الفهرس 
thermal fatigue cracks especially in the northern and middle regions of theOnly 14 pages are availabe for public view
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Abstract
Thermal fatigue cracking is one of the major distress modes in Egypt
because of the significant variation in temperature between day and night
(during the day) or between summer and winter (during the year) in many
regions of the country. This type of distress is manifested as a series of
transverse cracks that extend across the pavement surface in response to
multiple cycles of temperature change. With increasing use of asphalt
concrete mix ”Type 4B” in Egypt as an alternative to the asphalt concrete
mix ”Type 4C”, it is essential to compare between the performance of
these two mixes under different environmental conditions. The main
objective of this study is to compare between the above mentioned two
mixes in resisting thermal fatigue cracking under the Egyptian conditions.
In order to achieve this purpose, a refrigerating-warming unit was
fabricated. Through this unit asphalt concrete specimens can be exposed
to different temperatures; maximum + 110°C minimum -20°e. Asphalt
mixture specimens were prepared for both mixtures (4B, 4C) using three
different percentages of bitumen (Marshall optimum percent. Marshall
optimum percent + 0.5%, Marshall optimum percent - 0.5%) to study the
effect of bitumen content on the resistance of thermal stresses. The
specimens were tested under three di fferent temperature cycles
compatible with those actual in three main regions in Egypt (north
middle, and south). The deformation occurring in specimens due to the
temperature change was recorded and then the number of thermal cycles
that can be applied on each specimen before cracks initiation was
predicted.
The study concluded that mix 4C is better than mix 48 in resisting thermal fatigue cracks especially in the northern and middle regions of the
country, while both mixtures can be used without a significant effect on
the pavement service life in the southern region. The study also concluded
that increasing the bitumen content above the optimum determined by
Marshall testing procedures by 0.25% (the maximum allowable tolerance
according to the Egyptian code) leads to increasing the number of
temperature cycles that can be applied on both mixtures (48, 4C) before
crack initiation.