Behaviour of asphalt concrete mixtures under tri-axial compression

The mechanical behaviour of asphalt concrete is highly dependent on traffic loadings and environment conditions. Its compressive strength is sensitive to strain rate, temperature, as well as confining pressure. The influence of the confining pressure becomes more significant during the summer season due to the decrease of the viscosity of the bituminous binder which makes that the asphalt material tends to react more like an unbound granular material. This paper presents the results of an investigation into the effect of strain rate, temperature and confinement as determined on two different asphalt mixtures being dense and porous asphalt concrete. The results showed that the compressive strength and stiffness increased with a decreasing temperature, an increasing loading rate, and increasing confinement. The failure strength results of DAC in the I1-J2 space show a nonlinear failure envelope while the results of PAC show properties similar to frictional granular material. The investigation has shown that the critical failure envelope of DAC highly depends on the strain rate which is hardly the case for PAC.