ABSTRACT
ABSTRACT: An extensive Round Robin Test (RRT) was conducted in Belgium in the course of 2007, mainly to evaluate the reproducibility of the new performance-related tests for polymer-modified binders (DSR, BBR, EVT2). As heterogeneity of test samples might be related to polymer modification, pure road bitumen was included in the analysis as a reference. In addition, two polymer-modified binders were chosen, one of which was sampled from a tank with a so-called “high-shear mixer”; this type of mixer is deemed to ensure better homogeneity of the binder. In order to minimize the differences induced by sample preparation, additional instructions were sent to the participating laboratories, complementing the specifications in the relevant standard EN 12594 for sample preparation. Although the RRT was intended for the new tests for PmBs, conventional tests such as needle penetration and Ring & Ball softening point were included in the test program as well. This allowed drawing conclusions at a later stage as to whether a possible dispersion in the test results is due to differences between laboratory samples or inherent to the test itself. This paper presents the statistical analysis of the results and draws conclusions on the reproducibility of the test results among Belgian laboratories. The results from the RRT are compared to precision data from other sources (including the test standards themselves), where available. In addition, the detailed data on sample preparation and test conditions are analyzed in order to establish any relationships with deviating results. This RRT, therefore, makes a contribution to both the knowledge and the validation of the new European tests for bituminous binders, especially polymer-modified binders.
