Influence of temperature on the fatigue life of flexible pavements

Abstract

Flexible road pavements are the solution usually implemented in Portugal for the construction of highways. The properties of the bituminous mixtures used in this type of pavement are greatly influenced by environmental temperature, mainly due to its effect on the bitumen viscosity. The main aim of this work is to evaluate the performance of bituminous mixtures in pavements, at different temperatures, in relation to two of their fundamental properties, namely stiffness modulus and fatigue cracking resistance. These properties control the behaviour of recently developed thin surface layers, since they do not show significant permanent deformation. Some bituminous mixtures, such as Asphalt Concrete (AC 0/14), Stone Mastic Asphalt (SMA 0/12), Asphalt Rubber (AR 0/10) and Porous Asphalt (PA 0/14), used in surface layers and overlays, were selected for experimental characterization, The stiffness moduli of those mixtures were determined at the temperatures of 5, 15 and 25 ºC. The AC 0/14 was selected for further testing in order to assess the fatigue life at the temperatures of 5, 15 and 25 ºC. The influence of temperature on the stiffness modulus and on the fatigue life of the bituminous mixtures is empirically considered in Shell fatigue life equation normally used in the pavement design. A comparative analysis between the pavement design results achieved by using Shell fatigue life and those obtained from laboratory tests performed on the AC 0/14 at different temperatures was carried out. The main conclusions of this work are related to the different evolution of stiffness moduli and fatigue life regarding different temperatures, temperature influence on the total design thickness of bituminous pavement layers and whether the Shell fatigue life equation is the most adequate for Portuguese materials and in-service conditions.