| The traditional research focuses on the the study of the single material and the mix ratio. The interface between different matierials is usually neglected because of the difficulty of characterization and complexity. But the practical experience shows that interface usually directly affects the service life of pavement because the defects and stress concentration occurr more easily there. The interaction between asphalt binder and mineral aggregate is the main cause of forming the interface. For these reasons, this research studied the interface behavior and the mechanism in asphalt mixtures from multiple dimensions(mm, μm, nm), and various technologies including macroscopic interface testing, dynamic mechanical analysis, physical and chemical characterization and molecular dynamics simulation were used. The main contents are summarized as follows:First, the adsorption behavior of asphalt on the surface of aggregate was studied at nano scale. Molecular dynamics simulation technology was used to build the models of four asphalt components and five kinds of typical minera l aggregate crystals. The reliability was verified. The asphalt- mineral aggregate interface system model was furtherly built. The interface adsorption and diffusion behavior was studied. The results showed that Van der Waals force was dominant in the adhesion work, while coulomb electrostatic force was weak. The influence rank of mineral aggregate composition on the adhesion work was: Ca O>Mg O>Si O2>Al2O3>Fe2O3. The influence rank of four asphalt components on the adhesion work was: aromatics>asphaltene>resin>saturate. At a reasonable temperature range, the adhesion work between four asphalt components and mineral aggregate increased with temperature increasing. Increasing the temperature can accelerate the diffusion of asphalt components molecular s. The diffusion speed of asphalt components on the surface of Al2O3 was faster than other mineral crystals. The temperarure sensitivity of diffusion coefficient of asphalt components on the surface of Ca O was the maximum. The diffusion speed of asphalt components ranked roughly as their molecular weight: saturate>aromatics>resin>asphaltene. Increasing temperature can make asphalt four components distribute more uniformly. Interaction led to that the concentration peaks of four asphalt components in the vertical direction of aggregate surface were higher than the parallel direction. The distribution of peak positions can verify the colloid structure model of asphalt: the asphalt micelles were formed by resin attaching asphaltene, and then dispersed in the light components.Second, the absorption behavior of asphalt on the surface of aggregate was studied at micro scale. The criterion of demarcation between fixed asphalt and free asphalt was proposed based on micro- and nano-characterization technology. The typical structures were separated by testing and the mechanical and chemical analysis was further conducted. The mechanism of interaction between asphalt and mineral aggregated was explored. The results showed that the thickness of fixed asphalt was around 1 μm. The modulus of asphalt within this thickness increased rapidly, and the bee-structure disappeared. The toluene can disperse the composition structure of asphalt, accelerate the aging of asphalt, to increase the complex modulus of asphalt. The contribution of mineral fillers on the complex modulus of asphalt mastics was mainly due to the particle strength. The effect difference of various materials depended on the interaction between asphalt and mineral fillers. The change of modulus resulting from the interafacial interaction was more significant at high temperature or low frequency. The mineral fillers preferred to absorb the polar component of asphalt, such as asphaltene. The adsorption ability of limestone was stronger than granite. The physical property(eg. specific surface area) of mineral fillers was the main factor effecting the adsorbed asphalt mass. The chemical property(eg. mineral components) affected the adsorbed asphalt layer thickness.Third, the evaluation method of interaction between asphalt and mineral fillers was studied at micrometer scale. The rheological parameters of asphalt and asphalt mastics were tested through dynamic mechanical analysis. The interaction degree between asphalt and mineral fillers were calculated. The interaction parameters were compared and improved. The effect factors of interaction were analyzed. The relationship between interaction and viscoelastic properties of asphalt mastics was built. The results showed that the improved interaction parameter C value based on Palierne model had a better sensitivity and statistical significance. Increasing temperature, or increasing the polar component content, or increasing the specific surface area, or making the particle size composition of mineral fillers finer, or decreasing the content of Si O2 in aggregate can all enhance the interaction between asphalt and mineral fillers. At 25℃-45℃, there was a extremely significant correlation between interaction and complex modulus, rutting factor, and fatigue factor of asphalt mastics. At 15 ℃ and 55 ℃, the correlation was significant. Only at 25 ℃ and 35 ℃, the phase angle had a significant correlation with C value.Fourth, the interface behavior between asphalt and aggregate were studied at the millimeter scale. A testing system evaluating the interface interaction between asphalt and aggregate was developed. The evaluation indicator IP was proposed and its effectiveness was verified. The quantitative evaluation of interaction between asphalt and aggregate was realized. The effect factors of interaction between asphalt and aggregate(or artificial recycled aggregate) were studied. The correlation between interaction and interfacial performance was analyzed. The results showed that increasing temperature or extending the interfacial interaction time can enhance the interaction ability between as phalt and artificial recycled aggregate. The interaction degree between asphalt and fresh aggregate increased first, and then decreased with service time increased. The maximum interaction between asphalt and limestone aggregate was stronger than granite. When the test frequency was 5Hz or 1Hz, there was a significant correlation between interaction and interface shear resistance performace.Finally, the correlation between nanometer scale, micrometer scale and millimeter scale was studied. The adhesion works between asphalt binder and mineral aggregate at molecular scale, filler scale and aggregate scale were obtained by molecular dynamic simulation and surface free energy method. The correlation of adhesion work at different scales was analyzed. The interfacial interaction degrees between asphalt binder and fillers and aggregate were obtained by dynamic mechanical analysis and interfacial test system. The correlations between interfacial adhesion work and interaction were obtained at filler scale and aggregate scale. The correlation between interfacial interaction between filler scale and aggregate scale was analyzed. The results showed that the adhesion work would enlarge 2.64 to 2.68 times from nano scale to filler scale, enlarge 2.08 to 3.16 times from nano scale to aggregate scale. There was a correlation between interfacial ineteraction parameter C value of per specific surface area and interfacial adhesion work. There was a correlation between C value and IP value. IP value was more sensitive than C value. |
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