Influence of Temperature on Asphalt Mixture Stiffness Modulus

It is well known that temperature has a great influence on performance of asphalt layers. Low temperatures raise the asphalt stiffness modulus which finally results in low temperature cracking. On the other hand, the increase of the temperature softens the asphalt binder and the stiffness modulus significantly drops. This, in combination with traffic load, causes asphalt pavement distresses like rutting, corrugation and shoving. In order to ensure reliability in asphalt pavement design, values of the design variables should, as much as possible, match the actual pavement performance conditions. As the asphalt stiffness modulus is one of the input parameters, it is important to know its values for temperatures that pavement will be subjected to during its life time. The temperature range in Croatia usually varies between -10°C and 40°C. According to the test method prescribed by European standard EN 12697-26 (Stiffness), Annex C (Test applying indirect tension to cylindrical specimens, IT-CY), stiffness was tested at four different temperatures, on several types of hot mixed asphalt mixtures. Based on the test results, temperature-stiffness correlations were obtained for the asphalt mixtures typically used in Croatia, for bearing or wearing courses. The application of the obtained stiffness modulus, as the parameter that describes the performance of asphalt layers under different temperature conditions, will enable the optimization of the existing pavement design method in Croatia.