Effect of Confinement Pressure on the Nonlinear--Viscoelastic Response of Asphalt Concrete at High Temperatures

摘要

Asphalt concrete materials exhibit the nonlinear viscoelastic responses at high stress/strainlevels. The traffic loading induces multi-axial stress states within the asphalt concrete pavementstructure. Therefore, it is imperative to characterize the nonlinear viscoelastic responses ofasphalt concrete under the realistic stress states since these nonlinearities significantly affect therutting and fatigue damage performance of pavements. Schapery’s (1) nonlinear viscoelasticmodel has been used extensively by several researchers to characterize the nonlinearity ofasphalt concrete materials. However, the available methods for characterizing the viscoelasticnonlinearity are mostly based on the simple uniaxial creep-recovery tests.In this paper, the nonlinear viscoelastic properties of asphalt concrete materials arecharacterized considering the effects of confinement pressure on the variation of the nonlinearparameters. Dynamic modulus test is used to obtain the linear viscoelastic properties and thetime-temperature shift factors. Cyclic creep-recovery tests are performed at high temperature(55°C) and at different confinement levels to characterize the nonlinear viscoelastic responses.The effect of confinement pressure is investigated through usage of triaxiality ratio on thevariation of the nonlinear viscoelastic parameters. The analyses showed that the triaxiality ratiohas substantial effect on the nonlinear strain response of the asphalt concrete. The significance ofthese nonlinear parameters on the complex response of asphalt concrete subjected to differentloading conditions is also discussed.