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Studying the stress, strain and deformation in pavement under traffic loads is one of the most important areas in pavement engineering. Tensile strain in the bottom of asphalt, leads to the most common type of failure (fatigue); therefore, it is an important parameter to be analyzed. In this study, the pavement structure has been analyzed and then for validation, the output in all elements and points were compared to the field results obtained from University of Pennsylvania. The further studies were conducted by 3D program which indicated a good agreement with the results from field and the first finite elementbased program. In static and quasi-static loadings, the maximum strain were observed exactly under the load center, while in dynamic loading, unexpectedly, the maximum value occurred behind the load center, and the distance increases by increase of vehicle velocity. This study includes the effect of load speed on tensile strain in asphalt sub-layer.

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In the recent years, by replacing a part of our country's asphalt pavements with concrete pavements, it is necessary to perform appropriate actions in order to preserve and repair destructions (due to executive weaknesses, loading and environmental conditions) during pavement lifetime. In order to increase mechanical properties and durability of repair mortars, micro-silica and zeolite were used as pozzolan, polypropylene fibers for controlling crack (due to fluctuations in concrete and temperature change) and the cement type 3 for obtaining high resistivity in short-term. In this study, 11mixing designs were investigated, and the composition of polypropylene fibers with micro-scale thickness with cement complements can be considered as the most optimal mixing design in 0.2% of fibers with 10% micro-silica and 15% zeolite in order to promote effective parameters of elasticity modulus, modulus of rupture and decrease of contraction in repair mortars of concrete pavements. By adding polypropylene fibers, the samples were not completely ruptured in the tension of primary strength that they showed. The samples containing 0.4% fibers with deformation from spherical state to elliptical state with splay value in rupture surface showed individual characteristic which caused minimizing rupture and crunch in the repaired area.

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Asphalt concrete is composed of stone, sand, filler, and asphalt binder. Fatigue can be considered as a phenomenon affecting both the binder (asphalt binder or mastic) and the mixture. The purpose of this study was to investigate the fatigue damage response in asphalt binders, mastics, and asphalt concrete mixtures modified with nano-silica and synthesized polyurethane. The continuum damage mechanics method and phenomenological approaches in this study were used to investigate the fatigue performance. Obtained results indicated that the effect of the synthesized polyurethane on improving the fatigue life was far greater than that of nano-silica. The damage process in asphalt binders differed from that in the mastic and asphalt concrete mixture. Damage intensity parameter is an appropriate criterion for evaluating fatigue performance of asphalt binders and mastics. Concerning the fatigue of asphalt concrete mixture, the results of this study indicated a better convergence between the fatigue parameters of mastics and asphalt concrete mixture compared to asphalt binders, especially with increasing aging. Also, there was greater convergence between the fatigue life of the asphalt concrete mixture and asphalt binder and mastics in the method of continuum damage mechanics as compared to the phenomenological approach.