Comparison of the two point bending and four point bending test methods for aged asphalt concrete field samples

Complex modulus and fatigue behavior are important characteristics for all materials. Some European countries have developed performance oriented requirements for bituminous mixtures. Using such requirements it is expected that the life of pavements can be improved. According to the European standards, these properties are characterized by various methods including two point bending (2PB) on trapezoidal specimen and four point bending (4PB) on prismatic specimen. It is known that the fatigue results obtained are highly dependent, in addition to the mixture variables and environmental variables, on specimen fabrication procedure and test equipment and procedure. Therefore the question remains how comparable are the results obtained from these tests? Up to date, a significant amount of data on comparison of the results of such tests is absent. This paper presents results of a Swiss inter-laboratory study on 2PB and 4PB tests for complex modulus and fatigue conducted on a wide pallet of specimen produced from aged field sections. The results show that a good linear regression for complex modulus values were obtained, however, the fatigue performance ranking obtained from the two tests were dissimilar.