A critical assessment of stiffness modulus and fatigue performance of plant produced asphalt concrete samples using various test methods

This project tested eight commonly used mixtures in Switzerland: three surface courses, three binder courses and two base courses. Three types of test methods for stiffness modulus EN 12697–26 and fatigue resistance EN 12697-24 were used: Namely, four Point Bending with prismatic sample (4PB-PR), Indirect Tensile test on cylindrical samples with pulse load form (IT-CY) and cyclic load form (CIT-CY). A total of 303 prismatic and cylindrical samples were prepared and tested. It was shown that the test procedures do not deliver the same results, both in terms of value and ranking. This is on the one hand due to the loading mechanisms and on the other due to the type testing parameters of temperature and frequency defined in the European standards. Regarding stiffness, the trend and ranking of the materials for two of the three methods (4PB-PR and CIT-CY) are similar for a majority of tested mixtures, regardless of the temperatures and frequencies used. IT-CY tests performed on eight mixtures did not show sensitivity to the mixture type as much as the 4PB-PR and CIT-CY tests that use a sinusoidal continuous force application. The fatigue resistance data show that the ranking of the two types of tests (4PB-PR and CIT-CY) for the eight mixtures tested was not the same. 4PB-PR tests induce bending and therefore are a more realistic indication of fatigue induced in the samples.