Assessment of cracking resistance of bituminous mixtures by means of Fenix test

Abstract

This paper shows the application of a new direct tensile test developed at the Road Research Laboratory of the Department of Transport and Regional Planning of the Technical University of Catalonia. The test is called Fénix test and is aimed at the assessment of cracking resistance of different types of bituminous mixtures at different temperatures. Fénix test calculates the dissipated energy during the cracking process of the material and the softening phase in the load-displacement curve of the test. The test procedure consists of subjecting one half of a 63.5 mm thick cylindrical specimen of a 101.6 mm diameter prepared by Marshall or gyratory compaction to a tensile stress at a constant displacement velocity (1 mm/min) and specific temperature. A 6 mm-deep notch is made in the middle of its flat side where two steel plates are fixed. The specimen is glued to the steel plates with a thixotropic adhesive mortar containing epoxy resins. Both plates are attached to a loading platen so that they can rotate about fixing points. Different types of mixtures with different stiffness moduli, including very flexible mixtures like gap-graded and SMA mixes, as well as stiffer mixtures like high modulus mixtures, were tested. The results were compared with those obtained for the same mixtures from standard fatigue bending beam tests.