3D complex modulus tests on bituminous mixture with sinusoidal loadings in tension and/or compression

This paper presents an investigation into 3D viscoelastic behaviour of bituminous mixture. Complex modulus tests were performed at ENTPE laboratory on cylindrical samples, for three different modes of sinusoidal loading: only tension, only compression and tension–compression. Stress-controlled mode was used for cyclic tension tests and cyclic compression tests whereas cyclic tension–compression tests were conducted in strain-controlled mode. For all loading conditions, the strain amplitude of sinusoidal cyclic loadings is less than 60 µm/m. Complex modulus E * and complex Poisson’s ratio ν * were measured at five temperatures ranging from 1 to 30 °C and at six frequencies ranging from 0.03 to 10 Hz. The results indicated that complex moduli are the same for the three modes of loading for average and low temperatures. Rather small differences were obtained between complex modulus values obtained from the three types of loading for higher temperatures. These differences could be explained by nonlinearity (modulus value depending on strain level) and accumulated strain existing for only tension and only compression type tests. No noticeable differences in complex Poisson’s ratio could be obtained from the three modes of loading.