Analysis of viscosity and composition properties for crumb rubber modified asphalt
Introduction
The rubber with excellent property is extensively adopted in industry, transportation, medicine and in other fields, and accordingly the waste of resources and environmental contamination turn out to be increased arising from the waste rubber. How to harness waste rubber and protect the environment has raises the problem to be urgently resolved. The harnessing of waste rubber as a modifier, adding to the asphalt to prepare RA has aroused the extensive concern from the domestic and foreign road workers [1], [2], [3]. The crumb rubber in the hot asphalt can optimize the property of asphalt through the swelling, degradation and a series of complex physico-chemical processes [4]. Viscosity is perceived as an important indicator for the evaluation of rubber asphalt property, its variations evidently manifest the rheological properties differences of RA. Abdelrahman [4] started the swelling and degradation behaviors of crumb rubber in RA. Li [5] anatomized the physico-chemical behaviors of crumb rubber in the modified asphalt. Hoang [6] made the viscosity model of material parameters of the polymer. Putman [7], Rui [8], Lougheed [9], Shi [10] studied the viscosity characteristics of RA in different aspects, and thereupon a lot of research results on RA viscosity has made by the impacts exerted by rubber dosage, rubber size, prepared temperature of RA, reaction time and other factors [5], [6], [7], [11]. However, these factors almost were qualitative analysis, the viscosity characteristics and mechanism of action still are required to be delved into.
In this study, RA were prepared in the case of different conditions of mixing temperature and processing time for different rubber dosage and rubber size. The viscosity of RA in the case of different preparation conditions shall be tested, and thereupon the viscosity characteristics and influencing factors shall be anatomized. RTFOT aging test of RA shall be conducted, and the visco-flow activation energy () of RA was acquired through adopting Arrhenius equation in line with the viscosity values of RA in the case of different temperatures, and the visco-flow characteristics of RA were anatomized. The viscosity definition is made based on the contribution of base asphalt (BE), rubber and asphalt interaction effect (IE) and crumb rubber particle effect (PE). To isolate the PE, the sieving test was designed. Rotary viscosity tests were conducted on RA samples and asphalt samples separated from crumb rubber through adopting Brookfield viscosity meter. The impact exerted by these factors on the viscosity composition parameters IE and PE of RA was anatomized, and the viscosity prediction model of RA was established.
Section snippets
Materials
A typical virgin asphalt binder was adopted. Its properties were tested and listed in Table 1. A kind of commercially available 20, 40, 60, 80-mesh crumb rubber from the Changda Huachu company was adopted in this investigation. The appearance is black. The physical and chemical parameters are listed in Table 2.
Rubber asphalt(RA) preparation
To ascertain the viscosity and Composition for rubber asphalt, RA were prepared in the case of the different conditions through heating and stirring. Preparation conditions are listed in
Impact exerted by crumb rubber content on the viscosity of RA
The crumb rubber dosage is an important influencing factor for the property of RA. Guo [11] studied to show that the property of RA is better when the range of the rubber dosage is 18%–24%; the resistance crack property on low temperature of RA is good when the range of the rubber dosage is 5% to 20%. RA was made with 0%, 5%, 10%, 15%, 20% and 25% the crumb rubber of the virgin asphalt binder weight (the crumb rubber size is 60 mesh) , in the 90 min treatment time, different treatment
Analysis of visco-flow characteristics of rubber asphalt
In order to study the visco-flow characteristics of different types of rubber asphalt in the case of different temperatures, the rubber asphalt prepared in the case of the conditions of treatment temperature 180 °C and treatment time 90 min and its RTFOT samples tested rotational viscosity by through adopting different rubber content, and the test temperatures: 135 °C, 160 °C, 170 °C and 180 °C. The viscosity of the different content of RA and aged RA in the case of different four temperatures
Relationship between the dosage of crumb rubber and viscosity composition parameters
The dosage of crumb rubber is an important factor for the viscosity of rubber asphalt. In general, the greater the dosage of crumb rubber, the higher the viscosity of rubber asphalt, the better the high temperature property, but the excessive dosage of crumb rubber may result in the fatigue of rubber asphalt and the lack of low temperature property. Guo [11] studied that the property of rubber asphalt is better when the range of the rubber dosage is 18% to 24%; the rubber asphalt has a good
Rubber asphalt viscosity prediction model
In line with the foregoing analysis, it can be attained that the rubber dosage, rubber size, mixing temperature, treatment time are the influencing factors that affect the viscosity of rubber asphalt, in which the impact exerted by rubber dosage is the most significant. For the rubber asphalt samples prepared through adopting the same type and size crumb rubber, the IE values show linear relation with the dosage of crumb rubber, while PE values increase by the exponential growth model
Conclusions
The viscosity values of RA increase by the exponential growth model continuously with the increase of rubber content. There is a certain equivalence for rubber asphalt viscosity between raising mixing temperature and extending the processing time. But too high temperature or excessive time may result in excessive degradation of rubber molecules, which shall cause the decrease of RA viscosity.
With the increase in the dosage of crumb rubber, Eη of RA for origin or aged samples both goes up first
Acknowledgments
This work was supported by Natural Science Basic Research Plan in Shaanxi Province of China (2017JM5099), the Special Fund for Basic Scientific Research of Central Colleges (310821162010 & 310821163404), and the National Natural Science Foundation of China (51768062). The authors gratefully acknowledge their financial support.
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