Physical properties of crumb rubber modified asphalt binders and environmental impact consideration

Abstract

The use of Crumb Rubber Modifier (CRM) with asphalt binders improves their properties by reducing their temperature susceptibility; depending on the way CRM and binder react with each other. The CRM particles tend to absorb some oils from asphalt binder and swell, resulting in a higher viscosity and thus stiffer binder. This paper discusses the effect of adding CRM to asphalt binder produced in Jordan by applying three different percentages of CRM on two asphalt binders, namely, Grade 60-70 and Grade 85-100. A total of 120 specimens were prepared to test their basic physical properties such as penetration, softening point, ductility, flash and fire points, and rotational viscosity. It was found that modified asphalt binders with higher crumb rubber content have lower ductility and penetration number, but higher softening point and viscosity values. Hence, this could be sign of rutting resistance and extended service life. Furthermore, different analytical methods were utilized to validate the experimental results. It was reported that only penetration displayed change in behavior for grade 60-70 and 85-100 asphalt binders. CRM content was found to be influential on all performance-related physical tests. Finally, the combined effect of asphalt-types and CRM content is statistically significant on softening point, ductility and rotational viscosity test results. On the other hand, the energy saving due to CRM incorporation coupled with other benefits including less cracking and maintenance makes rubberized asphalt very attractive and beneficial in highway construction. Rubberized asphalt technique reduced the environmental impact of highway construction by 5% to 10% compared to traditional practice.