows that the asphalt has preferable rutting resistance characteristics at high temperature,as well as anti-fatigue characteristics.In addition,the complex modulus master curve at different temperatures was plotted according to the time temperature equivalence principle,which allows the study of the dynamic state behavior of crumb rubber modified asphalt at a wide range of load frequency.

Warm asphalt rubber:A sustainable way for waste tire rubber recycling

Recycling end-of-life tire rubber as asphalt modifier is known as a sustainable paving technology with merits including enhanced pavement durability,waste tire consumption and noise reduction.However,the criticisms on the high construction emissions of asphalt rubber(AR)have limited its application.Warm mix asphalt(WMA)effectively reduces the mixing and compaction temperatures of conventional hot mix asphalt mixtures.The combination of AR and WMA,called warm asphalt rubber(WAR),is a promising paving material which achieves pavement sustainability from principles to practices.Many studies have demonstrated that WMA technologies work effectively with AR pavement in different ways,alleviating the concerns of potential higher emissions of AR by decreasing mixing and paving temperatures.A comprehensive literature review about WAR brings a better understanding of this promising paving technology.The findings of 165 publications were summarized in this review.It summarized the recent developments of WAR in various aspects,including rheological properties,mix design,mixture mechanical performance,field application,construction emission,and asphalt-rubber-WMA additive interaction.It is expected that this review is able to provide extensive information to explore further research development and application of WAR.

Creep Characteristics of Crumb Rubber Modified Asphalt Binder

Crumb rubber modified asphalt containing 20 percent crumb rubber particles of 30 mesh has been examined by Scanning Electron Microscope （SEM） to observe the microcosmic appearance and the characteristic distribution of crumb rubber particles in asphalt. The SEM pictures reveal that the crumb rubber particles distribute evenly in the asphalt and they are compatible well with asphalt. The shear creep test of crumb rubber modified asphalt was carried out at -10 ℃ and 40 ℃ by Dynamic Shear Rheology （DSR）. The shearing deformation at different temperature and creep stiffness modulus curve at loading stage of crumb rubber modified asphalt have been measured. The stiffness modulus of crumb rubber modified asphalt is much temperature sensitive and it decays much quick at the early stage of loading than normal asphalt. The rate of decay of stiffness modulus is slow at the subsequent stage and stiffness modulus approaches to a stable value at the final stage at a higher temperature. In addition, Burgers model is suitable to describe and simulate experimental results of viscoelastic properties of the crumb rubber modified asphalt.

Laboratory investigation on effects of organic montmorillonite on performance of crumb rubber modified asphalt

In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT content on properties of CRMA were studied.The rutting factor obtained by dynamic shear rheological(DSR)test was adopted to evaluate the high-temperature performance.The creep stiffness and m value determined by the bending beam rheometer(BBR)test were employed to evaluate the low-temperature performance.The softening point,ductility,rutting factor before and after rolling thin film ovens test(RTFOT)and pressure aging vessel test(PAV)were compared to characterize the aging properties.Moreover,the segregation test after being reserved for 48 h and 7 d was conducted,and the softening point and rutting factor of upper and lower layers of segregation pipe were adopted to evaluate the storage stability.The results indicated that the high-temperature performance and anti-aging performance were developed with the increasing content of OMMT,while the low-temperature performance deteriorated.The storage stability was improved with the increasing content of OMMT before the content exceeded 4%,after which the storage stability declined.Taking account of all factors,it is suggested that the optimum content of OMMT is 3%−4%.

Interaction Theory of Asphalt and Rubber

Through scanning electron microscope （SEM）, spectral analysis, and component analysis tests, the interaction theory between asphalt and rubber was discussed. It is concluded that rubber powder become soft and bond together with each other after being mixed with asphalt. The asphalt changes from a smooth homogeneous matter to a continuous mixing system which is composed of rubber powder and asphalt. The interaction is mainly physical diffusion, but there are some chemical reactions in the process, especially at long reaction time.

