Comparison of Asphalt Mixtures Crack Resistance at Intermediate Temperatures using Advanced Test Methods and Theories

Abstract

Due to the increased use of recycled materials in pavement, the crack resistance of asphalt mixtures has become a major concern. This study evaluated the crack resistance of asphalt mixtures containing up to 40% reclaimed asphalt pavement (RAP) at intermediate temperatures. Three groups of materials consisting of seven plant-produced hot-mix asphalt mixtures were evaluated. A suite of test methods with various mechanistic backgrounds were employed, namely: semi-circular bend, simplified viscoelastic continuum damage, indirect tension, Texas overlay, and Illinois flexibility index tests. The corresponding parameters obtained for assessing crack resistance were: critical strain energy release rate Jc, material fatigue sensitivity, dissipated creep strain energy, number of cycles to failure Nf,OT, the interaction plot of critical fracture energy versus crack progression rate, and the flexibility index, respectively. Test results indicated that mixtures with higher RAP content exhibited higher stiffness and indirect tensile strength with lower compliance than the counterpart materials. In addition, all evaluation parameters, except for the use of the interaction plot from the Texas overlay test, provided consistent observations that incorporation of more RAP deteriorated the materials’ crack resistance. The mixture-discriminating capabilities of all test methodologies were also investigated using the paired t-test on the experimental data of each mixture group. The results presented herein were part of Pooled Fund TPF-5(294) study titled Develop Mix Design and Analysis Procedures for Asphalt Mixtures Containing High-RAP and/or RAS Contents.

Investigation on self-healing of neat and polymer modified asphalt binders

“…Crack may initiate at the bottom of the asphalt layer due to tensile stress or beneath the tire due to shearing and propagate through the layer under repeated traffic loading. A number of test methods has been developed and implemented in the past decades for evaluating the fatigue resistance of asphalt concrete [1,2], including the well-known four-point bending beam fatigue test. Meanwhile, it has also been widely recognized that there exists a pronounced discrepancy between the laboratory and field measured fatigue lives.…”

Relationships among Chemistry, Rheology, and Fracture/Fatigue Performance of Recovered Asphalt Binders and Asphalt Mixtures Containing Reclaimed Asphalt Pavement

“…Table 1 presents the plant-produced asphalt mixture composition from three sources (1,2,3). It is noted that the three sources were obtained from states participating in the FHWA Transportation Pooled Fund Project TPF-5(294).…”

“…A common concern of RAP application in asphalt pavements is that the stiffness of the asphalt mixture increases as the amount of RAP content is increased ( 2–4 ). The stiffening effect is usually accompanied by embrittlement, which reduces the cracking resistance of asphalt mixtures ( 5, 6 ).…”

“…Laboratory studies have shown that incorporation of RAP improved asphalt mixture’s resistance to permanent deformation and moisture damage because of the presence of aged asphalt binder ( 2, 4 ). In relation to cracking performance, Cao et al ( 3 , 9 ) evaluated the effects of RAP, recycled asphalt shingle (RAS), and warm-mix technologies on the chemical and rheological characteristics of asphalt binders as well as the fatigue performance of asphalt mixtures using different testing methods. The report found that the inclusion of RAP reduced cracking resistance of hot-mix asphalt mixtures.…”