Estudo do efeito deletério da água em misturas asfálticas a quente produzidas no Rio Grande do Sul

Abstract

Asphalt pavements should provide users with safe and reliable transportation, however, agents such as traffic actions, weather conditions and inadequate maintenance result in the process of road deterioration. The water is a propellant that is coupled to this problem, being able to change the distribution of stresses, the damaging properties and the stiffness parameters, changing the strain / deformation relationship and all the mechanical behavior of the asphalt mixtures. Thus, studies that address the influence of humidity on the aspects of stiffness and damage of asphalt mixtures are necessary, in this sense this research is complementary to the studies of Faccin (2018) and Schuster (2018) that analyzed the resistance to deformation and fatigue behavior in the same mixtures. The present research contributes to the construction of a database with the characteristics of 24 mixtures prepared and used in RS. In this work, the scope is to verify the susceptibility to induced moisture damage of dense asphalt mixtures produced and applied on highways in Rio Grande do Sul on viscoelastic approach. For this, the collected aggregates were submitted to the tests of petrographic analysis, fluorescence of X-rays and of adhesiveness to the bituminous binder. Induced moisture damage and complex modulus with application of the protocol of damage by induced humidity in two cycles. The 2S2P1D mathematical model (2 Springs, 2 Parabolics, 1 Dashpot) developed by Olard and Di Benedetto (2003) was used to analyze the performance of the viscoelastic properties. The 12 rock samples were evaluated and classified with the use of petrographic scale tests, X-ray fluorescence and adhesiveness to bituminous binder. A comparative analysis was then carried out between all the results, resulting in a ranking for classification in terms of visual adhesiveness ranging from excellent to poor. In the Induced Moisture Damage test, the mixtures showed values that indicate loss of resistance due to induced humidity. However, they all meet the established limits, indicating that there are no major problems in the mixtures produced in RS in terms of the deleterious effect of water. After damaging cycles induced humidity, an increase of the phase angle and decrease in the modulus values are observed indicating a decrease in stiffness, that is, loss of viscoelasticity, prompting for the decrease of the capacity of the binder inside the mixture caused by the loss of between the components, completely modifying the distribution of forces within the structure. Through the complex modulus test significant differences in rheological behavior were observed, even for mixtures with the same type of binder after cycling. It is also observed, after the cycling, an increase of the phase angle and decrease in the values of modulus indicating drop in stiffness. It was also noted a greater spacing of all curves after the cycles of damage, being more expressive in the blends utilizing CAP 50/70, indicating that blends with conventional binder are more susceptible to water-depleting action than those with modified binder.