Avaliação da faixa de agregados dominantes e componentes intersticiais em misturas asfálticas

Abstract

The definition of the aggregate gradation of an asphalt mixture conventionally follows empirical procedures, reproducing aggregate proportions of previous design projects or defining a new curve, usually by trial and error, so as to meet gradation specifications based on experience. The dominant size aggregate range (DASR) is a gradation selection method with criteria based on granular interlocking and DASR porosity, considering also the so-called interstitial components (IC), which are smaller aggregates than the DASR. The key concept of the method is the existence of a range of dominant large aggregates that is responsible for resisting permanent deformation. The literature reports a good correlation between this type of distress and the uniaxial repeated load test, which results in the Flow Number (FN). This work AIMS to analyze the influence of the origin and gradation from the DASR parameters and the Interstitial Components (IC) (aggregates with smaller diameters than the last dominant coarse particle), as well as the type of binder and the mixture design, in the FN results. The objective is also to explain the behavior of mixtures with porosity values within a specific range, but resulting in FN with great oscillations, and to verify which factors generate such inconsistencies. A database was composed of 52 mixtures containing aggregates with different mineralogy, coming from 3 different Brazilian states. DASR parameters (interlocking, percentage of FAD aggregates) first and then DASR-IC parameters (Break Factor and Fine Aggregate Ratio) were correlated with the FN of mixtures containing aggregates with equivalent mineralogy and interlocking, the same type of binder and design method, differentiated only by the percentage of aggregates in the DASR. Different characteristics of the blends were then considered from the organized database until all these characteristics were evaluated. It was possible to analyze each parameter and its consequent impact on the FN results, including the mixtures within the so-called marginal porosity range. The results showed that the DASR methodology is able to evaluate and specify asphalt mixtures gradation to resist permanent deformation, provided they have the same characteristics. For better formation of the gradation curve, not only the interlocking should be analyzed, but also the DASR and DASR-IC parameters, and the mix design characteristics. Changes in gradation and design parameters may have significant effect on FN results. Finally, there is a contribution to the elaboration of particle size ranges, evaluation and selection of aggregates, showing their impact on the response of the uniaxial repeated loading test, depending on the binder type and content.