New Generation Mix-Designs: Laboratory-Field Testing and Modifications to Texas HMA Mix-Design Procedures.

摘要

Recent changes to the Texas hot mix asphalt (HMA) mix-design procedures such as adaption of the higher-stiffer PG 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: (1) comparative evaluation of the Texas gyratory and balanced mix design (BMD) methods; (2) development and evaluation of numerous HMA mix-designs including RAP and RAS mixes, (3) extensive laboratory test including Hamburg rutting and Overlay Tester crack evaluations; (4) accelerated pavement testing and performance evaluation; (5) 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.