Triaxial Deformation Behavior of Bituminous Mixes

Abstract

The triaxial compressive response of bituminous mixes with volume fractions of aggregate in the range 52 to 85% was investigated over a wide range stresses and strain rates. The types of loadings considered include triaxial monotonic constant stress and constant applied strain rate, as well as creep recovery, continuous cyclic, and stress pulse train loadings. The mixes with a “fully dense” aggregate skeleton were found to dilate under all loading conditions and the creep response of the mixes was dependent on both the deviatoric and hydrostatic stresses. By contrast, recovery was found to occur under zero applied deviatoric stresses with the recovery rate only dependent on the “recoverable strain” and independent of any superimposed hydrostatic stress. Continuous and pulse loading cyclic stress-controlled tests showed that the response of the mixes was governed by the mean applied deviatoric stress in the continuous cyclic tests while strain recovery was important in the pulse loading tests. A phenomenological constitutive model was proposed to fit the measured triaxial response of the bituminous mixes and shown to capture the measurements over all the triaxial stress states and loading time histories investigated here. Furthermore, the model was extended to capture the temperature dependence of the mixtures which is governed by the temperature dependence of the bitumen binder.