This study evaluated sensitivity of the repeated simple shear test at constant height (RSST-CH) based on laboratory rutting (permanent deformation) characteristics of fine mixes used in WesTrack full scale testing in Nevada.
Mix variables in this study included three aggregate gradations, three asphalt contents, and three air void contents. For each mix, three replicate specimens were tested for a total of eighty-one specimens. The RSST-CH tests were performed according to AASHTO TP7 Procedure F. These tests were conducted at 50°C temperature for 10000 cycles or 5% plastic shear strain, whichever occurred first. The loading cycle consisted of 69-kPa haversine load with 0.1 second loading time followed by 0.6-second rest period.
The test results — permanent shear strain, and dynamic shear modulus evaluated using the RSST-CH test — were found to be sensitive to the mix parameters: aggregate gradation, asphalt content, and air void content. A statistical analysis of test results confirmed the above finding that the differences between permanent shear strain and dynamic shear modulus for various mixes were due to different gradation, asphalt content, and air void content and not due to RSST-CH test variability.