Influence of Rubber Powder Movement on Properties of Asphalt Rubber from the Mesoscopic View

The research on asphalt performance mainly focused on the macro performance and micro mechanism.Mesoscopic analysis was introduced to study the effect of rubber powder movement on asphalt rubber properties.After the preparation parameters and the preparation process of asphalt rubber were determined,the modification mechanism and rheological properties were analyzed which revealed the compatible stability mechanism.Then,the analysis model of asphalt rubber was established to focus on simulating the effect of rubber powder and the spatial movement on its mechanical properties.The experimental results show that rubber powder can make the asphalt rubber bear more uniform stress distribution and enhance the ability to resist deformation.Meanwhile,the rotational motion and final distribution of rubber powder have an obvious impact on the mechanical properties of asphalt rubber.In the selected feature points,the average stress of rubber powder at 0°space angle is only 34.1%of that at90°space angle.When the rubber powders are all in parallel in the ideal state,it enhances the mechanical properties the most.This study supplements the“mesoscopic”scale between macro and micro research.The relationship between micro mechanism and macro properties of asphalt rubber will be established from the mesoscopic perspective.It is also an effort to realize the effective correlation from micro,mesoscopic to macro in asphalt.

Experimental Survey on Dry Asphalt Rubber Concrete for Sub-ballast Layers

This paper presents the results of an experimental survey on the potential application of DARC （dry asphalt rubber concrete） in rail superstructure, within sub-ballast layers by measuring its damping and mechanical properties. Based on the environmental friendly point of view the DARC has the significant advantage as the backfill material of sub-ballast layer because the rubber comes from the waste tires of truck and its usage can results a significant recycling of non-biodegradable wastes. After a preliminary mix-design of several DARCs, with different rubber content that confirmed by using the Marshall test, the stiffness modulus and damping ratio both of a standard bituminous mixture and of dry asphalt rubber concrete with a rubber content equal to 1.5% were determined using the four points bending device. The experimental results were compared and a numerical analysis by means of a 2D lumped mass model was developed in order to evaluate the different performance within the rail superstructure in terms both of the deflection and of the pressure on sub-grade. Both the results on the mechanical and dissipative properties of the DARC and the mechanical behavior of the correlate rail superstructure encourage the authors to continue the research on the application of such material for sub-ballast layers.

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.

The Viscosity-reducing Mechanism of Organic Wax Additive on CRMA

CRMA was prepared by mixing PG 64-22 asphalt with crumb rubber powder of 40 mesh size and 18% by weight of the asphalt. Sasobit, a typical organic wax additive, was selected and added into CRMA. A series of tests, namely, brookfield viscosity, environmental scanning electron microscope（ESEM）, component test, differential scanning calorimeter（DSC）, fourier transform infrared spectroscopy （FTIR） and nuclear magnetic resonance （NMR） were conducted on CRMA with and without organic wax additive, and microcosmic appearance, component content and molecular structure of various asphalt binders were obtained. The test results indicate that the addition of Sasobit~ into CRMA can effectively change the contents of components： the content of asphaltenes increases relatively, while saturates decreases. In addition, the interaction between various components of CRMA is weakened, and the state of equilibrium between the dispersant and dispersed phase is changed at the same time. That is why the viscosity decreases after the organic wax additive is added into CRMA.

Caltrans use of scrap tires in asphalt rubber products:a comprehensive review

The California Department of Transportation （Caltrans） has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt（RHMA）. Both the wet （field blend） and dry processes were used in early trials. Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility, a terminal blend wet process. Since the beginning of this century, Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound, cost effective, and environmentally friendly strategies for using scrap tire rubber in roadway applications. By the end of year 2010, approximately 31% of all hot mix asphalt （HMA） placed by Caltrans was rubberized HMA, roughly 1.2 million tons. Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development. These included the construction of two full-scale field experiments, five warranty projects, and an accelerated pavement study using a heavy vehicle simulator. Additionally, terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis. This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products. Current practices and future outlook are also discussed.

