Due to increase in bitumen prices in the last few years in the country and romotion of the usage of concrete pavements, particularly the usage of Roller Compacted Concrete RCC in urban and suburban roads construction the application of combined pavement has been developed. Also the usage of asphalt overlay to create a suitable surface for deriving on the concrete surface is suggested. The methodology proposed in this study is using metal fibers and polymer fibers, separately, to strengthen the RCC. To increase the bending, tensile and compressive strength of concrete to reduce cracking and failure of the concrete RCC could be a preventive agent. For this study, first, roller concrete mix design was developed and was built as an indicator of tensile strength and compressive and flexural tests were performed on it. The obtained results were recorded as index Results. The following two types of metal fibers with consumption 0. 5% and 1% in unit volume and polymer fibers with the use of 0. 3 and 0. 6% in unit volume in the plans mixture was used this fiber to mix design base were added. Fibers made from blends of standard cylindrical samples with dimensions of 30 x 15 and 50 x 15 x 15 cm prismatic beam samples were made and after processing all the sample tests to determine the compressive strength, flexural and tensile were. The 28 days results indicate that the metal fibers to the RCC at a rate of 0. 5% and 1% respectively per unit volume increases the compressive strength of concrete roller 10. 1% and 13. 9% respectively and increases the tensile strength 29. 5% and 45% and increased bending strength up to the 40. 6% and 66. 5%. And with the addition of polymer fibers at a rate of 0. 3% and 0. 6% per unit volume increases the compressive strength of RCC by 5. 06% and 6. 32% and increase the tensile strength of the order of 21. 1% and 31% and increased the bending strength of the 29. 1% and 42. 7% lead.

In this paper, the effect of asphalt overlays, which were reinforced with geogrid, modified by sasobit and combination of them on rehabilitation of reflective cracking, is studied. The laboratory tests were conducted under dynamic loading in bending mode to investigate reflective cracking retardation compared to reference samples. The results illustrated that in a certain range of variables, temperature variations and sasobit percentages are the most effective parameters on fatigue life and other responses. Another effective variable was the type of interlayer in asphalt slabs. Furthermore, it has been found that the combination of samples (modified by sasobit, reinforced with geogrid and a 3cm sand asphalt layer) (1SP. G. SA & 2SP. G. SA) had a better performance such as improving fatigue life and reducing crack propagation in all loading and temperature conditions compared to the reference samples. Based on the image processing results, the process and shape of crack growth vary greatly at different temperatures. Generally, at low temperatures (20 ° C) and frequencies the cracks grow from bottom to top and the width of them get smaller. However, with increasing the temperature and loading frequency, the top down cracks are also observed, which is due to the reduced resistance of the asphalt resulting from the reduction of adhesion and the fastening between the aggregate and bitumen.

In this study, the effects of two typical commercial heavy airplanes, namely airbus AA380-800 and Boeing B747-400ER, on the potential of reflective crack propagation in composite pavement have been investigated. The axles of the airplanes were positioned at different longitudinal and transverse distances from the center of crack and the stress intensity factors, and tensile strain at the tip of crack in asphaltic layer were determined and compared. Modeling and analysis were performed using extended 3D finite elements method. The asphaltic layer was assumed to behave as a viscoelastic material and the underlying layers were assumed to be linear elastic. Results show that higher maximum stress intensity factor in mode 1 is generated under Boeing airplane loading than airbus, and those in mode 2 and 3, are higher for airbus than Boeing. Results also reveal that by moving the center of axles along the longitudinal joint, the maximum tensile strain at the tip of crack decreases, such that 42. 87% reduction for airbus and 23. 89% reduction for Boeing airplane is obtained, in comparison to the loading at the center. By moving the center of axles in transverse direction, the maximum tensile strain at the tip of crack increases by 26. 73 and 17. 93%, in comparison with the load at the center for airbus and Boeing airplane, respectively.

Overlaying the old pavement with new surfacing material is one of the commonly used methods for rehabilitating deteriorated pavements. The existing cracks in the old pavement propagate through the newly laid overlay and reach the free surface in due course of time. This phenomenon is referred to as reflection cracking. In general, using of stress absorbing membrane interlayer (SAMI) is one of the methods to control reflective ceacking. The main aim of this study is the evaluation of performance of SAMI in high stress level. The SAMIs in this study made by porous asphalt and Stone Mastic Asphalt (SMA) and paved between the old asphalt pavement and new surfacing layer. To do so, first test specimens made up of 2 and 3 layers which respectively were without and with SAMI. Afterwards to investigate the performance of SAMIs, dynamic creep test and specific fracture test by new geometry carried out. The fracture test able to simulate/model reflective growth in mixed modes I/III of fracture mechanism. The findings of study indicated that using this type of SAMIs reduce the fatigue life and cannot able to retard reflective cracking. Also, using SAMIs result in deformation increase.