Pavement Distresses on Addis Ababa City Arterial Roads, Causes and Maintenance Options
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Date
2005-04
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Addis Ababa University
Abstract
Paved roads in tropical and sub tropical climates often deteriorate in different ways to
those in temperate regions, because of the harsh climatic conditions, lack of proper
design and quality control, high loads and inadequate assessment for identifying
causes of distresses before carrying out maintenance and rehabilitation.
A pavement distress that occurs at the surface can have a number of different causes
which must be properly identified before corrective action is taken. The visible
manifestation of the problem at the surface may be the same; however, the solution
for each cause may be different. Therefore, if the remedial action is to be effective, the
cause of the problem must be identified and corrected.
The present road condition of Addis Ababa shows rapid deterioration. The severity of
pavement distresses is even more critical on the major arterial roads were the traffic
volume of busses, heavy trucks, passenger vehicles and taxies is comparatively
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higher than other road network. Such severe distresses summed up with inadequate
road signs and markings are resulting congestion and consequently causing further
deterioration of roads due to maximum static load sustained from the vehicular traffic
waiting in a queue on the pavement.
This research mainly focuses on making assessment of asphalt pavement condition,
identifying causes of pavement distress and proposing maintenance options for the
arterial roads of Addis Ababa. These roads are most widely utilized, and therefore
prone to severe distress and consequently exhibiting repeated maintenance and
repair. Visual distress assessment, roughness tests, DCP tests and other necessary
laboratory investigations were carried out on selected test sections in order to have
better understanding of the pavement response and come up with identification of
probable causes. Major causes of pavement distress associated with load, drainage
and durability are tried to be identified.
A statistical analysis is also made to check how each investigation results showing
pavement response variables and material properties interact with each other to
identify the cause of distresses. The visual survey analysis indicates that almost all
test roads have very low PCI value. Raveling, corrugation, Bumps and sags are the
most dominant type of distresses constituting more than 75% of the distress densities
in the arterial road network. The majority of test sections showing low PCI values are
observed to have a base material of low bearing value sandwiched between the
asphalt and other pavement layers. The investigation and analysis also showed that
moisture and drainage associated distresses are predominant in the arterial roads and
most likely on the whole network as well. Moreover, it is also observed that most of the
existing pavements lack structural adequacy and hence require reconstruction than
doing a routine maintenance and/or rehabilitation.
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Keywords
Roads; Causes ; Maintenance