Evaluation of the compatibility between rubber and asphalt based on molecular dynamics simulation

Using of rubber asphalt can both promote the recycling of waste tires and improve the performance of asphalt pavement.However,the segregation of rubber asphalt caused by the poor storage stability always appears during its application.Storage stability of asphalt and rubber is related to the compatibility and also influenced by rubber content.In this study,molecular models of different rubbers and chemical fractions of asphalt were built to perform the molecular dynamics simulation.The solubility parameter and binding energy between rubber and asphalt were obtained to evaluate the compatibility between rubber and asphalt as well as the influence of rubber content on compatibility.Results show that all three kinds of rubber are commendably compatible with asphalt,where the compatibility between asphalt and cis-polybutadiene rubber(BR)is the best,followed by styrene-butadiene rubber(SBR),and natural rubber(NR)is the worst.The optimum rubber contents for BR asphalt,SBR asphalt,and NR asphalt were determined as 15%,15%,and 20%,respectively.In addition,the upper limits of rubber contents were found as between 25%and 30%,between 20%and 25%,and between 25%and 30%,respectively.

Effect of SBS and crumb rubber on asphalt modification:A review of the properties and practical application

Owing to the environmental protection potential and the desirable high performance capabilities,asphalt rubber(AR)and styrene-butadiene-styrene(SBS)modified asphalt have been widely used.However,the poor construction workability and segregation issues of AR,along with the exorbitant cost of SBS modified asphalt,are of the serious problems that plague their application scope.Moreover,SBS/crumb rubber(CR)modified asphalt is gradually becoming widespread and it therefore becomes incumbent to find appropriate ways to mitigate the issues that may limit its use.As a consequence,it becomes crucial to analyze the interaction between CR and SBS modifiers in the composite mixture,as well as evaluate the influence of modifier dosage on the performance of the modified asphalt.This study presents a comprehensive review of the effects of SBS modifier,CR modifier and composite SBS/CR on the performance of modified asphalts.Macro analysis and micro analysis,including analysis on the conventional physical properties,are carried out.It can uncover the interaction between modifier and asphalt,which reveals how the modifiers influence the properties of modified asphalts.This study will serve as a source of invaluable information to researchers,engineers,and designers,informing them the development,potential and challenges of the CR,SBS and SBS/CR modified asphalts,the optimum contents to attain the best performance along with the mechanism involved.

Aging properties and aging mechanism of activated waste rubber powder modified asphalt binder based on rheological properties and micro-characterization

The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements.This study is performed to develop a novel pavement material using waste rubber powder,waste lubricating by-product(LBP),and asphalt.Subsequently,the aging properties and aging mechanism of activated waste rubber powder modified asphalt(ARMA)are investigated based on its rheological properties and microcharacterization.The rheological results show that,compared with waste rubber powder modified asphalt(RMA),ARMA offers a higher aging resistance and a longer fatigue life.A comparison and analysis of the rheological aging parameters of ARMA and RMA show that LBP activation diminishes the aging sensitivity of ARMA.The microcharacterization result shows that the aging of ARMA may be caused by the fact that LBP-activated waste rubber powder is more reactive and can form a dense colloidal structure with asphalt.Therefore,the evaporation loss of asphalt light components by heat and the damage to the colloidal structure by oxygen during the aging process are impeded,and the thermal-oxidative aging resistance of ARMA is improved.

Green Road Construction Technologies in Guangzhou

Total road pavement in Guangzhou reaches 77×10~6m^2.Its huge maintenance and potential rehabilitation calls for a green road system.This paper presents a discussion,first about green road construction technologies together with their applications and development like reclaimed asphalt pavement,rubberized asphalt pavement,and warm mix asphalt; and then,about the key obstacles for promotion and activities,primarily for green road promotion,in the perspectives of the current technical and application situations in China and separately in Guangzhou.Based on environmental and conditional analysis,as well as a development expectation from an industrial viewpoint,this paper creates a development trend of green road technologies.