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The vast amount of waste materials such as polyester waste fibers accumulating throughout the world is creating costly disposal problem. The use of these materials was proved to be economical, environmentally and effective in increasing the performance properties of the asphalt mixture in new years. The main objective of this research was to determine whether homogeneously dispersed waste polyester fibers improve Marshall stability and rutting resistance of asphalt concrete mixtures containing various lengths and percentages of the fiber. The experimental design included the use of available aggregates, and polyester waste fibers as additives to enhance the properties of asphalt mixtures. Two fiber lengths of 1cm and 2 cm were used with four different fiber contents of 0.2%, 0.35%, 0.50% and 0.65 by weight of total mixture. The results of the experimental work presented in this paper suggested that, in general, the addition of the polyester fiber s was beneficial in improving both the stability and rutting resistance of the modified asphalt mixtures. Introduction As world population continues to increase, economic and industrial growth will continue to generate increasing amounts of waste materials. Disposal methods, whatever the form, have a direct impact on the delicate balance in the physical, chemical, and biological environments that constitute our global ecosystem [1, 2]. For many reasons, economical and environmental , the use of waste materials in construction as partial or full replacement of virgin materials has increased. Previous experience showed that the use of some waste materials such as polyester fiber has proven to be cost-effective, environmentally sound, and successful in improving some of the engineering properties of asphalt mixtures [3–6]. * Assoc. Prof., Dept. of Civil Engineering, Military Technical College, Cairo, Egypt. ** Ph.D. Candidate, Dept. of Civil Engineering, Military Technical College, Cairo, Egypt. *** Prof., Dept. of Public Works, Faculty of Engineering, Cairo University, Giza, Egypt. **** Prof., Dept. of Civil Engineering, Military Technical College, Cairo, Egypt. Proceedings of the 9 ICCAE-9 Conference, 29-31 May, 2012 TE 11 2 The textile industry, all over the world, generates millions of tons of fiber trim waste which goes into landfills every year. These fibers can provide asphalt mixtures with high stability and good rutting resistance. Several fabrics made from these fibers make excellent candidates for various Civil Engineering applications including pavement treatment and build ing. Cotton reinforcement with fiber mesh in asphalt concrete mixtures , in fiber forms was first attempted in 1934 [7] Also, metal wires were reused with the penetration of waster and asbestos was determined to be a health hazard by the Environmental Prote ction Agency (EPA) at that time. Another drawback of using fiber reinforcement was that fiberglass strands cut themselves at intersections within the mixture [9, 10]. Another alternative to these materials have been provided by the textile industry with the development of synthetic materials such as polyester. These fibers provide the same benefits that the use of natural materials, however, for a longer period of time, without known risks to the environment and human health. Other previous studies suggested the benefit of the reinforcement of surface course pavements with polyester fiber [5, 11–13]. Research performed in Mexico and Texas has shown that the addition of polyester fibers in asphalt concrete pavements will reduce reflective cracking [11, 12]. Various primary factors should be taken into account while adding any waste product in asphalt pavement [1, 13]. Initially, the life cycle cost analysis must be performed to determine the effective of each material. A second consideration is the effect on quality and performance of the asphalt pavement. It would be poor economics indeed to incorporate waste that significantly increase the cost of the pavement and at the same time shortens the service life or increase the maintenance cost. The environmental advantages over its disposal in landfills are also considered in the use of waste materials. Over 60 years ago in USA, coarsely-woven cotton layers were spread between coats of asphalt to strengthen the road surface and comfort the ride [14, 15]. The cotton served both as a binder for the asphalt cement and water -resistant cover to restrain water from seeping through cracks and damaging the road base. Several fabric types (such as polypropylene, polyester, glass, nylon, or