Research on blending and diffusion phenomena of virgin and aged asphalt during the laboratory-simulated construction stage

Abstract

This research aims to quantify the degree of blending (DoB) between virgin and aged asphalt binders in recycled asphalt mixture during construction stage by using the Confocal Laser Scanning Microscopy (CLSM) technology. In this research, virgin SBS-modified binder was employed as a tracer. Wood cube aggregate was used as RAP aggregate to be distinguished from the asphalt mixtures. Various heating temperature and storage time conditions were set up for laboratory-produced recycled asphalt mixtures to simulate different construction stages, including storage, transportation, laying, and compaction processes. The CLSM was utilized to detect fluorescence concentration diffusion of virgin SBS-modified binder on the simulated RAP aggregate samples at each construction stage. A method for quantifying the DoB of virgin and aged asphalt binders was proposed. Results demonstrated that the simulated construction stages have significant impacts on blending efficiency of virgin and aged asphalt binders. After mixing process, the DoB of tested binders was found to be 43.4 %. The DoB values increased 19.7–31.6 % during storage stage range, and 7.2–9.2 % during transport stage. The DoB values only increased 2–4 % during laying and compaction stage. The overall increase of the DoB can be as high as 30 %, indicating that settings of construction stages are crucial for the blending of virgin and aged asphalt binders in recycled asphalt mixtures.