Evaluation of asphalt fatigue properties in the laboratory

Three-point flexural fatigue tests have been carried out on prismatic specimens cut from laboratory manufactured slabs of five asphaltic materials including a hot rolled asphalt, a dense bitumen macadam and a stone mastic asphalt. Identical slabs of these materials were made to produce cylindrical specimens which were tested in the diametral fatigue test, called in the UK the indirect tensile fatigue test (ITFT). A detailed derivation is presented of the theory used to establish the feasibility of the ITFT as a fatigue test for asphaltic materials. The test results show that, at low strain levels, the fatigue lines of the five mixtures from the ITFT assume similar relative positions to those from flexural tests. However, for the same strain level, the fatigue lives measured in the ITFT are considerably shorter for all the mixtures tested. The paper highlights some of the concerns observed in connection with the ITFT procedure and their implications for fatigue testing practice.