Avaliação da permeabilidade de misturas asfálticas com diferentes granulometrias

Abstract

The water can reach the pavement in various ways such as by precipitation or capillarity in the form of water vapor, among others. The deleterious effect of water is a major factor responsible for the distresses in flexible pavements. Inside the structure, the water can interfere with adhesion of the binder film with the aggregate and the cohesion of the binder film itself, exacerbating damage mechanisms such as fatigue and permanent deformation. On the pavement surface, the water can cause practical problems such as the phenomenon of hydroplaning, a major cause of accidents on rainy days. Thus, studying the behavior of the pavement in the presence of water is crucial to predict the behavior of this structure. An important parameter to verify the quality of the pavement with respect to water flow is the permeability of the material. In Brazil, there is no established methodology for determining the coefficient of permeability of asphalt mixtures. In this context, this paper aims to propose a methodology to evaluate the permeability of different asphalt mixtures, as well as check some factors affecting the permeability of the same. For this purpose, three types of asphalt with different air voids (Av) mixtures were analyzed: two with dense gradation Asphalt Sand - AS (7% and 9% Av) and Asphalt Concrete - AC (4% and 7% Av) and one with open gradation Porous Friction Layer - PFL (20% and 23% Av). The results show, as expected, that the measure increase the Av the permeability also tends to increase. For mixtures of dense gradation (AC and AS), the influence of Av was more relevant, also, for mixing the AC type was change in the order of magnitude of permeability values with increasing (average) of 3% in Av. As for the mixture with open gradation (PFL), the permeability results for both Av evaluated were substantially equal. Moreover, it appears as the Nominal Maximum Aggregate Size (NMAS) of the aggregate used increases, the permeability of the asphalt mixture tends to increase. Another important factor that influenced the results of permeability was the degree of saturation of the samples. As the saturation increases, the permeability of the material also increases. Regarding the proposed test method, it appears that the order of magnitude of the values obtained in this work for the three mixtures evaluated were similar to the magnitude found in other experimental methods reported in the literature. This fact serves to prove the reliability of the proposed method.