The Performance Evaluation of Porous Asphalt Mixtures Reinforced by Fibers

Environmentally friendly porous asphalt mixtures have poor tensile strength performance and durability due to their porous structure. This results in their service life typically being less than ten years. Reinforcement with fibers can be a possible solution to structural weaknesses in porous asphalt road surfaces. Fibers have been proven to be an effective additive in improving the mechanical performance of asphalt mixes, but little attention has been paid to porous asphalt mixes. This study investigates the effect of four different fibers; (a) polypropylene fiber, (b) glass fiber, (c) basalt fiber, and (d) crumb rubber, on the functional and mechanical performance of porous asphalt mixtures. Fibers were used in four different percentages (0.2, 0.4, 0.6 and 0.8%) according to the mix aggregate weight. The experimental test plan includes the characterization of air voids for permeability, Cantabro particle loss, indirect tensile strength, and moisture sensitivity. Type-3 gradation (in Turkish Highways Technical Specification) was chosen as the mixture gradation. Mixture specimens were prepared using a Marshall compactor in 6.0 and 6.5% polymer-modified bitumen. Test results show that void and permeability generally decrease with increasing fiber content, except for polypropylene fiber. Cantabro particle loss was significantly reduced for all fibers at 6.5% bitumen compared to 6.0%. Minimum wear loss value was obtained in 0.2% basalt fiber. Indirect Tensile Strength (ITS) improved significantly for all fibers. The ITS of 0.2% basalt fiber was enhanced by 124% compared to the control specimens. The optimum fiber contents were determined as 0.2% for basalt fiber and 0.4% for glass fiber.