اداء خصائص الخرسانة الاسفلتية ذات التدرج المفتوح لرصفات الطرق

CHARACTERIZING OPEN GRADED FRICTION COURSE PERFORMANCE FOR HIGHWAY PAVEMENTS

    Nowadays the asphalt technology is developing steadily to satisfy the generated need for integrated highway services. Open Graded Friction Course (OGFC) is an asphalt mixture identified by elevated air voids content that is used over traditional Dense Graded pavements to gain frictional, safety and environmental benefits. Essentially, OGFC offers significant advantages like drain storm water effectively, roads safety (high skid resistance), control noise pollution, and reducing city ambient temperature. However, it has many other disadvantages like: low permanent deformation resistance, low fatigue strength, high stripping and moisture susceptibility, in general, it is not as good as the common dense graded mixtures.

    In this research, the efficiency of adding Polymer Modified Asphalt (PMA) (prepared in the laboratory from local asphalt with developed Styrene Butadiene Styrene (SBS) to maximize the rheological properties and to minimize asphalt degradation for OGFC mixtures was assessed. The developed polymer includes silica inherently, so the binder upgrading was planned to be from micro network formulation after polymer setting, and further reinforcement initiated from silica particles. However, low binder stiffness was controlled and binder enhanced significantly. In this study proved that adding 6% of developed polymer increased the viscosity by 377%, and that led to decrease the draindown by 98%.

    The PMA was used in different percentages with the range of binder content to produce different mixtures, these mixtures were characterized and compared with a traditional OGFC mixture. The characterization included volumetric, mechanical and durability properties of the produced mixtures, further to the main functional properties like noise and skid resistance. Therefore, variety of standardized and non-standardized test methods was conducted for this purpose; namely, Indirect Tensile Strength (ITS), moisture susceptibility, permeability, Cantabro, Marshall stability and flow, Wheel track test, draindown, skid resistance, and noise reduction tests.

    Results proved that the incorporating of polymer generally upgrade the volumetric, mechanical, durability and functional properties of the produced mixtures. For OGFC mixtures have 6% binder, the permeability increased from 31 to 54% depending on polymer percentage. Also, it improved the permanent deformation resistance by about 86 %, furthermore it controlled the draindown rate by about 98 %, while skid resistance improved by 80 %. Additionally, the use of polymer increased the Indirect Tensile Strength (ITS) by 30 %, also the moisture susceptibility resistance decreased by 19%, the sound absorption coefficient became higher by 14.9%. Other complementary test results in this research support the effectiveness of (PMA) mixtures, as will be shown through the thesis parts.

    On the other hand, in this research selective OGFC properties were statistically modeled, depending on mix design inputs for two purposes; prediction and mix inputs significance. Principally, ITS, water sensitivity, and permeability were selected from mechanical, durability, and volumetric properties, respectively. They represent the dependent variables for each model, while fillers as (CMF, or OPC), binder content, and polymer content represent the independent variables for all models. The generated models offered vital achievable tool for prediction (e.g., their R² are 0.781, 0.821 and 0.820, respectively, for the mentioned model’s properties). Also, it helped to scale the significance of each independent variable (e.g., filler type significantly affects water sensitivity properties, their correlation was 0.752).

    However, the findings of the test results and modeling ensure the significant use of PMA to overcome the shortcoming of the traditional OGFC in terms of volumetric, mechanical and durability properties, in one hand. While models are significant tool, on other hand. Finally, these can open a new era of using this technology in local infrastructure for best services.