الفهرس 
INTRODUCTION & OBJECTIVESOnly 14 pages are availabe for public view
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Abstract
The asphaltic layers after construction are exposed to many problems e.g. “reflection cracking”. This type of distress causes the cracks to reflect from the bottom layers of pavement to the upper surface that leads to a decrease in the level of service and lifetime of pavements. In order to improve rehabilitation costs and increase pavement service life advanced technical solutions have been established. One of the most widespread techniques introduced for this scope is using geogrids at the interface between different layers of pavement structures. Geogrids provide different performance depending on their characteristics, such as constituent materials, surface coating, mesh geometry and dimensions, and on their position in the pavement structure.The main objectives of the research are to study the effectiveness of varying the thickness of binder layer and two types of geogrid were used (biaxial and triaxial). There were 27 model specimens divided into three groups according to binder layer thickness. The specimens are tested to investigate the effect maximum load and deformation values moreover the flexural stresses and flexural stiffness. Shearing properties are also studied >and the cost effectiveness of using geogrid in asphalt layers.Test results showed that geogrid reinforcement specimens had less deformation and sustained higher failure load when compared to the unreinforced specimens for both geogrid types and for all pavement thicknesses. Triaxial geogrids out-performed biaxial geogrids, where the average failure load for specimens reinforced with triaxial geogrids with thickness 90 mm were comparable to specimens reinforced with biaxial geogrid with thickness 100 mm, with slightly increase in deformation value. This can allow for a reduction of the binder layer thickness in case of using triaxial geogrid reinforcement.Test results showed that in unreinforced specimens, the crack proceed from binder layer to surface layer on contract, the surface layer in both biaxial geogrid reinforcement and triaxial geogrid reinforcement not affected by crack. According to the economic study,which is based on local conditions, there is an increase in cost associated with introducing geogrids in asphaltic layers. This added cost maybe offset by longer life and reduced maintenance