The economic benefits from use of RAP materials can provide a great boost to the highway industry by freeing funds for additional highway construction, rehabilitation, preservation, and maintenance. In recent years, the incentive to recycle has grown stronger because of concerns about the environment and sustainability. The general public is becoming more aware of the need to conserve natural resources through recycling. The use of RAP can result in sustainable development and cost savings by reducing the amount of virgin materials required in the production of the new asphalt mixture (1).Benefits notwithstanding, excessive amounts of RAP in a mixture can have detrimental effects on pavement performance. Xiao et al. reported that inclusion of 15% RAP resulted in a significant increase in stiffness of the mixture (2). In recent years, as asphalt prices have continued to escalate, a great deal of interest has been focused on the use of higher contents of RAP. Currently, RAP use varies considerably across the United States, but the average RAP content in asphalt mixtures is estimated to be around 15% (3).The belief that pavements constructed with RAP materials are more prone to cracking than virgin mixtures is generally attributed to stiffening and embrittlement effects induced by attempting to combine weathered, age-hardened materials with virgin materials. A careful RAP mixture design achieves proper binder stiffness by considering the aged binder stiffness, virgin binder stiffness, and the proportions of these two binder components present in the final blend. Extensive research has been directed toward characterization of low-temperature properties of pavements that contain RAP (1).The current study explores the effect of RAP amounts on the lowtemperature fracture properties of asphalt mixtures. Study of the lowtemperature fracture properties of HMA with RAP was conducted in the context of five RAP levels and two virgin binder sources. RAP levels of 10%, 20%, 30%, 40%, and 50% were studied with PG 64-22 and PG 58-28 virgin binders. Disk-shaped compact tension [DC(T)] fracture testing was conducted to determine the fracture energy of the mixtures. In addition to the DC(T) test, the Superpave ® indirect tensile (IDT) test, which is widely used in the prediction of low-temperature performance of asphalt mixtures, was conducted on HMA specimens that contained 20% and 40% RAP.A new testing method that was developed on the basis of the acoustic emissions (AE) phenomenon was employed to evaluate the low-temperature behavior of mixtures. The AE phenomenon refers to the generation of a transient, elastic mechanical wave caused by the sudden release of local stresses (strain energy) in a solid medium. When a material is mechanically or thermally stressed to the point Significant increases in the cost of asphalt paving and increased awareness of the need for sustainable infrastructure in recent years have in turn increased the use of recycled asphalt pavement (RAP) in the manufacture of hot-mix asphalt (HMA). The use of RAP...

No abstract

The use of recycled asphalt (RA) materials in pavement rehabilitation processes is continuously increasing as recycling techniques, such as cold recycling (CR), are being utilised in increasing magnitude and greater awareness for use of recycled materials and consideration of sustainable practices is becoming common in the construction industry. The focus of this paper is on developing a state of the art and state of the practice summary of processes used for classification of RA as well as the curing and specimen preparation practices for cold-recycled asphalt mixtures. A variety of topics were explored through an exhaustive literature search, these include RA production methods, definition of RA materials, stockpiling practices, industrial operations, specimen curing and preparation practices and in-field evaluation of cold-recycled rehabilitation. This paper was developed through efforts of CR task group (TG6) of RILEM Technical Committee on Testing and Characterization of Sustainable Innovative Bituminous Materials and System

No abstract

No abstract