Concretos asfálticos em utilização no Rio Grande do Sul: comportamento mecânico e desempenho em campo quanto à deformação permanente

Abstract

Highways are relevant to the economic and social context in the state of Rio Grande do Sul (RS), located in the southern region of Brazil. Flexible pavement with asphalt concrete layers is the most commonly used solution for the construction and repair of highways. The mechanical behavior of these asphalt mixtures depends on, among other factors, the constituent materials, traffic and climate. It is directly related to field performance, which is expressed by the mechanical properties typically obtained in laboratory tests. Understanding the behavior of the mixtures used in the state is of utmost importance in the design and specification of pavement layers. Also, it is useful for analyzing alternatives, especially for understanding resistance to permanent deformation, which is one of the causes of damage to state highways. The aim of this study was to evaluate the mechanical behavior of different dense asphalt mixtures used in RS in laboratory and field tests. The focus was on permanent deformation and flow number obtained by the uniaxial repeated load test. Twenty-four asphalt concrete samples were collected in different regions of the state, with different aggregates and asphalt binders, as well as several grain size ranges recommended by the road agencies that oversee the state highways (DAER and DNIT). In addition, fifteen stretches of road were monitored to evaluate permanent deformation of the layers. The analysis of the results shows variation in grain size and binder content for most mixtures produced in RS. We also identified the use of outdated aggregate and binder selection methods, dose criteria and parameters such as tensile strength (TS). The fact that they do not take performance into account shows the need to update the current specifications. The results of the mechanical properties show significant differences in behavior for the stiffness of the mixtures. This shows the importance of effective characterization of the properties for pavement projects. The flow number test showed strong correlation between FN and the rheology of the mixtures. This characteristic is strongly influenced by the type of binder, followed by the percentage of stone dust. In addition, the flow number criteria of the uniaxial repeated load test were refined according to traffic. Thus, the use of FN appears to be promising in predicting permanent deformation of asphalt concretes, except for warm mix asphalt and rubberized asphalt, which have low FN values and good field performance.