Volume 2, Issue 3 (March 2005)
Field Validation of Superpave Shear Test on NCAT Test Track
When the National Center for Asphalt Technology Test Track was built in 2000, one of the primary objectives was to determine the ability of a number of laboratory tests to predict the permanent deformation of various mixtures. Repeated Shear at Constant Height (RSCH) was included as one of the tests in the laboratory study. The subject of this paper is field validation of the Superpave Shear Tester (SST) based on the field rutting data from the Test Track. Permanent shear strain, slope of the deformation rate, repetitions to a certain strain level, and shear modulus were the parameters evaluated for RSCH. The sensitivity of SST test to asphalt binder type in the various test track sections was analyzed. The relationship between RSCH test results and field rut depth was poor. This was partly due to the good quality of the track construction, thick pavement structure, and mild summers during the loading of the 2000 track, which did not cause any significant rutting. The sensitivity study indicated that PG 76-22 binder performed better than the PG 67-22 binder in the RSCH test. The criteria developed by the Asphalt Institute seem to be in a reasonable range.