| SBS modified asphalt as the main types of modified asphalt used in road highway engineering in our country, which is widely used in high-grade pavement construction due to its excellent performances. However, in the construction process of SBS modified asphalt mixture, the high temperature will cause a series of problems such as huge energy consumption, dust and gases that lead to environmental pollution. The use of warm mix asphalt(WMA) can effectively reduce the construction temperature of hot mix asphalt mixture, it is a kind of energy-saving and emission reduction green road building material, but the technical feature of reducing construction temperature makes its water stability a great challenge, and the microscopic mechanism of the adhesion of Warm mix asphalt and aggregate is not yet clear, which becomes a major bottleneck that restricts the popularization and application of this technology.In this paper, the adhesion of SBS modified asphalt under different raw material types and content is firstly studied. Calculate the asphalt cohesive work under different raw material parameters based on the method of Surface Free Energy, respectively considering five factors that are the type of matrix asphalt and SBS modifier, the content of SBS, compatible agent and stabilizer. At the same time, the influence of different raw material parameters on the nano-adhesion characteristics and microstructure of SBS modified asphalt was compared and analyzed, according to the result of AFM experiments, and the correlation of cohesion work and adhesion force were also analyzed. On this basis, study the microscopic mechanism of the influence of different raw material on the adhesion characteristics of SBS modified asphalt.Secondly, two kinds of different warm mix SBS modified asphalt of Sasobit and Evotherm were prepared, with the SBS modified asphalt as the original asphalt. Through the surface free energy theory and AFM technology, get the adhesion performance indexes such as cohesion work, adhesion work, stripping work, compatibility ratio and nano-adhesion force under wet and dry conditions, and combined with the results of AFM image scanning experiments, the influences of warm mix additives on SBS modified asphalt adhesion properties were explored.Finally, the adhesion characteristics of the control asphalt and warm mix SBS modified asphalt were evaluated both before and after aging by Surface Free Energy and nano-adhesion force, and compare the change of the asphalt topography and phase diagram before and after aging. At the same time, quantitatively evaluate the effects of aging on chemical structure of warm mix SBS modified asphalt, according to the change of absorption peak and functional group index in the infrared spectrum. On this basis, the correlation between the nano-adhesion force and different asphalt adhesion property index, Asphalt functional index is analyzed, so as to set up the internal relations between asphalt’s microstructure and chemical structure and adhesion performance under the condition of aging.The conclusions of this study are as follows:(1)There is a big difference between the adhesion work and the Nano-adhesion force of SBS modified asphalt under different matrix asphalt, and there is the compatibility problem exists in the adhesive property. The appropriate increasing of the SBS content is beneficial to improving the cohesion of SBS modified asphalt and its adhesion to aggregate, so that the resistance to water damage of asphalt-aggregate system is gradually strengthened. With the increase of the amount of extract oil, the cohesion work of SBS modified asphalt is firstly increases and then decreases. When the amount of extract oil is more than 3.5%, the cohesion work of SBS modified asphalt tend to decrease. With the increase of stabilizer content, both the adhesion work and the Nano-adhesion force of SBS modified asphalt increase, and the adhesion indexes showed good correlation.(2)The results of the test on the two aspects of cohesive and adhesive properties show that the water stability of asphalt mixture is enhanced when the warm mix agent of Evotherm is added, while the resistance of moisture damage of asphalt mixture is decreased by the addition of the warm mix agent of Sasobit. The Nano-adhesion force of asphalt sample after soaking is smaller than that before soaking, which shows that the water stability of asphalt mixture is reduced by soaking. Cohesion work, adhesion work and the compatibility rate have a certain positive correlation with the index of the Nano-adhesion force, and the correlation between adhesion and the Nano-adhesion force is the best. When compared with the condition of no soaking, the colloid structure of the asphalt surface after soaking tends to be changed from the "solution-gel type" to "the sol-type".(3)The Surface Free Energy and the Nano-adhesion force of the original asphalt and warm mix asphalt after aging were both decreased, but the extent of the decreased adhesion of the original asphalt is more than that of warm mix asphalts, from the viewpoint of the Nano-adhesion characteristics, the warm-mixed agent can improve the anti-aging properties of asphalt. The honeycomb structure and the continuous phase of asphalt after aging have the phenomenon of "merging", which shows the aggregation of asphalt in the process of aging. The result of FTIR test shows that the original asphalt and warm mix asphalt generate the oxidation reaction in the process of aging, and the SBS modifier also degrades. The decrease of the Nano-adhesion force of asphalt after aging is greatly related to the increase of the oxygen-containing functional groups that result from the oxygen oxidation reaction of asphalt in the process of aging, and experiencing less effect of the degradation of SBS when it is modified. |
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