Estudo de misturas asfálticas com o Dynamic Shear Test para determinação do Flow Number Shear.

Abstract

Rutting of the surface of flexible pavements can be defined as the accumulation of longitudinal depressions that increase with repeated loading from vehicular traffic. It is a common distress in asphalt surface layers, whether due to problems related to the asphalt mixture, such as low shear strength and high thermal susceptibility, or due to densification and localized ruptures in the underlying layers and/or subgrade. The development of this distress can be avoided by selecting proper materials, advancing the design process of the asphalt mixtures, by satisfactorily compacting the mixes and elaborating a suitable pavement project with strict quality control in the execution. This work assesses the methodology of a test to evaluate the shear strength of the asphalt mixtures, in order to contribute to the development of the studies to prevent rutting. The dispositive was developed by the LEP/UFCG in partnership with the company JBR Engenharia, and patented along this research. The dispositive works interconnected to the UTM-25 press, manufactured by the IPC Global, which is software-programmed to control the load, the loading form, frequency, total deformation, number of cycles, test temperature and to identify the Flow Number Shear (FNShear) from the Deformation vs. Number of Cycles curve. To achieve the objective of this research, the Dynamic Shear Test was performed with asphalt mixtures composed of two different asphalt binders: an asphalt binder 50/70 and a polymer-modified asphalt binder 55/75. In addition, all the test samples were tested at five reference temperatures established for the execution of the tests, which were 35, 40, 50 and 60 °C. At the end, the obtained results were analysed in view of the different conditions imposed. It was possible to note the different levels of shear resistance of the asphalt mixtures and to obtain advances in the study of the mechanical behaviour of asphalt pavements, in particular against rutting appearance.