Factors Affecting Variability in Strategic Highway Research Program Binder Tests

Two binder technician workshops were held in January 1998, one at the Connecticut Advanced Pavement Laboratory at the University of Connecticut and one at the Northeast Center of Excellence for Paving Technology at Pennsylvania State University. These workshops were followed by a second set in 1999. The overall objective was to improve the repeatability of the test methods used to grade Superpave® asphalt binders. During the workshops, participants demonstrated and discussed the techniques used in their own laboratories. A document, Manual of Practice for Testing Asphalt Binders in Accordance with the Superpave PG Grading System, was developed for use by asphalt binder technicians and as a training aid for a proposed binder technician certification program. The results of the discussions that were held during the workshops and the items that are presented in the manual of practice are summarized. The results were grouped into four main categories: (a) handling, sampling, and sample preparation; (b) temperature measurements; (c) equipment calibration; and (d) testing procedures. The items discussed here and in the manual of practice supplement and clarify the current AASHTO test methods. The test methods in themselves are not sufficient to ensure uniformity in testing practice from one laboratory to the other.