Development of blending model for RAP and virgin asphalt in recycled asphalt mixtures via a micron-Fe3O4 tracer

Abstract

The blending efficiency of the aged and virgin asphalt profoundly determines the performance of the recycled asphalt mixtures. While the elimination of disturbances caused by observation means and the quantification of the blending degree of blended asphalt deserve further investigation. This paper developed the blending model for reclaimed asphalt pavement (RAP) and virgin asphalt by virtue of micron-Fe3O4 tracer. The properties of Fe3O4 tracer and its impact on virgin asphalt were determined. And the effect and contribution of various factors on blending degree were explored by Fourier Transform Infrared Spectroscopy (FTIR) based on orthogonal design and multiple linear regressions method. The results indicate that micron-Fe3O4 tracer with irregular flake structure and unique absorption peak of a Fe–O bond endows its desirable tracing effect. Involving Fe3O4 tracer in virgin asphalt elevates its high temperature rheological properties without serious harmful influence on flow properties and cracking resistance. Blending temperature and blending time demonstrate the significant influence on blending degree, compared to unapparent action of RAP content. Blending time reveals highest range and smallest statistical significance, followed by blending temperature and preheating temperature of RAP, resulting in its largest influence on blending degree. Appropriate extension of blending time is recommended for greater blending degree and superior performance of recycled asphalt mixtures. The blending model and comprehensive fitting equation are conducted to predict the blending degree and provide guidance for designing recycled asphalt mixtures.