Desempenhos de misturas e ligantes asfálticos modificados com borracha moída de pneus e copolímero SBS quanto à fadiga e à deformação permanente: estudo de caso na rodovia SC-163

Abstract

Amongst the highways that cross through the Santa Catarina State, the SC-163 one is worth to be mentioned. This highway connects the states of Santa Catarina and Rio Grande do Sul and it also performs as an agribusiness production output route between the Southern and Middle West regions of Brazil. Despite such an importance, specific segments of the SC-163 highway showed a poor conservation status, which was noticed after field observations according to protocols standardized by the National Department of Transport Infrastructure (DNIT). In this manner, the main goal of the present study was to perform a comparative analysis of the rutting and fatigue performance of asphalt mixtures and binders with no additives (AC 50/70), modified with 15% of crumb rubber (AC+rubber) and modified with 5% of styrene-butadiene-styrene copolymer – SBS (AC+SBS). A new pavement design of the SC-163 highway was also made by considering the input data from the subgrade soil and the underneath layers, estimated traffic within 10 years and the new Brazilian Mechanistic-Empirical Pavement Design Method (MEDINA). The binder experiments included oscillatory shear, multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests. The mixture experiments included resilient modulus (RM), uniaxial repeated creep (flow number), splitting tensile strength and indirect traction tests. The subgrade soil was characterized by granulometric curves, Atterberg indices, California Bearing Ratio (CBR), permanent deformation and RM. The use of the MEDINA method resulted in a surface layer with a suggested thickness of 13.5 cm in the case of mixtures prepared with asphalt-rubber, which is 30.5% higher than the one suggested by the DNER method. It should be mentioned that this thicker layer is essential to avoid premature failure of the pavement by fatigue cracking and rutting. Moreover, the flow number results recommended the use of the AC+SBS or the AC+rubber in the field pavement, rather than the AC 50/70. The outcomes of the LAS tests provided good correlations with the fatigue lives of the mixtures, and the flow number data tended to correlate with the ones from MSCR. The MEDINA method is recommended when selecting a new surface layer for the SC-163 highway, and also that this layer be prepared with an asphalt binder modified with SBS copolymer or crumb rubber. In addition, the promising findings of the LAS and MSCR tests in the estimation of the rutting and fatigue performance of binders in the field pavement are deserved to be mentioned.