Assessment of mechanical tests for stiffness modulus determination of bituminous mixture

During the last decades the laboratory mechanical characterization of asphalt concretes has evolved thanks to the evelopment of innovative testing methodologies and equipments like those for the assessment of stiffness modulus. Those pieces of equipments enable the user to obtain the mechanical parameters of asphalts needed for the road avement structures rational and mechanistic design. The European Standard EN12697 part 26 ‘Stiffness’ has been ecently harmonized in Italy by UNI. This standard describes some of the available methods for the laboratory ssessment of asphalt stiffness, defining each test procedure as well as the calculations needed to obtain the mentioned arameters. In this paper two different methodologies have been adopted and compared performing tests on a single bituminous mix; indirect tensile tests (IT-CY) and four point flexural tests 4PB-PR) are the most common configurations for stiffness assessment, even though several set-up variables are ossible. After the stiffness appraisal and the comparison of the tests by means of the EN13108 specifications, the ethod nd timing of production of specimens as well as those needed to set up and to perform the test have been considered.