The current performance grade (PG) binder specification uses the parameter G*sin δ to quantify binder fatigue property, which has long been known to be the weakest part of the specification. The purpose of this study was to identify a better binder fatigue test. Six asphalt binders with a variety of modifiers were characterized using five asphalt binder tests, including the G*sin δ, elastic recovery test, the multiple stress creep recovery (MSCR) test, the linear amplitude sweep (LAS) test, and the double edge notch tension (DENT) test in this study. Additionally, the push-pull asphalt mix fatigue test was employed to verify these binder fatigue tests. Comparing the results of the binder tests and the asphalt mix push-pull test, this study further confirmed the poor performance of the parameter G*sin δ to differentiate binder fatigue resistance. It was also found that neither the MSCR nor the LAS test showed good correlation with asphalt mix fatigue resistance. Finally, it was identified that both...

Cracking has become a primary mode of distress in recent years that frequently drives the need for rehabilitation of asphalt pavements. Meanwhile, asphalt mix designs are becoming more and more complex with the increasing uses of recycled materials, recycling agents, binder additives/modifiers, and multiple warm mix asphalt technologies. Thus, there is an urgent need to identify reliable cracking tests that can be used for routine mix design to eliminate brittle mixes. This paper critically reviewed cracking mechanisms and laboratory tests. A total of 12 cracking tests were discussed at a cracking test workshop held as part of the National Cooperative Highway Research Program Project 9-57. Seven cracking tests were selected for further laboratory evaluation and field validation. Four of the simpler cracking tests from the seven were evaluated in this paper, these being the Texas Overlay Test (OT), Disk-shaped Compact Tension (DCT) test, Semi-Circular Bend test from the Louisiana Transportation Research Center (SCB-LTRC), and SCB test at room temperature from Illinois (SCB-IL). A laboratory sensitivity study was performed, and the results showed that all four cracking tests were generally sensitive to asphalt mix components. However, there were some concerns with the DCT, SCB-LTRC, and SCB-IL. Both the DCT and SCB-IL were found to be not sensitive to asphalt binder content; and both the DCT and SCB-LTRC showed an unexpected increase in cracking resistance when adding RAS to the mix. Additionally, two sets of field test sections were used for preliminary validation of these four cracking tests. It was found that the OT, DCT, and SCB-IL provided rankings which matched the measured field performance for the two sections on US62, Texas; and the OT and SCB-LTRC were valid for six APT test sections. Further validation with different mixes, traffic, and climate is needed.

The purpose of this paper is to present a new mechanistic-empirical (M-E) rutting model developed for hot-mix asphalt (HMA) overlay thickness design and analysis. After reviewing existing rutting models in the literature, it was found that the well-known VESYS layer rutting model still is a rational choice and was adopted with minor modification to model HMA overlay rutting development. The main feature of the proposed M-E HMA overlay rutting model is to characterize layer specific permanent deformation properties rather than global rutting parameters used in the Mechanistic-Empirical Pavement Design Guide. For each specific layer, the proposed model requires rutting parameters α and μ ; and these rutting parameters, which are two of the fundamental input parameters required in the proposed M-E rutting model, can be directly determined from the repeated load test following the test protocol discussed in the paper. Additionally, the proposed M-E HMA overlay rutting model was calibrated using 8 test section...

The purpose of this paper is to present a new mechanistic-empirical (ME) reflective cracking model developed for hot-mix asphalt (HMA) overlay thickness design and analysis. After reviewing existing models, the reflective cracking model based on Paris’ law of fracture mechanics was considered as the state of the practice and was selected as the basis for the ME model development in this study. The model consists of stress intensity factor and fracture properties ( A and n ) as the fundamental input parameters for modeling reflective crack propagation caused by both traffic loadings (bending and shearing) and thermal effects (temperature variations). For practical application, 32 SIF regression equations were developed for HMA overlays with three levels of load transfer efficiencies (10, 50, and 90%) at joints/cracks under various traffic loading spectrums (bending and shearing) based on more than 1.6 million finite element simulations and computations. For the thermal induced reflective cracking, a “hybri...

Under the same applied traffic loading, time is traditionally assumed to be a function of only the vehicle speed and the depth beneath the pavement surface. Additionally, no definite loading waveform has been established and/or recommended for any one special loading situation. After numerous computations and analyses in this study, it was found that the loading time is not only a function of the vehicle speed and the depth beneath the pavement surface but is also a function of the moduli ratio between the layer of interest and the immediate succeeding layer below. Furthermore, the loading waveform changed with depth beneath the pavement surface and the moduli ratio. Based on the results of this study, new equations for more accurately determining the loading time were proposed. Additionally, the corresponding loading waveform, which is a function of the depth beneath the pavement surface and the moduli ratio, was recommended. Plausible results were also obtained when an iterated method was introduced to ...

Extensive laboratory tests were conducted and the results were compared to the known field performance results of Specific Pavement Studies-1 (SPS-1) sections on US281. The objective was to establish which of the available laboratory test procedures could match the observed field performance. The laboratory tests included the diametral resilient modulus, Asphalt Pavement Analyzer (APA), Hamburg Wheel Tracking Test (HWTT), Repeated Simple Shear Test at Constant Height (RSST-CH), dynamic modulus test, and repeated load permanent deformation test. It was found that both RSST-CH and repeated load permanent deformation test could differentiate the performance of different sections, and the results matched closely with the field performance. The total permanent strain was also found to be a reasonable indicator of field rutting performance. For the wheel tracking tests, the APA performed better than HWTT, but both failed to differentiate some mixes. The moduli at high temperature, including dynamic modulus, axial resilient modulus, shear resilient modulus, and E*/sin δ could screen out the bad mixes. However, those moduli (except for shear resilient modulus) failed to further differentiate the performance of mixes once they were grouped as generally “good” or “bad”.