Effects of Recycled Asphalt Pavement Amounts on Low-Temperature Cracking Performance of Asphalt Mixtures Using Acoustic Emissions

Abstract

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...

Effect of temperature and air void on mixed mode fracture toughness of modified asphalt mixtures

“…The single edge notched bend beam (SENB) subjected to three or four-point bend loading [1,12,15,42,43], the modified indirect tension (IDT) specimen [11], the disc shape compact tension (DCT) specimen [13,14,18,44], the center cracked diametral compression disc (Brazilian disc) specimen [45] and the semi-circular bend (SCB) specimen subjected to three-point bend loading [3,6,10,16,19,23,46-54] are some of the previously used test configurations for investigating the crack growth behavior of asphalt mixtures. It should be noted that many of the mentioned specimen, cannot provide pure or dominantly mode II loading cases.…”

“…Since 1970, a large number of research works have been performed to study the fracture resistance of different asphalt mixtures using the concept of fracture energy or the stress intensity factor by employing numerical analyses, simulation techniques and experimental methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The influence of asphalt characteristic specifications including the binder type, aggregate type, size of aggregates, air void contents, temperature, and loading condition have been investigated in the past for different asphalt mixtures.…”

Evaluation of Low-Temperature Cracking Performance of Asphalt Pavements Using Acoustic Emission: A Review

“…The "transition region" The embrittlement temperature represents the onset of thermal damage in the asphalt concrete test sample. It is hypothesized that the embrittlement temperature represents a fundamental material property that is independent of material constraints, sample size (as long as a statistically representative volume or larger is used), and sample shape [3,32,33,38,39]. The "transition region" can be considered as the region where material behavior gradually changes from a quasi-brittle to a brittle state in which resistance to fracture is generally very low, allowing cracks to propagate readily.…”

A Review of Warm Mix Asphalt Technology: Technical, Eco-nomical and Enviromental Aspects

“…In mixtures modified with rubber and RAPs, the aim of using WMA technology is to improve workability during their manufacturing and compaction processes, rejuvenate and soften the aged asphalt binder of the RAP, and create new construction methods with high environmental and economic benefits (Zhao et al 2013). Nonetheless, most researchers report that high contents of RAP produce mixtures that are so stiff that structural failure can occur in the field, mainly fatigue cracking (Bonaquist 2005;McDaniel et al 2007;Behnia et al 2011;Doyle and Howard 2013;Mogawer et al 2013). This is mainly due to the increase in stiffness that is a product of the asphalt aging in the RAP.…”