The introduction of modified asphalt binders provided transportation agencies an effective tool to design balanced mixtures that can resist conflicting distresses while maintaining good long-term durability. While conventional polymer modified asphalt mixtures have shown improved long-term performance, it is also believed that asphalt mixtures with high polymer (HP) content may offer additional advantages in flexible pavements subjected to heavy and/or slow moving traffic loads. While no unique and detailed handy guide that discusses the HP modification of binders and mixtures exists at this time, and while asphalt industry is moving towards the use of much more durable materials for a better long-term performance of newly constructed roads, this manuscript summarizes the findings from the literature review on the performance of HP asphalt binders and mixtures. The reviewed laboratory studies indicated that the increase in polymer content continues to improve the performance properties of binders and mixtures. The reviewed field projects showed encouraging early field performance without exhibiting any construction related issues. In addition, this article presents attempts that were explored to estimate a structural coefficient of HP mixes based on the available information from literature. This analysis led to the conclusion that the designed HP mixtures may lead up to 40% reduction in the asphalt layer thickness resulting in considerable upfront cost-savings.

Increased quantities of asphalt-based recycled materials can be incorporated in asphalt paving mixtures by using recycling agents. Previous studies demonstrated that restoring the required performance grade (PG) by the inclusion of recycling agents may not be sufficient to guarantee long-term durability. In this study the crossover temperature was used to characterise the viscoelastic properties of asphalt binders at the intermediate service temperature range for asphalt pavements. Durability thresholds for crossover temperature with aging were proposed on a trial basis from a correlation to the Glover–Rowe parameter. In combination with high PG, crossover temperature was used to evaluate rheological balance: resistance to early rutting and long-term embrittlement. Practical recommendations are provided in terms of appropriate materials selection (base binder, recycled, binders, and recycling agents) towards engineering long-lasting rejuvenated binder blends with increased quantities of recycled materials. Limitations and additional considerations for extending the rheological balance approach to evaluate polymer-modified materials are also summarised.

An investigation of the existence of predominant frequency, fp (or frequencies), and the ability to predict critical pavement responses in asphalt layers using those predominant frequencies has been presented. The study used an extensive database of computed pavement response histories of four different asphalt pavement structures (thin and thick) at two temperatures (21 and 40°C) subjected to a tandem axle load at three speeds (16, 65, and 97 km/h) using the pavement response analysis program 3D-Move Analysis. The conversion of load duration to frequency and the validity of using one response component (σzz) alone in the estimation of the pulse time (tp) were explored. Instead of focusing on only σzz, attention is given to all pavement response components (stresses and strains). In addition, verification of whether the use of a consistent set of fp value(s) can in fact adequately capture all components of pavement response has also been undertaken. The viscoelastic properties that are representa...

This paper summarizes the literature review as well as the documented use and performance of airfield pavements that used reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA). A review of in-service airfield pavements with RAP-containing HMA mixes was conducted as part of this study. Two civilian airports and one military airport were identified as currently using RAP in the HMA surface course. The three airports are Logan International Airport (BOS), Griffin-Spalding County Airport (6A2), and Oceana Naval Air Station (NTU). Furthermore, the impact of RAP on the performance life of HMA airfield pavements on a large hub, small hub, and general aviation was evaluated using actual airport traffic mixes. The performance life analysis used the characteristics and mechanical properties of HMA mixes in the linear elastic airfield pavement design software (LEDFAA1.3) to compare the estimated performance life of HMA pavements with and without RAP materials. The documented research effort has recently been con...

A compressive model for predicting thermal cracking events in asphalt pavements that accounts for the continuous evolution of the asphalt mixture properties with oxidative ageing over time has been developed. The model also considers temperature-dependent coefficient of thermal contraction (CTC) for the calculation of thermal strain in the asphalt layer. An improved pavement temperature profile estimate has been employed in the model to predict the required hourly pavement temperature data. The temperature data at the desired depth in the asphalt layer are then used in a kinetic-based ageing model to predict growth in the carbonyl (CA) of the asphalt binder over time. Using a refined one-dimensional constitutive linear viscoelastic relationship, the hourly thermal stress is then computed considering the changes in the viscoelastic and thermal contraction properties of the asphalt mixture with the increase in CA of asphalt binder used in the mix. The required age-dependent relaxation modulus is obtained from the dynamic modulus (E^*) of asphalt mixtures (i.e. in complex domain) at various ageing levels. Also, the required age and temperature-dependent CTC is obtained from thermal strain measurements of varied aged asphalt mixtures using the uniaxial thermal stress and strain test (UTSST). The cracking events are detected over the service life by comparing the predicted thermal stress with the age-dependent crack initiation stress (CIS) of the asphalt mixture. The age-dependent CIS is obtained from the UTSST results for different ageing periods. Preliminary analysis of the model revealed the accuracy of the model in a realistic prediction of the accumulative thermal cracking events for the asphalt pavement with different air void levels (4, 7 and 11%) and with unmodified (PG64-22) and polymer-modified (PG64-28) asphalt binders in a selected location.

The objective of this study was to assess the impact of aging on high polymer (HP)-modified asphalt binders when compared with conventional polymer-modified asphalt (PMA) binders on the basis of rheology- and chemistry-based parameters. An extended asphalt binder aging experiment that considered multiple combinations of PMA and HP binders from different sources was conducted. Long-term oven-aged asphalt binders at multiple temperatures and durations and asphalt binders aged in a pressure aging vessel (PAV) for multiple durations were tested using the dynamic shear rheometer. Several parameters were determined including low shear viscosity and Glover-Rowe parameters at various temperatures. The PAV-aged asphalt binders were further evaluated in terms of critical low temperature difference using the bending beam rheometer. All PMA and HP combinations were evaluated using Fourier transform infrared spectroscopy for characterization of chemical composition and assessment of polymer degradation. Overall, the measures indicated reduced susceptibility to aging of HP binders when compared with PMA binders, shown by a flatter slope with respect to oxidation with the low shear viscosity measures and Glover-Rowe parameters. In addition, the potential of polymer degradation for HP binders when compared with PMA binders was minimal with aging, thus indicating an increased longevity from a chemical-characteristic standpoint.