FATIGUE BEHAVIOR OF ASPHALT MIXES: INFLUENCE OF LABORATORY TEST PROCEDURES ON FATIGUE PERFORMANCES

Since 1990, the LCPC carried out three "semi-scale" experiments on its test track aimed at studying the fatigue behavior of asphalt mixes in the aspect of the influence of the nature of asphalt. The large amount of laboratory tests carried out on the six different tested materials show that, if the modulus is a value relatively independent of the measurement method, the fatigue behavior in the laboratory strongly depends on the test procedure (frequency, temperature, two or three points bending, controlled force or displacement, with or without rest period). The results obtained don't allow to choose one type of fatigue test as more relevant than another one in all cases. A systematic study carried out in laboratory in order to better define the data obtained from the fatigue tests highlights the energy dissipated in the form of heat during the continuous tests. It also points out that the differences in the results between the continuous and discontinuous tests are probably not attributable to an actual healing of the material during the rest periods.