A COMPARISON OF FIELD AND LABORATORY ENVIRONMENTS ON ASPHALT DURABILITY

After many years of asphalt durability studies using field test sections to evaluate different asphalts under various conditions, which failed to provide consistent data due to many uncontrolled variables, the California Transportation Laboratory attempted a different approach in which most of the variables and constants could be controlled. This asphalt durability study involved the weathering of carefully controlled and fabricated briquettes in 4 distinctly different field environments for 4 years. The aim of the study was to compare effects of various field environments on asphalts in briquettes to the effects produced on the same asphalts by various lab accelerated weathering procedures. The controlled variables included 3 different asphalts representing high, high moderate, and low temperature susceptibilities; 3 void ranges, 3-5%, 7-9%, and 10-12% voids; and 2 aggregate sources representing absorbent and nonabsorbent characteristics. All briquettes were weathered in identical trays at each weathering site. In addition, a correlating test road was later studied that used one of the study asphalts in a desert site in the vicinity of the briquette desert weathering site. Complete details regarding the design, fabrication, and installation of the briquettes can be found in an initial report for this project.