Causes of Asphalt Pavement Distresses and their Remedies; A Case Study of Mekenajo-Nejo Asphalt Road; Ethiopia.

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