Physical-Rheological Properties and Performances of Rejuvenated(Styrene-Butadiene-Styrene)Asphalt with Polymerized-MDI and Aromatic Oil

Traditional asphalt rejuvenators,like aromatic oil(AO),are known to be effective in improving the low-temperature properties and fatigue performances of aged SBS(styrene-butadiene-styrene)modified asphalt(SBSMA)binders and mixtures.However,these rejuvenators inevitably compromise their high-temperature properties and deformation resistances because they dilute asphalt binder but do not fix the damaged structures of aged SBS.In this study,a highly-active chemical called polymerized 4,4-diphenylmethane diisocyanate(PMDI)was used to assist the traditional AO asphalt rejuvenator.The physical and rheological characteristics of rejuvenated SBSMA binders and the moisture-induced damage and rut deformation performances of corresponding mixtures were comparatively evaluated.The results showed that the increasing proportion of AO compromises the hightemperature property and hardness of aged SBSMA binder,and an appropriate amount of PMDI works to compensate such losses;3%rejuvenator at mass ratio of AO:PMDI=70:30 can have a rejuvenated SBSMA binder with a high-temperature performance similar to that of fresh binder,approximately at 71.4°C;the use of AO can help reduce the viscosity of PMDI rejuvenated SBSMA binder for improving its workability;PMDI can help improve the resistance of AO rejuvenated SBSMA binder to deformation,especially at elevated temperatures,through its chemical reactions with aged SBS;moisture induction can enhance the resistance to damage of rejuvenated mixtures containing AO/PMDI or only PMDI;and the rejuvenator with a mass ratio of AO:PMDI=70:30 can lead the rejuvenated mixture to meet the application requirement,with a rut depth of only 2.973 mm,although more PMDI can result in a higher resistance of rejuvenated mixtures to high-temperature deformation.

Thermal Oxidative Aging Characterization of SBS Modified Asphalt

Both macro and micro-methods were introduced to study the physical and chemical properties of thermal oxidative aging of SBS （styrene-butadiene-styrene） modified asphalt. The physical properties of SBS modified asphalt before and after aging were analyzed by normal tests. The structure and quality variation of SBS modified asphalt during the aging process was analyzed by FTIR （Fourier transform infrared spectrum）. FTIR result shows that the degeneration of SBS modified asphalt is mainly caused by oxidative reaction and rupture of C=C double bond. The molecular weight variations of asphalt function groups and SBS polymer were studied by GPC （Gel Permeation Chromatography）. GPC result shows that small molecules transform into larger one in asphalt and SBS polymer molecule degrade during the aging process. SBS polymer may lose its modifying function after long time aging.

Analysis of Aging Mechanism of SBS Polymer Modified Asphalt based on Fourier Transform Infrared Spectrum

The aging mechanism of SBS modified asphalt during its aging process was studied.The characterizations of base asphalt,SBS polymer and its modified asphalt were determined in different aging time by Fourier transform infrared spectrum（FTIR）.FTIR shows that oxidative dehydrogenation reaction occurs in asphalt,and unsaturated carbon bond is generated under short-term thermal aging condition.Additionally,SBS polymer was aged significantly under that condition,the speed of which was faster than that of base asphalt.The aging laws of both asphalt and SBS polymer during the aging process of SBS modified asphalt were similar to their aging laws respectively.Due to the protective effect between asphalt and SBS polymer,the aging degrees of asphalt and SBS polymer were lower than those aged independently.

Quantitative Analysis on Distribution of Modifier in Microstructure of SBS Modifi ed Asphalt

A method was developed to make a quantitative analysis of the microstructure of asphalt modified with styrene-butadiene-styrene block（SBS） copolymer. Moreover, both mixed and branched SBS were employed in the preparation of modified asphalt. By sampling specimens from the top, middle, and bottom, a number of microscope slides were made and 400 times micro images were gained. Binarized with the software of MATLAB, the images then went to the process of distribution test, when four typical distributions were employed to investigate the distribution of modifi er spread in asphalt. The distribution characteristic and its parameter were both found. The results show that asphalt phase clearly obeys Poisson distribution, and its parameter, λ, is bond up with the condition SBS performs in. Based on this parameter, indexes can be set up to evaluate the structure of the mixture and its performance as well. Compared with that modifi ed with mixed SBS, the asphalt modifi ed with branched SBS has better performance but worse stability, for it is easier to segregate.

Influence of Adding Compatibilizer to SBS Polymer-Modified Asphalt on Compatibility and Rheological Behavior

Adding compatibilizer to polymer-modified asphalt(PMA)is an effective method to improve compatibility and performance.However,only few studies have systematically focused on how compatibilizer can affect the performance of styrene-butadiene-styrene(SBS)polymer-modified asphalt(PMA).In this study,six compatibilizers with different compositions were used to prepare SBS PMA samples.Conventional performance,viscosity-temperature characteristics,viscoelastic behavior,creep properties,and morphology were investigated.The results show that adding compatibilizer to SBS PMA has a great effect on its performance.High aromatics content in compatibilizers can improve the high-temperature performance of SBS PMA,while a high saturates content can enhance the low-temperature performance.Additionally,high aromatics content in compatibilizer can increase the temperature sensitivity.While the aromatics content does improve the compatibility of SBS PMA to some extent,adding compatibilizer to SBS PMA has few effects on the microstructure.Judging from our test results,we can conclude that the optimum aromatics content for adding compatibilizer to SBS PMA ranges from 33.21%to 54.22%.

Non-isothermal kinetics of styrene-butadiene-styrene asphalt combustion

The combustion characteristics of styrene-butadiene-styrene （SBS） asphalt are studied by thermogravimetric analysis （TG/DTG） at four different heating rates. According to the saturates/aromatics/resins/asphaltenes （SARA） fractionation method, the combustion process of SBS asphalt can be divided by Gaussian peak fitting into three main stages： oil content release, resin pyrolysis, and asphaltene and char combustion. When the heating rate increases, the mass losses of the oil content and resin pyrolysis increase, and less asphaltenes are formed at a higher temperature. The activation energy values are calculated by the Coats-Redfern method to be in the range 61.6 kJ/mol-142.9 kJ/mol. The Popescu method is used for the kinetic analysis, and the result shows that the three stages of asphalt combustion can be explained by the sphere phase boundary reaction model, the second order chemical reaction model, nucleation, and its subsequent growth model, 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.

Effect of styrene-butadiene-styrene copolymer on the aging resistance of asphalt:An atomistic understanding from reactive molecular dynamics simulations

To reveal the potential influence of styrene-butadiene-styrene(SBS)polymer modification on the anti-aging performance of asphalt,and its mechanism,we explored the aging characteristics of base asphalt and SBS-modified asphalt by reaction force field(ReaxFF)and classical molecular dynamics simulations.The results illustrate that the SBS asphalt is more susceptible to oxidative aging than the base asphalt under oxygen-deficient conditions due to the presence of unsaturated C=C bonds in the SBS polymer.In the case of sufficient oxygen,the SBS polymer inhibits the oxidation of asphalt by restraining the diffusion of asphalt molecules.Compared with the base asphalt,the SBS asphalt exhibits a higher degree of oxidation at the early stage of pavement service and a lower degree of oxidation in the long run.In addition,SBS polymer degrades into small blocks during aging,thus counteracting the hardening of aged asphalt and partially restoring its low-temperature cracking resistance.