Effect of Blending Degree between Virgin and Aged Binder on Pavement Performance of Recycled Asphalt Mixture with High RAP Content

Ying Xu,Yunze Li,Jie Ji,Zhijing Chou,Shi-Fa Xu

doi:10.1155/2019/5741642

Abstract

In this study, the influence of the blending degree between virgin and aged binder on the pavement performance of hot-mix recycled asphalt mixture (HMRAM) with high RAP content is analyzed. The aggregate gradation of AC-16 was selected. The RAP contents were 30, 40, and 50%. HMRAMs with different degrees of blending (DOBs) were prepared by changing the mixing temperature (150, 165, and 180°C) without the occurrence of excessive aging for asphalt binders. An improved Hirsch dynamic modulus prediction model was then used to quantitatively characterize the DOB of HMRAM. Finally, the high-temperature, low-temperature, moisture stability, and fatigue resistance performance of HMRAM were tested and the effect of the DOB between the virgin and aged asphalt binder on the pavement performance was analyzed. The results showed that the DOB between the virgin and aged asphalt binder cannot reach 100% at the three mixing temperatures for HMRAM with 30, 40, and 50% RAP contents, which is inconsistent with the assumption of complete blending in China’s specification. The dynamic stability of the mixture gradually decreases with the increased DOB for HMRAM with a high RAP content, while the moisture stability, low-temperature, and fatigue resistance performance are continuously improved. This means that with the increase in DOB in the stage of open to traffic, meeting high-temperature performance criteria at the design stage may become unsatisfactory for HMRAM. The moisture stability, low-temperature performance, and fatigue resistance performances of HMRAM measured at the design stage were reasonable and conservative. The change in DOB significantly affects the content and properties of total free binder in HMRAM, affecting pavement performance. The content and physical properties of the RAP aggregate also have a significant impact on pavement performance.

Highlights

More transportation agencies are moving toward the increased use of reclaimed asphalt pavement (RAP) due to the increasing demand for environment-friendly paving mixtures and the significant increase in the costs of raw asphalt binder [1]
For hotmix recycled asphalt mixture (HMRAM) with a high RAP content (>30%), only the partial aged binders in the RAP are blended with the virgin binders, which results in inconsistency with the design assumption. erefore, the degrees of blending (DOB) quantification between the RAP binder and virgin binder is the key issue for the design of HMRAM with a high RAP content
Low-temperature performance, and fatigue performance of HMRAM meets the requirements of specification at the design stage, there is no risk that these pavement performances of HMRAM will decrease with an increase in DOB after construction

Summary

Introduction

More transportation agencies are moving toward the increased use of reclaimed asphalt pavement (RAP) due to the increasing demand for environment-friendly paving mixtures and the significant increase in the costs of raw asphalt binder [1]. In the production and mixing process of the hotmix recycled asphalt mixture (HMRAM), the aged binder coated outside the old aggregate in the RAP will be blended with a rejuvenator and virgin binder. Based on the mobilized proportion of the RAP binder, the degrees of blending (DOB) between the RAP binder and virgin binder are classified into no-blending (“black rock”), partial blending, and complete blending states [2]. HMRAMs are mostly designed based on the assumption of a complete blending state. For HMRAM with a high RAP content (>30%), only the partial aged binders in the RAP are blended with the virgin binders, which results in inconsistency with the design assumption. Erefore, the DOB quantification between the RAP binder and virgin binder is the key issue for the design of HMRAM with a high RAP content For HMRAM with a high RAP content (>30%), only the partial aged binders in the RAP are blended with the virgin binders, which results in inconsistency with the design assumption. erefore, the DOB quantification between the RAP binder and virgin binder is the key issue for the design of HMRAM with a high RAP content

Objectives

Methods

Results

Conclusion