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In this research, to study the effect of a high-speed shearing method on asphalt aging, based on SK-70# matrix asphalt, the influences of the shear time, shear rate, shear temperature, shea...

In this study, graphene-modified asphalt (GMA) was prepared from SK-70# matrix asphalt and ethylene bis(stearamide) (EBS). Based on the uniform design method, a model was created using Data Processing System (DPS) software and First Optimization (1stOpt) software using the graphene mixing amount, EBS mixing amount, shear rate, shear time, and shear temperature as factors and using the asphalt penetration, softening point, force ductility, SHRP-PG test, and multistress creep recovery data as indices. Calculations and analysis showed that the optimal composition and preparation parameters of GMA are as follows: the graphene proportion is 20&permil, the EBS proportion is 1%, the shear rate is 6000 r.p.m., the shear time is 180 min, and the shear temperature is 140 &deg, C. The prepared GMA had a significantly improved softening point, low-temperature fracture energy, antirutting factor, and creep recovery rate, indicating that adding graphene can improve the high- and low-temperature performance of asphalt. The prepared GMA was characterized by X-ray diffraction (XRD). The dispersibility of graphene in asphalt was evaluated by fluorescence microscopy and Image-Pro Plus imaging software. The results show that graphene can exist in asphalt in a stable form, which increases the loose-layered structure of stacked asphalt or gum. The intense adsorption effect of graphene strengthens the ordered structure of asphalt. However, due to its dispersibility characteristics, some graphene exists in asphalt in clustered form. When the graphene-to-dispersant ratio approaches the optimal value, the dispersant changes the form of graphene in asphalt from irregular clusters to regular clusters and from large, distinct clusters to small, indistinct clusters. When dispersant cannot uniformly disperse graphene in asphalt, graphene clusters primarily form medium-sized grains.

The main purpose of this paper is to develop high-performance graphene-modified asphalt (GMA) and characterize graphene occurrence in asphalt and examine its mechanism. The main research methods are: Based on Lambert-Beer law and dispersants dipropylene glycol dimethyl ether (DME) and polyvinyl pyrrolidone (PVP), the absorbance of dilute graphene mother liquor (GML) solutions at different concentrations were obtained via ultraviolet/visible spectrophotometry, and the concentration of dilute GML solutions were obtained via supernatant algorithms. The absorbance and concentration of dilute GML solutions were fitted via regression, which obtained the absorbance coefficient. Then, based on nominal graphene dosage (G) and dispersant and graphene proportion (D/G), respectively, the absorbance coefficients were fitted via regression to establish mathematical GML materials composition models which were solved via First Optimization (1stOpt) analysis software. Following the materials composition, DME-GMA and PVP-GMA was prepared, and the corresponding performance tests were carried out, and GMA was characterized via metallographic microscope and micro/nano-CT scanning to explore the morphology of graphene and mechanism in asphalt. The results are: Based on dispersants DME and PVP, respectively, the materials composition are G = 0.53%, D/G = 160%, and G = 0.26%, D/G = 190%. The penetration, non-recoverable creep compliance at 0.1 kPa and 3.2 kPa of DME-GMA and PVP-GMA (based on matrix asphalt) were decreased by 7.44 and 7.76%, 20.82 and 30.95% (0.1 kPa), and 8.63 and 18.88% (3.2 kPa), respectively. The softening point, maximum force at 5 °C, ductility at 5 °C, fracture energy at 5 °C, antirutting factors at 64 °C, and creep recovery rate at 0.1 kPa and 3.2 kPa were increased by 4.57 and 7.17%, 41.96 and 61.29%, 14.91 and 18.30%, 55.51 and 98.81%, 17.26 and 40.51%, 646.77 and 867.88% (0.1 kPa), and 128.62 and 153.53% (3.2 kPa), respectively. The high- and low-temperature stability of GMA are notably improved via uniformly dispersing graphene in asphalt materials, and graphene occurs as agglomerates in asphalt materials, and dispersants DME and PVP increase the graphene agglomerate dispersion effect in asphalt materials, changing its larger, irregular morphology to a smaller, regular one. The better the graphene dispersion effect is, the better the GMA performance is. PVP-GMA attains a better performance than DME-GMA.