خواص طبقة الخرسانة الاسفلتية ذات التدرج المفتوح باستخدام اسفلت معدل بألياف هجينة

CHARACTERIZING OPEN GRADED FRICTION COURSE LAYER INCORPORATING HYBRID FIBER MODIFIED BINDER

Abstract

In the current era, the world is witnessing a great development in asphalt mixtures, commensurate with road services to avoid the issues had occurred. Therefore, the use of modified Open Graded Friction Coarse (OGFC) is very important to provide high quality road services and to avoid some problems. This type of asphalt mixture is characterized by its coarse gradation and few fine materials, which provides a high percentage of voids for the structure of a mixture. The most important findings of practical research to benefit from OGFC layer can be summarized as: effectively draining rainwater, road safety (high slip resistance), reduce noise pollution, reduce the urban heat, etc. Nevertheless, this layer also contains certain disadvantages, including: decreased resistance to permanent deformation, low fatigue strength, high stripping, and moisture susceptibility. In addition, this type of mixture may be accompanied by the occurrence of the “draindown” phenomenon as a result of the high design percentages of asphalt, so researchers resort to the use of improved asphalt binder for the purpose of improving the performance of this type of mixture and increase its service life.
This research focuses on studying the effect of waste materials on the performance of OGFC asphalt mixture. Currently, the use of modified materials that must meet the sustainability concept is increasing; in terms of low cost, conservation of natural resources, and reduction of environmental concerns. First step in this research included the selection of the OGFC mixture with the optimal asphalt content (OAC) representing the control mixture (CM) in the whole research which was valued at 6.5%. Then, the OGFC was improved through three phases. First and second stages included the development of asphalt binder using Waste Paper Fiber (W-PF) and Recycled-Low Density Polyethylene (r-LDPE) individually, at four different dosages W-PF 0.3%, 0.5%, 0.7%, while r-LDPE 3% as a part of total bitumen weight. The third stage included the usage of
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mentioned materials collectively in different ratios; namely, (0.3+3) %, (0.5+3) % and (0.7+3) % as a part of total bitumen weight. All modified asphalt types were characterized using common physical properties (i.e. penetration, softening point, ductility, penetration index and loss on heat). The developed mixtures were characterized using a set of volumetric properties (i.e., bulk density, air voids, porosity, voids in mineral aggregates, voids filled with asphalt, and draindown), functional and mechanical properties (i.e., permeability, indirect tensile strength, creep compliance, skid resistance, Cantabro, and wheel track), and durability properties (tensile strength ratio, and Cantabro aged/unaged ratio).
The use of modification materials displays an enhancement in the physical properties of asphalt binder. Where all materials resulted in reduce penetration depth, ductility, and temperature sensitivity of bitumen, and increase each of softening point, viscosity, and aging resistance of bitumen. The use of modified materials, consequently, showed a positive effect on the OGFC mixture performance. The use of r-LDPE showed the best performance of OGFC mixture especially in the case of permeability, indirect tensile strength, rutting, and Cantabro loss, followed by mixtures with Mixed Dosage MD. Meanwhile the usage of W-PF displayed the lower enhancement. For example, the amount of improvement in the mixture performance attain 18%, 37%, 35% and 30% for permeability, resistance to tensile cracking, abrasion loss, and rut depth, respectively, when asphalt was modified by r-LDPE, in addition to the enhancements of other properties. However, results enforced the significant of incorporating the waste materials in modifying asphalt binder for OGFC mixture; In the other words, it can be concluded that sustainable OGFC can introduce using such waste materials.