Evaluation of aging behaviors of asphalt binders through different rheological indices

Rheological properties of asphalt binders modified with styrene-butadiene-styrene (SBS), ground tire rubber (GTR), or polyphosphoric acid (PPA)

It is well known that asphalt rheology affects the cracking performance of asphalt binders. For many years researchers have struggled to develop tests that adequately deal with this aspect of pavement performance in a manner that can be incorporated rapidly into a specification. The use of the fatigue parameter developed during the Strategic Highway Research Program (SHRP), G*sin δ, has been shown to be a poor surrogate for cracking performance. Other tests, such as the direct tension test, used for cold-temperature cracking, also have been implemented poorly into specifications. However, use of the bending beam rheometer as an indicator of cold-temperature cracking has been widely adopted. As a result, a pavement stiffness of 300 MPa has been regarded as a reasonable parameter for cold-temperature cracking performance. The interrelationship between cold-temperature cracking parameters and those selected for fatigue cracking is not well understood. The onset of brittle behavior that occurs around 300 MPa stiffness and the selection of a fatigue parameter G*sin δ at 5 MPa are not wildly divergent in concept. More recently, the Glover–Rowe parameter has been revealed as a good indicator of cracking performance. In this paper we explore those differences that have occurred and make suggestions for the use of alternate parameters to better define the rheology of the binder as it relates to cracking.

The Influence of Binder Rheology on the Cracking of Asphalt Mixes in Airport and Highway Projects

Use of recycling agents in asphalt mixtures with high recycled materials contents in the United States: A literature review

Improving fatigue and low temperature performance of 100% RAP mixtures using a soybean-derived rejuvenator

A laboratory study was conducted to evaluate if there was any potential relationship between asphalt binder properties and non-load related cracking, as part of a research project involving airfield asphalt pavements. The objective of the research was to identify one or more parameters that could be easily determined by testing that would allow an airport manager to monitor the loss of durability experienced with aging and to use the information to evaluate when the airfield asphalt pavement would need preventative maintenance to minimize the effects of non-load associated cracking. Three asphalt binders were selected representing different expected aging characteristics, in the laboratory study. Testing was conducted on asphalt binders in their unaged condition, as well as on asphalt binders that had undergone long-term aging in the Pressure Aging Vessel (PAV) at 100C and 2.1 MPa pressure for 20, 40, and 80 hours. The purpose of the longer PAV aging times was not to correlate with any expected service life, but simply to create a more highly-aged sample. Past research suggested some relationship between ductility (conducted at an intermediate temperature) and the durability of an asphalt pavement. Using ductility as the hypothesized property related to flexibility, two parameters were identified that related well to ductility and the expected loss of flexibility with aging. The first is a parameter suggested by other researchers—G′/(η′/G′)—as determined using the Dynamic Shear Rheometer (DSR). The second is a parameter that quantifies the difference in continuous grade temperature for stiffness and relaxation properties—referred to in the paper as ΔTc. In both cases, the parameters appear to quantify the loss of relaxation properties as an asphalt binder ages. Limited field testing from three general aviation airports generally confirmed the findings from the lab study, with the newer pavements having values of G′/(η′/G′) and ΔTc that displayed more flexibility and less aging than the older pavements. Based on the study results, values were determined for both parameters that could provide an indication of a loss of durability that could result in a greater risk of non-load associated cracking.

Evaluation of the Relationship between Asphalt Binder Properties and Non-Load Related Cracking

The main goal of this research was to help users determine the proper timing of preventive maintenance by identifying how environmental aging affects asphalt material properties (binder and/or mixture) in the pavement and how the application of pavement preservation treatments impact the aging process. Two main test sections were studied: (1) a designed experiment on the Low Volume Road portion of MnROAD to look at aging through the application of treatments on an annual basis over a five-year period; and (2) a 10-year-old pavement on TH 56 in southern Minnesota, also a designed experiment, with seals applied on an annual basis over a four-year period. Mix testing on TH 56 cores indicated that subsections with chip seals applied more than two years after construction had essentially the same fracture energy properties as the unsealed control subsection – implying that the initial treatment from a preservation standpoint should occur within the first two years of the pavement’s life to mitigate damage from environmental aging. The MnROAD sections did not show the same response. Based on the testing conducted during the study and the associated findings, it appears that rheological tests can be conducted on the asphalt binder recovered from a pavement core to assess the effects of oxidative aging. When possible, it appears prudent to use a mixture fracture energy test, such as the Disk-Shaped Compact Tension test, in conjunction with asphalt binder rheological testing to quantify the effects of aging within a pavement and suggest appropriate timing for the application of preservation treatments.

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Douglas I Hanson

Papers

Evaluation of the Relationship between Asphalt Binder Properties and Non-Load Related Cracking

Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in Hot-Mix Asphalt Pavements