A major result of the research conducted under the Strategic Highway Research Program from 1987 to 1993 was the development of the Superpave (Superior Performing Asphalt Pavement) system for the comprehensive design of asphalt pavements. These 14 contributions describe the experience to date in the

The Strategic Highway Research Program (SHRP) was a highly focused, ambitious research effort that targeted four specific areas for intense study over the time frame from 1987 to 1993. Asphalt was one of the four study areas. This report describes the Superpave system, the final product of the asphalt research program; and the various parts that comprise its operational characteristics. In all, the final report of the SHRP Asphalt Research Program consists of five parts, the contents of which are briefly described in this report. Reference is made within this report to specific details within the other four parts for readers who want a more detailed description of the methodology, test methods, and theory behind Superpave.

The Superior Performing Asphalt Pavement (Superpave) mix design system was developed under the Strategic Highway Research Program, which was completed in 1993. Superpave consists of new methodologies for evaluation and selection of hot mix asphalt (HMA) material constituents along with new laboratory compaction protocols. During Superpave development, significant research focused on the performance grade asphalt binder system and gyratory compaction development. In contrast, very little research was performed to determine those aggregate properties and specification requirements most closely related to HMA mix performance. In 2000, the aggregate industry prepared a white paper for, and at the request of, the Transportation Research Board Expert Task Group on Superpave Mixtures and Aggregates. The paper focused on discussion of aggregate related issues that presented challenges to the implementation and use of Superpave. Since the white paper was written, Superpave has undergone modifications (specifications and general use or practice) based on completed research and general knowledge obtained. Many Superpave modifications were addressed in varying degrees in the white paper, and it is now important to discuss the impact of these modifications on HMA performance and the aggregate industry. In addition, other aggregate related issues are presented and discussed, including inconsistent fine aggregate definition, influence of minus 0.075 mm sieve material on fine aggregate specific gravity determination, aggregate production and particle shape, and the influence of aggregate on dynamic modulus.

The primary objective of this full-scale accelerated pavement testing was to evaluate the performance of unmodified and polymer modified asphalt binders and to recommend improved specification tests over existing SUperior PERforming Asphalt PAVEment (Superpave) binder performance grading methodologies. Candidate replacement tests were evaluated via their ability to discern fatigue cracking resistance and rutting. Two fatigue cracking specification tests were identified as more capable in capturing performance than others: binder yield energy and critical tip opening displacement. Two rutting specification tests that quantify irrecoverable deformations exhibited the best strength to capture rutting: multiple stress creep and recovery and oscillatory-based nonrecoverable stiffness. Based on the full-scale performance and laboratory tests, crumb rubber (recycled tires) modified asphalt (Arizona wet process) was shown to significantly slow or stop the growth of fatigue cracks in a composite asphalt pavement structure. A hybrid technique to modify asphalt with a combination of crumb rubber and conventional polymers (terminally blended) exhibited good fatigue cracking resistance relative to the control binder. Also, a simple addition of polyester fibers to asphalt mix was shown to have high resistance to fatigue cracking without the use of polymer modification. The research study also quantified the capabilities of the National Cooperative Highway Research Program's mechanistic-empirical pavement design and analysis methodologies to predict rutting and fatigue cracking of modified asphalts that were not captured in the calibration data from the Long-Term Pavement Performance program. Falling weight deflectometer, multidepth deflectometer, and strain gauge instrumentation were used to measure pavement response. The results illustrated that the nationally calibrated mechanistic-empirical performance models could differentiate between structural asphalt thickness but had difficulty differentiating modified from unmodified asphalt binder performance. Nonetheless, the mechanistic-empirical performance ranking and predictions were enhanced and improved using mixture-specific performance tests currently being implemented using the asphalt mixture performance tester.

The global response to COVID-19 has demonstrated the importance of vigilance and preparedness for infectious diseases, particularly influenza. There is a need for more effective influenza vaccines and modern manufacturing technologies that are adaptable and scalable to meet demand during a pandemic. The rapid development of COVID-19 vaccines has demonstrated what is possible with extensive data sharing, researchers who have the necessary resources and novel technologies to conduct and apply their research, rolling review by regulators, and public-private partnerships. As demonstrated throughout the response to COVID-19, the process of research and development of novel vaccines can be significantly optimized when stakeholders are provided with the resources and technologies needed to support their response. Vaccine Research and Development to Advance Pandemic and Seasonal Influenza Preparedness and Response focuses on how to leverage the knowledge gained from the COVID-19 pandemic to optimize vaccine research and development (R&D) to support the prevention and control of seasonal and pandemic influenza. The committee's findings address four dimensions of vaccine R&D: (1) basic and translational science, (2) clinical science, (3) manufacturing science, and (4) regulatory science.