Influence of temperature and aging on laboratory fatigue performance of asphalt mixtures

This paper presents a laboratory study into fatigue characteristics of bituminous mixtures using the indirect tensile test. Three different asphalt concrete dense binder course materials were used in the study. These include an AC 20 designed with a 40/60 pen bitumen and two AC 14 designed with a 10/20 pen bitumen and a polymer modified binder, respectively. Controlled stress fatigue tests were carried out at two temperatures, namely 20 and 10 degrees C, on both unaged and aged cylindrical specimens. As the stiffness values of the materials were significantly high, reduced specimen thicknesses of 25 mm were employed to generate the required horizontal stresses. These specimens were obtained by sawing in half 50 mm thick specimens cored from roller compacted slabs. Furthermore, comparisons were made between the stiffness values of the core specimens and their respective halves. As regards fatigue performance, it was found that as the temperature decreased the fatigue life of the AC 20 material decreased, whereas those of the AC 14s, increased. Aged materials also showed shorter lives than the unaged ones but this reduction was more severe for the AC 20 mixture.