Linear Viscoelastic Properties of Bituminous Materials: from Binders to Mastics (With Discussion)

Mastic, composed of bitumen and filler, is an intermediate material between bitumen and mix. It plays the true role of binder in the mix. An experimental campaign has been performed at the ENTPE/DGCB laboratory in order to measure the linear viscoelastic properties (at low strain level) of mastics with a specifically developed experimental device (annular shear rheometer). The effects of the filler characteristics (type, size, concentration, gradation) and aging of the binder on the complex shear modulus (G*) of mastics have been analyzed on a large range of temperatures (from -25°C to 80°C) and frequencies (0.03 Hz to 10 Hz). A significant change in behavior between bitumen and mastics with high filler content (> 40% vol.) is observed and quantified. The new reinforcement complex coefficient RA *, introduced in this paper, allows to show that the filler effect is important at high temperature and/or low frequency. The filler gradation (size and spread of grains size values) seems to have little influence on the viscoelastic properties of mastics. In addition, the effect of binder aging on the mastic behavior is quantified by the aging complex coefficient. It seems not to be influenced by the filler type and the filler gradation. A rheological model (2S2P1D) developed at the ENTPE/DGCB laboratory is used to simulate the experimental results for all the materials. Correlations between the constants of the model and constituents of the materials are underlined.