Classification and design of bituminous mixtures based on the variation of their strength and toughness with temperature: Fenix stress-strain diagram

The trend in road construction is to establish specifications based on functional and structural performance of the pavement layers. This trend gives construction companies more freedom to design and improve their products, which is a boost for innovation and efficiency in the design and construction of road networks in different countries. In order to make progress in this way, it is important to establish parameters that allow showing the quality of the materials and layers built and, above all, detect failures in the case of using inappropriate material or poor execution. In the case of bituminous mixtures, it is necessary to start from the properties that characterize this material, mainly provided by the bitumen. The bitumen agglomerates the aggregates giving resistant and ductile unions. That is, we must control the strength of the mixture, but especially its flexibility and ductility. When the mixture loses these properties with the passage of time due to aging of the binder, rapid cracking and failure of the bituminous mixture occurs. This article includes the application of a specially designed test to measure the ductility and strength of bituminous mixtures subjected to tensile stresses, Fenix Test. In essence, the Fenix Test is an asymmetric tensile test that induces a slow and controlled crack propagation, something that does not occur in the existing tests that are used to measure mixture’s tensile strength. In addition, the test can be conducted at different temperatures, which allows to obtain the curve that characterizes the mixture in a stress-strain diagram. Such curve shows the response of a mixture in a wide range of temperatures, indicating whether the response is brittle or ductile, lower in strength or tough.