melded varieties of these and other fibers) have been used in pavements to reduce cracking. The major fabric materials currently used in pavements in the United States is polyester. During using, the fiber must be able to withstand temperatures up to 150°C and be suitably durable to sust ain traffic after the paving process [8, 16]. Since a pavement moves in several directions under mechanical and thermal stress, the multi-directional physical properties of a non -woven polyester fiber seem to be better to the bi-axial properties of a woven material. In addition, the fiber should be lightweight, for ease in use, and highly resistance to chemicals , mildew, and fungus [13, 16, and 17]. The objective of this research was to determine whether homogeneously dispersed waste polyester fibers improve the Marshall stability and rutting resistance properties of the modified asphalt mixtures. In addition, the effect of various lengths and percentages of this fiber was investigated. MATERIALS AND METHODOLOGY The materials and experimental design proce dure used in this study are as follows: Proceedings of the 9 ICCAE-9 Conference, 29-31 May, 2012 TE 11 3 The bitumen used was AC-60/70 bitumen. This asphalt was subjected to typical standard laboratory tests. The results of these tests are incorporated in Table (1). In this investigation, polyester waste in the fiber form of length 10 mm and 20 mm was used. Crushed Limestone was used as the aggregate material. Five aggregates were blended to the target gradation and the specific gravity of this aggregate blend was determined to be 2.625 g/cm. Some properties of the crushed limestone and specific gravities of aggregates are given in Table (2). The selected gradation and the specification limits are presented in Table (3). Table (4) shows Physical characteristics of polyester fibers. The Marshall Mix Design Method was used for designing the bituminous mixtures prepared with and without fibers. A speed adjustable vertical shaft mixer was used to mix the fiber and aggregate. The utilization strategy must be coupled with environmental and energy considerations to use available materials most efficiently. The aggregates used in hot mix asphalt (HMA) were prepared by mixing the fiber in 0.2%, 0.35%, 0.50% and 0.65% (by the weight of total mixture) and AC-60/70. Aggregates with fiber and bitumen were heated separately to 165C and 155°C, respectively, and then they were mixed in a mechanical mixer. The mixture was placed in a Marshall mold and compacted by applying 75 blows on each side of the specimen at 145°C. The standard dimensions of the samples were 63.5 mm height and 101.5 mm diameter. After having cooled at room temperature for one day and then conditioned in water at 60C for 30-40 min, the samples were tested with Marshall Test apparatus. All results are recorder as an average of the results of three test specimens. To investigate the effect of polyester fibers on the properties of HMA, A control mix (without fibers) was prepared and tested according to the testing program. The optimum asphalt content for the control mix was found to be 5.35% (by weight of total mix). Figure (1) illustrates a flow chart for the experimental program. Table (1): Properties of the used binder. Pb absorbed 0 .47% Specific Gravity of Bitumen 1.02 Viscosity (min = 320) 364 Softening point (45 – 55 C ) 51 Penetration, 25C, 100 g, 5 sec (1/10 mm) 63 Table (2): Specific gravity, absorption, and (LOS) of aggregate . Filer Sand SEN-1" SEN-2 SEN-1 Type / Properties 2.066 2.458 2.54 2.54 2.55 Bulk specific gravity (gm/cm) 2.60 2.59 2.60 Saturated Surface Dry sp. Gravity (gm/cm) Proceedings of the 9 ICCAE-9 Conference, 29-31 May, 2012 TE 11 4 2.476 2.634 2.69 2.67 2.68 Apparent specific gravity (gm/cm) 9.2 2.9 1.06 1.89 1.92 Absorption (%) 20 9 19.56 LOS Anglos (%) Table (3): Aggregate gradations and required specifications . Sieve # Final Gradation Specifications min max 25 100.0 100 100 19 99.4 80 100 9.5 77.6 60 80 4.75 54.2 48 65 2.36 42.1 35 50 0.6 23.9 19 36 0.3 18.3 13 23 0.15 11.1 7 15 Table (4): Physical characteristics of polyester fibers Test properties Typical values Specific gravity g/cm 1.35 Weight, gm/m 180 Tensile strength, daN/5 cm 68 Elongation-at-break, % 38 Tear strength, N 75.6 Thermal sensitivity, °C 240°C (softens) 265°C (melts) Note: 1 daN (deca-Newton) = 10 N. Polyester Fiber Control Mix (Obtaining OAC) Proceedings of the 9 ICCAE-9 Conference, 29-31 May, 2012 TE 11 5 Figure (1): Flowchart of experimental program design RESULTS AND DISCUSSION

USE OF WASTE POLYESTER FIBERS TO ENHANCE RUTTING RESISTANCE OF ASPHALT CONCRETE MIXTURES