Authors: Joerg Patzak & Frohmut Wellner
The mechanistic design of asphalt pavements is based upon the scientific knowledge in engineering mechanics and material technologies of both, asphalt and unbound structural layers. The deformation behaviour of the unbound granular materials (UGM) used in structural pavement layers is very complex due to their inherit nonlinear stress dependency and the effect of bulk material factors, such as water content, density, grain size distribution, etc. Thermal effects plays an important role on the mechanical deformation of UGM when the following two conditions are met: (1) water is present and (2) the temperature fluctuates in the saturation range (i.e. changes from positive to negative °C, or vice versa). Due to extreme climatic conditions, these freeze and thaw cycles are very common in most of the granular base layers of flexible pavements in central European countries. In this context, this paper presents selected results of an investigation about the effect of the temperature on the mechanical deformation of UGM under cyclic triaxial conditions using the results of Repeated Load Triaxial (RLT) tests with Variable Confining Pressure (VCP).
Keywords: mechanical deformation behaviour of UGM, pavement design, pavement construction, cyclic testing, temperature influence, stress depending material behaviour, freezing and thawing during cyclic testing, phase transition of water in UGM, Young´s modulus, Poisson's ratio