微观尺度下温拌再生混合料新-旧沥青界面融合特性

The extent of blending between virgin and aged binders plays a decisive role in the performance of recycled mixtures. Analyzing the diffusion process of virgin and aged binders and quantifying their mixing degree are of great practical significance for the design and performance adjustment of recycled mixtures. To simulate the diffusion behavior of virgin and aged binders, their interface fusion characteristics were explored: the quantitative fusion degree of virgin and aged binders under different mixing conditions and influence of compatible penetrant on the migration depth of virgin and aged asphalt. In this study, the three stages of virgin and aged binder fusion of warm mix recycled mixture were simulated at the microscopic scale: physical binding, mechanical mixing, and mutual diffusion; based on the stratified extraction, the molecular weight and distribution of bitumen were obtained by gel permeation chromatography (GPC), and the degree of fusion between the two kinds of asphalt was quantitatively analyzed. Then, suitable molecular tracers and test parameters were selected to study the migration depth of the virgin and aged binders using Fourier transform infrared spectroscopy (FTIR), and the influence of compatible penetrant on the migration depth of virgin and aged asphalt was discussed. The results show that the mixing efficiency defined by the macromolecular ratio (LMS) can effectively and quantitatively characterize the fusion of virgin and aged asphalt; the mixing efficiency of the virgin and aged asphalt in the warm mix recycled mixture was 29.8% in the non diffusion stage, and 56.3% after 2 h of heat preservation in the diffusion stage, with a difference of 26.5%. In the diffusion stage of the virgin-aged asphalt fusion, heat preservation is beneficial for improving the fusion of the virgin-aged asphalt. Amino-terminated butadiene acrylonitrile rubber (ATBN) can be used as a suitable molecular tracer because it has groups that asphalt does not have, and adding compatible penetrants with good permeability can increase the penetration depth of aged asphalt. When there are three extraction layers, without a compatible penetrant, the migration depth of the virgin and aged binder is two layers. After adding a compatible penetrant, the migration depth increased to three layers.