Development Of Guidelines And Specifications For Use Of Wma Technology In Delivering Hma Products Inclusive Of Non Conventional Mixtures Such As Sma S And Mixtures With Rap And Ras Content

Development of Guidelines and Specifications for Use of WMA Technology in Delivering HMA Products Inclusive of Non-conventional Mixtures Such as SMA's, and Mixtures with RAP and RAS Content

Evaluation of the Moisture Susceptibility of WMA Technologies

"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's description

New Generation Mix-designs

Recent changes to the Texas hot mix asphalt (HMA) mix-design procedures such as adaption of the higher-stiffer performance grade asphalt-binder grades and the Hamburg test have ensured that the mixes that are routinely used on the Texas highways are not prone to rutting. However, performance concerns have been raised with these HMA mixes that are now drier, more difficult to compact, and more susceptible to premature cracking. This is particularly problematic with the dense-graded mixes (Type C and D) that are widely used throughout the state of Texas. Therefore, there has been a great need to either: (1) modify the existing Texas HMA mix-design criteria and/or to include new simpler cracking test procedures; or (2) develop new mix-design methods that will optimize HMA field performance, particularly with respect to cracking. As a means toward addressing these issues, this report provides documentation of a 4-year research study that included the following major tasks: a) comparative evaluation of the Texas gyratory and balanced mix design (BMD) methods; b) development and evaluation of numerous HMA mix designs including reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) mixes, c) extensive laboratory test including Hamburg rutting and Overlay Tester crack evaluations; d) accelerated pavement testing and performance evaluation; e) field testing and performance monitoring of in-service highway test sections. Based on the study findings and as documented herein, recommendations for updates and modifications to the Texas HMA mix-design methods were made. Additionally, new guidelines and specifications were also developed for new generation HMA mix-design procedures. Overall, the BMD method that is rutting-cracking performance based exhibited superiority over the traditional Texas gyratory mix-design method, particularly in terms of HMA mix constructability and cracking performance.