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.

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.

Rheological Evaluation of Polymer Modified Asphalt Binders

The microstructure and dynamic rheological characteristics of asphalt containing different polymer modifiers （crumb rubber, styrene-butadiene-styrene and crumb rubber mix with styrene- butadiene-styrene） at mid and high service temperature levels were investigated by using scanning electron microscopy（SEM）, dynamic shear rheometer（DSR） and repeat creep test. The main objective of the investigation was to rank the modifiers based on their effect on performance characteristics of asphalt under service conditions. To evaluate the effect of different modifiers on the viscoelastic response of asphalt, the temperature and frequency dependences of the dynamic viscoelastic properties were compared. The mid-temperature fatigue resistance and high-temperature rutting resistance of three polymer modified asphalts were evaluated to predict their field performance in roads. Based on the current results, an improved rutting factor was proposed to determine the rutting resistance of asphalt pavements. In addition, the viscous stiffness （Gv）, defined as the reciprocal of viscous compliance, was used to evaluate the high-temperature deformation resistance of asphalt mixtures. The experimental results indicate that the asphalt containing crumb rubber only shows superior performance at mid and high service temperatures in all three modified asphalt binders due to the action of the crumb rubber.

Review on laboratory preparation processes of polymer modified asphalt binder

Several previous studies have documented the progress in polymer modified asphalt binder with respect to materials'types and properties.However,limited or no effort was made to document findings on the laboratory preparation practices of polymer modified asphalt binder.Full and clear disclosure of asphalt blend preparation method is necessary for research continuity,reproducibility,and accurate adaptation by future studies for analogy and reliable conclusions.The laboratory preparation processes of various modified asphalt binders have been reviewed in this study.Factors affecting the optimal mixing of asphalt-polymer blends were summarized.The optimal mixing conditions associated with different asphalt modifiers were documented.Gap in the literature on the current practice for the preparation and reporting of various modified asphalt binder was discussed.Modifiers include styrene butadiene styrene(SBS),polyethylene(PE),waste tire rubber or crumb rubber(CR),ethylene vinyl acetate(EVA),sulfur,polyphosphoric acid(PPA),epoxy,polyurethane,nano-materials,etc.Currently,there is lack of modern innovative approached in the preparation of modified asphalt towards better performance.There is no clear standardized definition of term associated with asphalt binder preparation process.Given the limited and common types of polymers utilized for the modification of asphalt binder,it is possible to standardize the mixing procedure for several polymers.Doing so could ease research continuity and facilitates accurate comparison of new studies with earlier ones.

Molecular dynamics simulation and microscopic observation of compatibility and interphase of composited polymer modified asphalt with carbon nanotubes

Interfacing and compatibility are the most challenging issues that affect the performance of polymer modified asphalt.Mechanisms of interfacial enhancement among four base asphalt components(asphaltenes,resins,aromatics,and saturate),styrene-butadiene-styrene(SBS),and carbon nanotubes(CNTs)were investigated by molecular dynamics simulation,with the aim of understanding the key parameters that control the compatibility of CNTs and interphase behavior on the molecular scale.The compatibility of SBS-modified asphalt(SBSMA)was simulated based on self-assembly theory using indexes of binding energy,mean square displacement,diffusion coefficient,and relative concentration distribution.The interphase behavior and microstructure were observed by fluorescence microscopy and scanning electron microscopy.In addition,a rutting experiment was used to verify the molecular dynamics simulation based on macroscopic performance.The results showed that after adding CNTs,the binding energy of the SBS and aromatics increased from 301.8343 to 327.1102 kcal/mol.The diffusion coefficient of the SBS and asphaltenes decreased more than 3.2×10-11 m2/s,and the correlation coefficients between the diffusion coefficient and the molecular weight,surface area and volume were all lower than 0.3.Relative concentration distribution curves indicated that CNTs promote the ability of SBS to swell.Microscopic observations demonstrated that the swelling ability of SBS was increased by CNTs.Overall,the interphase of SBSMA was improved by the additional reinforcement,swelling,and diffusion provided by CNTs.Finally,the rutting experiment found that no matter what the temperature,the rutting factor of CNT/SBSMA is higher than that of SBSMA,which corroborates the findings from the molecular dynamics simulations.

Physical and Thermo-Oxidative Characterization of Asphalt Modified with High Density Polyethylene and Recycled Engine Oil

Modification of asphalt using polymers, oils and other additives has been an option to improve asphalt pavement performance and extend its lifespan. The present work aims to evaluate the influence of the addition of engine oil on the consistency and thermal properties of HDPE-modified asphalt. For this study, compositions containing asphalt, engine oil and high-density polyethylene (HDPE) were prepared, varying the concentration of engine oil by 2.5 wt%, 5 wt%, 7.5 wt% and 10 wt% and keeping the concentration of HDPE at 5 wt%. The samples were characterized by conventional tests of penetration, softening point and viscosity, aging in a Rotational Thin Film Oven (RTFO), Thermogravimetric Analysis (TGA). According to the results, the addition of HDPE to virgin asphalt causes an increase in the consistency of the virgin asphalt, which then decreases linearly as the engine oil is added into the matrix. Conventional tests showed improvements in the applicability of the asphalt in terms of resistance to cracks and permanent deformation. TGA showed a slight increase in stability for the modified asphalt samples at elevated temperatures. The RTFO showed mass gain and loss for samples with and without engine oil, respectively.