Study On Adhesion Properties And Action Mechanism Between Asphalt And Mineral Interface

Adhesion is one of the fundamental properties which is important to the asphalt’s quality,performance and applicability.Adhesive force strength between asphalt and aggregates plays the role that binding the aggregate together.It contribute significantly to the asphalt binder’s overall performance in road pavement.Therefore,more fundamental materials science research is needed to better characterize and predict the service performance of asphalt binders.In this paper,experimental and molecular simulation were used to study the mechanism of the adhesion between the asphalt and the mineral aggregate interface.AFM probe tips were modified with four types of spherical mineral particles and were used to investigate the adhesive forces at mineral particle-asphalt substrate interfaces.This provide a new approach to the investigation of adhesion between mineral particles and asphalt in micro-scale.Results shows the sandstone-substrate group exhibited a larger adhesion value than the other three mineral-substrate groups,while the granite and basalt substrate group exhibited relatively small adhesive forces,and the limestone-substrate group shows the lowest adhesion value.Adhesive forces increase obviously as the Si O₂ content increases.This indicates that physical adsorption has a greater influence than chemical adsorption on the interfacial adhesion properties.Besides,linear models,single-factor ANOVA and IQR analyses were applied for evaluating the distributions of adhesive force values.The adhesive forces differed between minerals,and had good repeatability and reproducibility in the AFM tests.Furthermore,the pull-off test was used to investigate the adhesive forces of mineral block-asphalt interfaces in macroscale.Resin fraction exhibited a larger adhesion value than the other three fractions,while the Asphaltene and Saturate fraction exhibited relatively small adhesive forces,and the Aromatic fraction showed the lowest adhesion value.The nano-level voids or grooves on the surface of the probe prevent the asphalt contacting with the surface of the particles sufficiently.So the mineral probes could not effectively obtain the influences of irregularity on the probe surface in microscale.The particle size of the probe has different effects on the interfacial adhesion.The larger the particle size,the greater the adhesion between the probe and the asphalt interface.The irregularity of the aggregate was the main factor affecting the adhesion properties between the mineral and asphalt.The conventional index of SBS modified asphalt has a partial correlation with the adhesion between the four minerals and asphalt.However,the linking of sulfur with polymer modifiers in the asphalt could not improve the adhesion between asphalt and mineral significantly.In addition,the effect of the number of grooves of the mineral block surface on the interface adhesion property is related to the total area of the contecting mineral surfaces and the slope of the single side of the groove.The ratio of the adhesion force between the mineral-asphalt interface to the uncarved mineral surface is approximately equal to the actual area ratio of the two interfaces and vice versa.Finally,a molecular model of the mineral was constructed based on calcium carbonate and quartz,and a molecular model of the asphalt was also constructed of the SARA content based on the twelve molecular model of the asphalt.Then,the aggregate-asphalt interface model was established with the constructed asphalt and mineral model,the influence mechanism of the interface hydrogen bonding,interface energy,and radial distribution function which reflected the interface relationship was studied.The results showed that:the hydrogen bonding of SBS polymer on the molecular model of the asphalt and mineral interface has different effects with different asphalt,mineral and different cleaved surface of the crystal.The asphalt-mineral interface system model can form hydrogen bonding under certain conditions.The addition of SBS polymer will affect the formation of the interface hydrogen bonding.The SBS polymer affects the interfacial energy and aggregation behavior of the interface system between asphalt and minerals.The interfacial energy of the system after adding the SBS polymer is lower than that of the interfacial system without the addition of SBS,and the interfacial energy does not change significantly with increasing temperature The asphalt-mineral interface system is less sensitive to temperature effects.The radial distribution function of the mineral model in the interface system after adding SBS polymer is not significantly different from the system without adding SBS polymer,and the range of the first peak of the asphalt radial distribution function curve is narrowed.The distribution of asphalt molecules is more concentrated.