Modeling Asphalt Mixture Cohesion and Internal Friction Angle Using Marshall Parameters

National road network constitutes a major part of each country's wealth and huge investments are spent in this sector annually on pavement maintenance, repair and rehabilitation. One of the most widespread damages in flexible pavements is rutting, which is due to weakness in shear resistence of the asphalt mixture. The best approach to prevent such malicious phenomenon is to use mixtures in which the amount of effective parameters in shear resistence of the asphalt is controlled. Cohesion (C) and internal friction angle (f) of the asphalt are the final determinants of pavement shear resistence. The best way to determine C and f in asphalt is to perform triaxial test on asphalt samples. But, for some reasons, such as high costs to perform this test, as well as the lack of triaxial­­ test equipment in the country, performing this test is virtually impossible. On the other hand, Marshal equipment is readily available in the most remote workshops and it is being used extensively in Iran. Therefore, in this research, it was tried to find some relationships between C and f in asphalt with Marshall parameters. The obtained relationships showed that there is proper relation between asphalt shear stress parameters and Marshall stability and flow. By using these relationships, concurrent with presentation of the mixing design in the laboratory and before mass production of the asphalt, the limits of C and f are determined, too. Therefore, mass production of the asphalt with high rutting potential could be prevented.