Abstract:
This study has been conducted on Mekenajo-Nejo Road segment which is located in
west Wollega zone of Oromiya regional state to identify causes of pavement distresses
and to recommend remedial measures. A pavement distresses that occurs at the
surface can have a number of different causes which must be properly identified
before corrective action is taken. The objective of this study is to examine the causes
and remedial measures for asphalt pavement distresses. It is also intended to compare
the engineering properties of the existing pavement layers with the standards and
finally, recommendations on how to address possible problems associated with the
different types of pavement distresses and deterioration. This research mainly focus
on making assessment of asphalt pavement condition, identifying causes of pavement
distresses and proposing remedial measures for the Mekenajo-Nejo roads in west
Wollega. Visual distress assessment, 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. During condition surveying some localized pavement distresses like potholes,
alligator cracks, raveling, Corrugation, rutting and poor drainage condition was
observed. The average thickness of each layers were measured and Asphalt 3.9cm,
Base 14.5cm, and Sub-base 18.0cm. From field investigation and laboratory test
result, the AASHTO and Unified Soil Classification are Subgrade A-7 and SC, subbase A-2-4 and GP and base course A-1-a and GW. Average liquid limit (LL), and
plasticity index(PI) in percent were base course (5,5), sub-base(23,7) and subgrade(47,15) and compaction, MDD(g/cc) and OMC(%), base course(1.86,6.63), sub
base(1.81,8.26) and sub-grade(1.64,17.77), CBR% were base course 94%, sub-base
86% and sub-grade14% obtained. Based on the laboratory test result and condition
survey the following are cause of pavement damages; Subgrade soil, degree of
compaction, improper pavement layer thickness, and Poor drainage. Finally surface
treatments, Fill cracks with asphalt emulsion slurry, full- depth patching, and
removing vegetation close to the ditches are some of the recommendation forwarded
