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Most of the researches indicated that reasons for the emergence of such defects and damage can be for technical reasons, geometric, or operational or administrative errors.
Which can be summarized as follows OECO, 2008 :
a.
Engineering or technical reasons
The body of the road can summery it because of the failure of terminate is surface of the pavement may be good or bad mix asphalt, it may defect in the base or
subbase layers.
b.
Operational reasons
The method used in the road which negligence by the users of the road may impact on the pavement.
c.
Management reasons
These defects in the selection of the contractor or supervising engineering the construction of road. When the contractor does not have sufficient experience. It is
difficult to do this job.
2.2 Deterioration in Flexible Pavement
Assessment of the pavement condition is by the visual observation and recording of types of defects on the surface of the pavement.Pavement condition survey includes
detection of surface distresses, such as cracking, rutting, and other surface defects, and can also include survey of pavement roughness in certain cases.
The elements of visual assessment of the situation as follows:
a. Type of distress.
b. Severity of distress.
c. The intensity of the impact of defect layer pavement.
Before any inspection of the site must follow the safety means so as to ensure the safety and conduct of the examination process.
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This manual is prepared to assist user of the Pavement Management System PMS
in identifying surface distress in a uniform and repeatable manner. The distresses included
in this manual are used to calculate the Pavement Condition Index PCI for pavements
surfaced with asphalt concrete and surface treatments. This part contains general descriptions of the major types of distress that may be
encountered in both flexible asphalt concrete and rigid pavements. Also noted is a typical description of three distress severity levels associated with each distress.
A pavement moisture accelerated distress identification system. These descriptions are provided as a guide to user agencies only and should not be viewed as a standard
method for distress type severity identification. This information, along with an estimate of the amount of each distress severity combination, represents an example of the minimum
information needs required for a thorough condition distress surveyAASHTO, 1993.
2.3 Pavement Distress
Pavement distresses are those defects visible on the pavement surface. They are symptoms, indicating some problem or phenomenon of pavement deterioration such as
cracks, patches and ruts. The type and severity of distress a pavement has can provide great insight into what its future maintenance andor rehabilitation needs will be. The distress is
generally described in terms of severity, extent and distress type. However, the distress identification and measurement procedures may slightly vary from agency to agency
Luo,2005. Defects in the asphalt pavement can be classified groups on the basis of
appearance as follows David, 2006:
2.3.1 Cracks
2.3.1.1 Alligator or Fatigue Cracking a.
Description
Alligator cracking is a series of interconnecting cracks caused by fatigue failure of the asphalt concrete surface under repeated traffic loading .cracking
begins at the bottom of the asphalt surface or stabilized base where tensile stress and strain are highest under a wheel load. The cracks propagate to the surface
initially as a series of parallel longitudinal cracks. After repeated traffic loading, the
