Desempenho mecânico de misturas asfálticas do tipo stone matrix asphalt com uso de fibras amazônicas e agregados de resíduos de construção e demolição

Abstract

The development of road infrastructure in Brazil, coupled with investments in the automotive industry in the 60s, boosted, years later, the need to implement public and private administrative systems on these roads, in order to maintain good traffic conditions and safety. Moreover, Manaus county has a history of geotechnical problems, such as the costly process of obtaining stone material, due to the thick layers of fine soil overlying rocky horizons and the complicated logistics of its transportation. These facts, on both national and regional levels, have led to the study of asphalt mixtures with improved mechanical performance, according to the scientific literature on commonly used mixtures, for example, Asphalt Concrete. These are discontinuous mixtures with excellent experience, especially on European roads, called Stone Matrix Asphalt (SMA). SMA is characterized by a high percentage of coarse aggregate, which favors the draindown of mastic asphalt. To reduce this effect, fibers from the Amazonian curauá were added, which are largely produced in the northern region of Brazil and characterized by high mechanical resistance, although mainly applied in automotive composites. In addition, to enable the use of this type of bituminous coating due to the large proportion of coarse materials, we analyzed the performance of a recycled aggregate (Construction and Demolition Waste - CDW) compared to a traditional granite aggregate. In this scenario, there was physical and mechanical characterization of the component materials and of the SMA mixture. With respect to the aggregates, the CDW achieved 160% more Los Angeles abrasion, satisfactory adhesiveness and lower bulk and saturated densities when compared with brita. The mineral mixture, 75% coarse, 15% fine and 10% filler, fit the specifications described by the National Asphalt Pavement Association (NAPA). Inferring a void volume of 4%, meeting the requirements of the empty coarse fraction of the aggregate in the compacted mixture, larger than the empty coarse fraction of the compacted aggregate, similar levels were obtained for the CAP project if using Marshall type dosage, at 6.28% (for SMA with brita), 6.82% (for SMA with CDW), 6.50% (for SMA with brita and curauá) and 6.88% (for SMA with CDW and curauá). Draindown was effectively reduced by curauá fibers with only 0.3% fiber in both asphalt composites. With regard to traction resistance performed at 25 °C, 40°C and 60°C, the composite CDW obtained better results, but fiber insertion lowered the values, possibly by loss of rigidity due to the detriment of their adsorbed water. However, in the Resilience Modulus performed at 25°C and 40°C, in general, fibers contribute to the mechanical behavior, especially the mix with brita and the temperature at 40°C. Increased temperature caused decreased results in both mechanical tests, but the decrease was less in the recycled aggregate. In view of this, a good performance of the recycled aggregate is assumed in SMA blends, with positive results from the addition of curauá fibers particularly as to the resilience of the material.