Estudo da resistência ao cisalhamento de misturas asfálticas a partir de ensaios com aplicação de cargas repetidas com o pórtico modular (Dynamic Shear Procedure/Lep)

Abstract

As the main types of pavement failure are low-temperature cracking, fatigue cracking and permanent deformation, we can infer that studies searching for solving or at least reducing those pavement defects are strongly contributive for the improvement of pavement design. Permanent deformation is characterized by the longitudinal depression in the wheel path and is mainly related to the road traffic intensity, temperature conditions, type of asphalt, mix design, etc. Analyzing a bunch of permanent deformation evaluation tests, some of the most important are static creep test, dynamic creep test and leutner shear test. In that regard, this work intends to contribute, based on previous tests of permanent deformation, introducing a new method for evaluation of those defects by using a new equipment, the Pórtico Modular, developed by the Laboratory of Pavement Engineering (LEP). In this equipment, samples of asphalt mixtures are subjected to dynamic shear loads. The above mentioned procedure is based on the dynamic creep test. An important parameter from this test, which is responsible for designate the test, is the Flow Shear Number, which is the number of cycle corresponding to the application of a dynamic load parallel to the shear plane of the specimen, where the deformation cannot be recovered anymore. The Flow Shear Number, point where deformation rate reaches the minimum, can be obtained from the largest real root of the second derivative of the deformation against the number of cycles curve. The function that better fit the points from the Flow Shear Number test was reached in this study by the curve fitting method. For the performed tests, the function that fits better with the deformation against number of cycles curve was the fifth degree polynomial. Another test performed in this study was the leutner shear test, which is different from the initial setup only because of the use of the modular and multitest portico developed by LEP, which brings great versatility and economy of steel in the manufacturing process. The maximum shear force, which is statically applied to the specimen at the same direction of the Flow Shear Number test, is obtained in this test. Presented results show that the new equipment can be used in the Leutner shear test without any losses.