Precision of Test Methods for Hot Mix Asphalt

The paper presents the Portuguese experience in the precision evaluation of test methods for hot mix asphalt (AC 14 surf and AC 20 base). The repeatability and reproducibility values were determined based on Proficiency Test Schemes involving several laboratories. The tests were performed from 2007 until 2021. The paper analyses the soluble binder content, maximum density (Method A), bulk density (Procedure B), and Marshall properties (stability and flow). The results were compared with the European standards’ precision data. The analysis confirmed a wide variation of the precision data. Precision was not always constant, but, in some cases, it did seem to be influenced by the characteristics of the bituminous mixture, contrary to the variation presented in the test standards. In general, a lower reproducibility was observed.