الفهرس 
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Abstract
Asphalt concrete pavements experience damage due to the increase of traffic
volume and more importantly the repeated traffic loads. Environmental conditions
such as temperature, aging, and water can have a significant effect on the
performance of asphalt concrete pavements as well. Bitumen is a visco-elastic
material where temperature and rate of load application have a great influence on
its behavior. Conventional bitumen is exposed to a wide range of loading and
weather conditions; it is soft in a hot environment and brittle in cold weather.
Rutting (permanent deformation), fatigue cracking, and moisture damage are the
most common distresses that can be found in Egyptian roads. Those distresses can
have negative impacts on roadway safety, reduce the service life of the pavement
and increase the maintenance cost.
On the other side, disposal of waste tires has been acknowledged to be
a serious environmental problem. Also burying tires in landfills is not an easy
solution either. So improvement of asphalt concrete mixtures by adding Crumb
Rubber (CR) can be a possible solution to reduce these problems and preserves the
environment from pollution.
In this research an investigation was made on the fundamental studies of
modified asphalt binder and mixtures in order to understand the influence of
modifiers on the Mechanical properties and fatigue resistance to prevent fatigue
cracking in asphalt pavement. Crumb rubber modifier as a waste material is used in
modifying the performance of the asphalt concrete mixtures using wet process in
which the CRM is added to the base asphalt binder before introducing it in the
asphalt concrete mixture. The conventional bitumen (60/70) penetration grade was
used in this research, modified with crumb rubber modifier (CRM) at three
different contents namely 7%, 10% and 13% (by weight of the bitumen).Mechanistic and simulative tests namely Standard Penetration test, Softening Point
test, Indirect Tensile Strength, Critical Energy Release Rate, Marshall Stiffness,
Static Creep test and Compression test were conducted in this research.
The results of the study indicated that, the addition of Crumb Rubber generally
improved the mechanical properties of the mixture regardless of the percentage of
the Crumb Rubber. The addition of crumb rubber modifier by 10% (by weight of
the asphalt cement in the mix) was the optimum content of CRM to achieve the
best improvement for the modified mixtures properties. Also, the addition of the
CRM causes a significant improvement in fatigue resistance and the permanent
deformation resistance.