Abstract
ABSTRACT In the new Brazilian mechanistic-empirical design method of asphalt pavements, MeDiNa, the characterization of permanent deformation (PD) for the selection of soils and gravel is based on tests performed with at least 150,000 loading cycles for each of the nine specimens indicated in the DNIT standard. Despite providing information about the material behavior under a wide range of testing conditions, the experimental program related to these PD characterizations is time consuming and it is believed that it can be optimized. This paper evaluates the influence of the number of loading cycle applications on the characterization of the materials. For this purpose, seven materials were analyzed at their optimum moisture content (OMC) and one of them was also compacted in a condition above the OMC, in a total of eight data sets. Statistical regression analyzes were performed to identify the parameters of the predictive model for different numbers of cycles and the PD predictions for the different materials were compared. From these results, simulations were performed in the MeDiNa software to predict the performance of the materials. Four different N values were evaluated, considering 150,000 cycles as reference: discarding the 500 first cycles, but considering the PD accumulated in that interval; discarding the 500 first cycles and considering the PD accumulated in that interval; final N of 80,000; and final N of 100,000. For the analyzed materials, no significant differences were observed in the PD prediction, even considering tests with 50,000 or 70,000 cycles less than the 150,000 cycles required in the standard. This indicates that, although characterization is recommended following standardized procedures, the experimental program of the current PD standard can possibly be significantly optimized by reducing the number of cycles applied to materials in laboratory tests. This possibility must be analyzed for each material.
Highlights
Fatigue cracking of surface course is among the main of distress mechanisms of the pavement [1]
In Brazil, pavements have often been designed using empirical design method prescribed by the National Department of Transport Infrastructure - DNIT [3], based on the CBR test, on design curves developed by the United States Army Corps of Engineers (USACE) and on data obtained from the American Association of State Highway and Transportation Officials (AASHTO) Road Test in the late 1950s, adapted by engineer Murillo Lopes de Souza [4]
From the application of the protocol contained in BERNUCCI et al [30] and using the results of the volumetric parameters "voids content (VC)" and "voids filled with bitumen (VFB)" of the asphalt mixtures of granulometric ranges B and C, the values of 4.80% and 5.20% were defined for the contents of asphalt binder in the design asphalt mixtures of these respective granulometric range
Summary
Fatigue cracking of surface course is among the main of distress mechanisms of the pavement [1]. This defect consists of a progressive degradation of the material properties due to the application of cyclic stresses which value is lower than the material resistance [1]. It is typically caused by elastic strains derived from traffic load repetitions, which leads to failure of the surface course [2]. The results derived from empirical methods do not always coincide with the conditions found in the field [5]
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