Uniformity and mechanical properties of dense asphalt concrete with steel wool fibers

Fibers in asphalt concrete are known for enhancing its strength and fatigue characteristics while increasing ductility. Additionally, fibers may increase the dynamic modulus, moisture resistance, creep compliance, rutting and freeze-thaw resistance of asphalt concrete, preventing the formation and propagation of cracks. The addition of fibers may influence the properties of the material, but it is not clear how is this influence, and which are the optimum amount, length and diameter of fibers needed for not having a negative impact on the mixture. For this reason, fibers (steel wool) distribution and their effect on the porosity. and electrical conductivity of dense asphalt concrete have been studied. With that purpose, 25 different mixtures, with the same aggregates gradation and amount of bitumen, but with two different lengths of fibers, four different percentages, and four different diameters of steel wool have been built. Results show that long and thin fibers produce many clusters and a poor distribution, while short and thick fibers disperse very well in the mixture. It was also observed that fibers can be seriously damaged during the mixing and compaction processes. Finally, it has been found that steel wool fibers do not have a relevant influence on the particle loss resistance and flexural strength of dense asphalt concrete. (C) 2013 Elsevier Ltd. All rights reserved.