Effect of Crumb Rubber Modifier (CRM) on Rutting and Fatigue Resistance Characteristics of Asphalt Binders



During the past few years major advancement in characterization of load-related damage resistance behavior of asphalt binders has been achieved. A new protocol for measuring resistance of binders to rutting and to fatigue damage has been introduced by the NCHRP 9-10 project and published in NCHRP report 459. In addition new protocols to measure construction relation properties, such as Zero Shear Viscosity for mixing and compaction and storage stability under static and high agitation conditions, are proposed.
This study was conducted to evaluate the effectiveness of a newly developed crumb rubber based technology on damage and construction related properties of asphalt binders commonly used in California. An AR4000 and an AR 8000 were used as the base asphalts and were modified with various types of chemically treated crumb rubber products that were introduced in asphalts as a dry product and allowed to react for a very short time (45 minutes) at selected temperatures.
The results show that Crumb Rubber Modifier (CRM) can be used at relatively low concentrations (5% by weight) to impart major improvements in binder characteristics without the need for long and sometimes costly digestion and blending times. They also show how these newly developed tests can capture the significant influence of these rubber technologies on damage characteristics and also construction related properties.
The paper also includes extensive testing for moisture damage and adhesion showing effect of CRM on moisture damage properties. The paper concludes with overall analysis showing importance of damage testing and effect of rubbers on asphalt quality.

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