Experimental Study on the Possible Use of Waste Tire Powder as Mineral Filler in Hot Mix Asphalt

Abstract

Construction and upgrading highway roads are increasing in Ethiopia and majority of the roads are flexible pavement type. Flexible pavement road consists of asphalt pavements whose maintenance and further expansion depends upon availability of natural resources like aggregates. One of the most commonly used materials as filler is crushed stone dust from the crushing aggregate but their incessant use in asphalt mixes has led to their scarcity. Therefore, it is important to see an alternative non-conventional filler material. This research focused on evaluating the possible use of waste tire powder as mineral filler in hot mix asphalt. To determine the Optimum Bitumen Content three identical hot mix asphalt specimens were prepared for (5.0%, 6.0%, and 7.0% crushed stone dust by weight of aggregates) and five different percentages bitumen content (4.0%, 4.5%, 5.0%, 5.5%, and 6.0% by weight of total mix). Following NAPA (National Asphalt Pavement Association) method the optimum bitumen content and optimum filler content were selected. Six varying percentage of waste tire powder by weight of optimum filler content with a rate of 0% (control), 3.0%, 6.0%, 9.0%, 12%, 15%, and 18% were prepared using optimum bitumen content to obtain the optimum replacement percentage. The study compares the performance of asphalt mixes using Stability, and flow with corresponding volumetric properties, and moisture susceptibility using Indirect Tensile Strength (ITS) test. Finally, the effect of waste tire powder on the bitumen content was evaluated using optimum waste tire powder at a bitumen content of two above and below the optimum at 0.5% increments, and compared with the control mix. A total of 105 HMA specimens were prepared. From those specimens, 45 were for the control mix, 18 were for replacement; 12 were to check the effect of waste tire powder on bitumen content and 30 for Indirect Tensile Strength test. From the test results, the optimum replacement percentage of waste tire powder found at 12% by weight of optimum filler content (6.0%) at a bitumen content of 5.0%. Asphalt mixes prepared with waste tire powder filler are not sensitive to the action of water and resulted better resistance to moisture-induced damage. Based on the obtained results waste tire powder can also be used with 4.5% and 5.5% bitumen content. 12% waste tire powder achieves the minimum requirements of local Specifications (Ethiopian Road Authority) and international Specifications (Asphalt Institute). It can be concluded that waste tire powder can be used as filler materials instead of most commonly used crushed stone dust filler.