Study on the Effect of Microwave Processing on Asphalt-Rubber.

Jing Xu,Yongkang Li,Rui Li,Tao Liu,Jianzhong Pei,Qinghui Luo

doi:10.3390/ma13020411

Jing Xu, Yongkang Li + Show 4 more

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https://doi.org/10.3390/ma13020411

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Abstract

The addition of crumb rubber (CR) into base asphalt plays a critical role in the improvement of the performance of Asphalt-Rubber (AR) binders. However, due to the problems, like high constructing temperature and energy consumption brought by the additional rubber, the use of AR binders could be limited in some areas. During this study, CR is processed by microwave is adopted to reduce the viscosity of the AR binders system, while the CR processed by long screw extrusion also is studied. First, the swelling (the absorption of light component into the CR particle) and dissolution (some molecules of CR dissolving into the base asphalt), both of which determine the improved performance of AR binders, are investigated by fluorescence microscopy and extraction tests. The size of the CR particle after swelling observed by fluorescence microscopy is used to evaluate the swelling rate of CR samples, and the ratio of the weight loss of CR samples after extraction to the original weight is employed to measure the dissolution rate. Then, Brookfield rotational viscometer and storage stability tests are conducted. Last, the rheologic performance, including high and low-temperature performances, is characterized by the dynamic shear rheometer (DSR) and bending beam rheometer (BBR), respectively. The fluorescence microscopy and extraction results show that microwave processing could effectively increase the swelling and dissolving rate, with the figures rising twofold and more than threefold, respectively. The results show that microwave processing could effectively reduce the viscosity of AR binders, with a viscosity decrease of 65% at 190 °C and, at the same time, the high temperature of Performance Grade (PG) decrease from 88 °C to 76 °C. The storage stability could be negatively impacted, but it is slight and the low-temperature performance is improved slightly.

Highlights

Asphalt Rubber (AR) generally refers to the mixture containing crumb rubber (CR), which is obtained by grinding the recycled crumbs of tires with base asphalt [1]
The volume of CR particles after the same swelling time and under the same experimental process was adopted during this study to evaluate the swelling rate of different types of CR
A fluorescence microscope at the mode of magnification of 200× was used to observe the samples, and the single swelling particle in the observation area was chosen to calculate the volume of particles

Summary

Introduction

Asphalt Rubber (AR) generally refers to the mixture containing crumb rubber (CR), which is obtained by grinding the recycled crumbs of tires with base asphalt [1]. The improvement of the performance of the AR binders is thought to be mainly coming from the adding of CR [10,11]. This improvement lies in two key effects that the CR brings about: the particle effect (PE) and interaction effect (IE) between CR and asphalt [12].

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