Comportamento de misturas asfálticas modificadas com borracha

Abstract

Although it represents only a small portion by weight of asphalt mixtures, the bituminous binder plays a fundamental role in the connection between the aggregates and in the waterproofing of the coating with fundamental properties for the mechanical performance of the coating layer. The physical and mechanical properties of conventional binders can be improved with the addition of polymers, such as rubber. This research aims to evaluate by the Marshall methodology the influence of rubber acting as a modifying agent in the binder when used in asphalt mixtures. In order to evaluate the performance of the rubber, samples of CAP 50/70 (control) and samples were made using the binder modified with rubber Ecoflex B 3G using the content range of 4.5 % to 6.5%. Opted to work with a mixture of the type CA (asphalt concrete), framed in the C range (DNIT 031/2006 - ES) for the bearing layer. With the characterization of the aggregates performed, the Marshall parameters were obtained in sequence and there was a definition for the design content of both mixtures. The mixtures were then submitted to the tensile strength test by diametrical compression and the values for Marshall quotient and tenacity were also obtained. It was observed for the mixtures with Ecoflex B 3G an improvement in most of the observed parameters, mainly for stability, and tenacity. The data obtained during the experimental campaign for conventional and modified samples provided subsidies for a statistical evaluation comparing both mixtures by levels of significance. For the conditions analyzed, the values for stability of the rubber-modified mixtures were 25,1% higher than those with CAP 50/70 with a good level of significance. Higher values, on average, for the modified mixtures were also found for fluency and tenacity (33,3% and 11,6%, respectively), although without sufficient levels of significance. The results for the Marshall quotient (21% higher for modified mixtures) proved to be inconclusive and additional tests are needed. Finally, both mixtures showed very close values for tensile strength (with a value, on average, 2,7% higher for the modified ones), being, therefore, statistically similar.