Caracterização à fadiga de misturas asfálticas por compressão diametral e comparação com os resultados do ensaio de tração-compressão

Abstract

The study of fatigue performance of asphalt mixtures is of great importance to prevent this distress in road pavements, whose need is highlighted in the current context of Brazilian paving, which begins the implementation of an empirical-mechanistic approach to pavement design, denominated National Dimensioning Method (MeDiNa). The fatigue characterization of the asphalt materials adopted by the new method is carried out from the indirect traction test which, despite having certain limitations, is widely accepted in Brazil. As a result, the present research characterized the fatigue behavior, through indirect traction test, of 9 asphalt mixtures, 6 of them collected during the construction of road segments monitored by UFSM and 3 dosed and mixed in laboratory, with conventional binder and rubber asphalt. The test results indicated, in general, a satisfactory fatigue behavior of the materials studied. The parameters obtained during the fatigue characterization of the asphalt mixtures collected from the monitored road sections were used in representative simulations of the 5 segments of Santa Maria in MeDiNa 1.1.5, aiming to estimate the percentage of cracked area in the surface asphalt layer based on the experimental data that, when compared with the respective results obtained in the field surveys, showed that the MeDiNa analysis correctly described the progression of the fatigue phenomenon observed in the respective segments. In order to compare the fatigue performance of the asphalt mixtures, simulations were carried out, with the same structural and loading conditions, varying the thickness and the asphalt material used in the surface layer, in MeDiNa 1.1.5 and Layered Viscoelastic Pavement Analysis for Critical Distresses (LVECD) 1.1 software, which is based on the fatigue characterization through the direct tension fatigue test and the S-VECD model, determined in previous researches. With these simulations, the materials were ranked according to the percentage of predicted cracked area, highlighting the divergences and similarities pointed out by these tools analysis, since the MeDiNa simulations indicate the superiority of the asphalt mixture with conventional CAP from UFSM 1 test section, while the LVECD analysis indicate the best performances for the mixtures with rubber asphalt. Once the fatigue characterization of the same asphalt mixtures was available both by the indirect traction test and the direct tension test, a procedure was sought to predict the indirect traction test fatigue curves using the direct tension test data. Through an iterative process, displacement coefficients were obtained that translated the experimental direct tension test Wöhler curves to be closer to the respective indirect traction test curves. When comparing the predicted fatigue life values and those actually obtained in the test, it was observed that the proposed procedure was, in general, satisfactory, especially on lower levels of deformation.