Analysis of unbalanced binder oxidation level in recycled asphalt mixture using GPC

In a conventional hot-mix asphalt recycling process, the reclaimed asphalt pavement (RAP), generally, is mixed with the virgin binder and aggregates and, sometimes, recycling agent. During this process, all materials are mixed for a short time period, the aged binder in the RAP is expected to be melting off from the old aggregate and rejuvenated by virgin binder. To evaluate whether or not the RAP binder is well rejuvenated, gel-permeation chromatography (GPC) test was performed for the binders located on virgin and RAP aggregate particles separately in a recycled mixture. Large molecular size (LMS) of each binder was evaluated and absolute viscosity of the binder was estimated based on the LMS data. It was found that there was a significant difference between LMS levels of the binders coating RAP and virgin aggregates in the same recycled mixture. This discrepancy is a shortcoming of the conventional recycling method, which should be corrected by some technique for producing better quality recycled materials.