QUEIROZ, R. F. R.; http://lattes.cnpq.br/0797354567525193; QUEIROZ, Rita Flávia Régis.
Resumo:
One of the main asphalt pavements mechanisms of degradation is the fatigue cracking. This defect is characterized
by the initiation, expansion, and connection of microcracks, with a high degree of localization and non-linear
characteristics (CHEN et al., 2021). The formation and propagation of cracks in the asphalt mixtures, in general,
occurs due to the repeated loads applied by the vehicles, generating tensile stresses, also associated with aging
and temperature. In more critical situations, this process leads to structural failure of the asphalt mixtures. In recent
years, the use of direct tensile fatigue tests associated with the simplified viscoelastic continuous damage model
(S-VECD) has been shown to be an effective tool for evaluating fatigue in asphalt materials. This model uses
fundamental material properties to characterize the asphalt mix performance from an efficient and simplified
laboratory test protocol. This study aims to evaluate the fatigue damage of asphalt mixtures modified by the addition
of polymer from the results of the direct tensile fatigue test with the application of the S-VECD model. Three asphalt
mixtures were produced with the same granulometry (maximum nominal size of 19mm and designed by the
SUPERPAVE methodology), varying only the binder. Three asphalt binders were selected to compose this
research: a) CAP 50/70 as base binder for comparison; b) AMP 55/75, a commercial product prepared with the
addition of SBS and c) CAP 50/70 modified by the combination of EMA-GMA+HDPE+PPA. The binders were
evaluated for physical and rheological properties (Performance Grade - PG and MSCR), and fatigue using the
Linear Amplitude Sweep - LAS test, using the S-VECD model. The asphalt mixtures were evaluated for stiffness
using the tensile strength (RT) and resilience modulus tests (MR), to permanent deformation from the uniaxial
repeated load test (Flow Number), the LVE behavior was characterized based on the dynamic modulus test, and
fatigue performance was evaluated from the uniaxial direct tensile test with application of the viscoelastic damage
model S-VECD.The results of the LAS test indicated that the modified CAP 50/70 presented the best fatigue
performance, being classified according to the FFL as excellent. The mixtures with modified binders presented the
highest values of RT and MR, indicating greater rigidity in relation to the mixture with the base binder. Regarding
permanent deformation, from the Flow Number parameter, mixtures with modified binders are classified for heavy
traffic, which is consistent with the MSCR result in which the AMP 55/75 and modified CAP 50/70 binders are
indicated for heavy traffic with based on the Jnr parameter. As for the LVE behavior, the mixture with modified CAP
50/70 showed the expected behavior, with higher dynamic modulus values at high temperatures (low frequencies),
and the lowest modulus values at lower temperatures (high reduced frequencies). Furthermore, for the entire
spectrum of frequencies and temperatures, the mixtures with modified CAP 50/70 presented the lowest phase
angle values, indicating a more elastic and less viscous behavior. From the direct traction test, based on the failure
criterion Gr
, the asphalt mixture with modified CAP 50/70 showed better fatigue performance, with a higher FFM
value and following the same trend as the FFL. Based on the ܦ
Dr
failure criterion, from the damage capacity ܵSapp
the mixtures with modified CAP 50/70 and AMP 55/75 were classified as having the best fatigue performance.
Therefore, the use of binders modified by addition of polymers promoted asphalt mixtures with better fatigue
damage performance.