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Permanent deformation or rutting is one of the most important distress modes that affect the life of flexible pavements. This type of distress is often observed on the roads that are situated in tropical regions. The properties of the constituent materials play a significant role in the construction properties of the pavement. The use of porous gradation and high binder grade for proper binding in the structure of mixes is known as the methods for improving the properties of mixtures. One of the mixtures made on this basis is Stone Matrix Asphalt mixtures (SMA). These mixes are a type of hot mixed with the coarse skeleton and the high binder and filler, which plays a key role, with the importance of the type and the tar properties used, as the binder of rock particles and the factor that has to endure the stress of the shear stress between aggregates.  On the other hand, due to the high percent of binder and the prevention of binder, the use of additives such as fibers or polymer materials is inevitable. The use of polymeric additives in addition to improving the binder properties, with the increase binder viscosity, also decreases binder drain down. Also, one of the recently applied additives to enhance the binder properties is Nano - clay. The aim of this study is to evaluate the effects of Nano clay as the main additive to binder to improve the binder properties alongside the SBS and fibers, in order to increase the loading resistance of asphalt and to correct its technical properties against the rutting. So, control asphalt mixtures containing of 60-70 binders with 0/4% fiber blended into mixture or modified bitumen mixed by 5 %, along with a montmorillonite additive of 1 %, 2 %, 3 % and 4 % for both pure and polymer bitumen. In this study, the Marshall test, dynamic creep tests and delamination were performed on different samples. The results of these experiments show improved performance of samples containing Nano - nanoparticles with an addition of Nano clay to 3%, which is best achieved performance in polymer modified mixtures.

Permanent deformation or rutting in wheel paths is one of the most important failure modes in asphalt pavements that affect the pavement life. Permanent deformation in asphalt mixtures can be defined as the unrecoverable cumulative deformation that occurs mainly at high temperatures in the wheel paths as a result of repeated traffic loading. The deformation results in depressions on the pavement surface along the wheel tracks relative to other points on the surface. Permanent deformation in wheel paths is one of the fundamental defects that occur due to lack of bearing capacity in flexible pavement layers. This type of defect usually occurs in the roads in the tropical areas. Rutting occurs due to cumulative non - reversible Permanent deformations in the pavement layers under repeated traffic loading. In order to increase pavement life and consequently decrease maintenance related traffic delays، great demands are placed on permanent deformation resistance of asphalt mixtures. Hot Mix Asphalt is composed of aggregates and asphalt binder. Properties of these materials have important effects on the pavement structure performance. Although، asphalt binder is a little part of mixture (in comparison with aggregates)، but has major effects on the performance، durability and stability of the asphalt concrete mixture. Any change in asphalt properties will result significant changes in the asphalt concrete mixture performance. Since asphalt cement (AC) never fully satisfying lacks the physical and mechanical properties، researchers are constantly trying to improve the asphalt cement properties. Asphalt cement modification will result improved quality and increased life of the pavement. Nano - particles is one of the additives that are used to modify the properties of asphalt cement. Nano - clays are unique materials as additives to make significant improvements in the material properties of polymer Nano -composites. Nano-clay polymer materials typically strengthen the mechanical properties، modulus and stability of these cases. In this research، it is assumed that subgrade، sub-base and base layers of flexible pavement have sufficient resistance to rutting. Nanoclay is used to modification of bitumen properties for Hot Mix Asphalt mixtures better bearing capacity and resistance to rutting. So، limestone aggregate with 4 degration number، AC 60-70 and two types of montmorillonite Nanoclay: Cloisite 15A and Cloisite 30B are used in this study. Marshall and Dynamic creep tests in two stress levels (300 and 450 KPa) at 50 ° C، as well as rutting test on the HMA samples with 0، 2، 4 and 6 percent of each Nanoclay were performed. Test results show that adding Nanoclay will result the better performance of HMA samples.