Performance-Based Asphalt Mix and Pavement Design

Prediction and optimization of in-service performance of road pavements during their live time is one of the main objectives of pavement research these days. For flexible pavements the key performance characteristics are fatigue and low-temperature, as well as permanent deformation behavior at elevated temperatures. The problem facing pavement designers is the need to fully characterize the complex thermo-rheological properties of hot mix asphalt (HMA) over a wide temperature range on the one hand, while on the other also providing a realistic simulation of the traffic- and climate-induced stresses to which pavements are exposed over their design lives of 20 to 30 years. Where heavily trafficked roads are concerned, there is therefore an urgent need for more comprehensive test methods combined with better numerical forecast procedures to improve the economics and extend the service lives of flexible pavements under repair and maintenance programs.

This papers therefore focus on performance-based test methods on the basis of existing European standards that address effective mechanical characteristics of bituminous materials and which may be introduced into national requirements within the framework of European HMA specifications. These test methods comprise low temperature tests, i.e. the tensile stress restrained specimen test or the uniaxial tensile strength test, stiffness and fatigue tests, i.e. the four point bending beam test or the uniaxial tension compression test, as well as methods to determine permanent deformation behavior by means of dynamic triaxial tests.

These tests are used for the performance-based mix design and subsequently implemented in numerical pavement models for a reliable prediction of in-service performance, which, in combination with performance-based tests, enables a simulation of load-induced stresses and mechanogenic effects on the road structure and thus improved forecasts of the in-service performance of flexible pavements over their entire service lives.