Developing countries like Turkey are trying to implement the Mechanistic-Empirical Pavement Design Guide (MEPDG). The implementation of this method requires comprehensive local data collection, evaluation, and, if necessary, a local calibration. The objective of this study is to prepare local data such as climate, traffic, and materials for evaluation and local calibration of MEPDG for Izmir City. For this purpose, the climate and traffic data were obtained, analysed, and converted to the MEPDG format. Besides, the bound and unbound pavement material properties were determined. Since some of the obtained local data like climate, vehicle classification, traffic growth factor, and axle load distribution cannot be directly used as design inputs, they were developed and converted to a suitable format to be used in the MEPDG. The output of this study can be used as design inputs for the evaluation and local calibration the MEPDG in Izmir and serves as a guide for data preparation for other parts of the country.
The depletion of natural aggregate sources which generally accounts for a huge percent of Hot Mixed Asphalts (HMAs) and the difficulty posed by disposal scrap tires are a major environmental concern for the future. The use of waste products like scrap tires in highway construction is considered a sustainable way of dealing with these issues. Crumb rubber is a material pulverized from waste polymer products like scrap tires which are then added to HMAs to improve their performance. This study focuses on the sensitivity of crumb rubber particle sizes (fine ≤1.18 mm), (coarse ≥1.18 mm and ≤3.35 mm) (and mix of 50% fine and 50% coarse) and partial replacement (1.5 and 2.5% of total weight) of aggregates on the Marshall test parameters of rubberized asphalt mixes. The Marshall test parameters: density, stability, VTM, VFB of both rubberized asphalt and conventional asphalt samples were compared and also the Asphalt Institute (AI) and National Asphalt Pavement Association (NAPA) methods were used to obtain the optimum bitumen content (OBC). From the results, it suggests that; the utilization of dry process methodology of adding crumb rubber additives in different sizes and percentages had a considerable effect on Marshal test parameters and also influences the optimum binder content estimates. The results of this study can be used as a reference point for the use of crumb rubber in HMAs.
The scope of this study was to assess the predicted impact of design factors (voids percentage (Va), effective binder content (Vbe) and aggregate gradation) in each asphalt concrete (AC) layer on pavement performance for conditions in Izmir, Turkey. Research was conducted on three flexible pavement structures for three traffic levels and three subgrade types using AashtoWare Pavement ME Design software. The results indicated that increasing Vbe (from 8% to 15%) and Va (from 3% to 5%) in the wearing course resulted in, respectively, almost 1.0 mm and 0.2 mm increases in AC rutting depth, 17 m/km and 145 m/km reductions in thermal cracking length and a 55.8 m/km decrease and 85 m/km increase in top-down cracking length. For the binder course, an increase in Vbe (from 7% to 14%) and Va (from 4% to 6%) led to, respectively, nearly 1.0 mm and 0.3 mm increases in AC rutting depth and a 35 m/km increase in top-down cracking length. For the AC base course, an increase in Vbe (from 6% to 12%) and Va (from 5% to 6%) resulted in a 26.3% reduction and 14.2% increase in alligator cracking area, respectively. An increase in the fine aggregate percentage and a decrease in the coarse aggregate gradation in the hot-mix asphalt mixture led to improved performance.
The objective of this study was to improve the performance of flexible pavement through suitable aggregate gradation. Thus, initially, the dynamic modulus of asphalt mixtures |E*| for different aggregate gradations were predicted, and suitable aggregate gradation was determined. Then the performance of three different pavement structures for two aggregate gradations (Mid and Suitable), using AASHTOWare Pavement ME Design 2.5. 5, were evaluated for local conditions of Izmir, Turkey. The analysis result revealed that using suitable values compared to middle values increased the |E*| and improved the rutting and fatigue resistance of all pavement structures for any traffic levels. The output of this study can be used as a guide for hot mixed asphalt mix design and pavement design based on Mechanistic-Empirical Pavement Design Guide as well.
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