Types of Failure in Flexible Pavements: A Case Study of the Ethiopian Federal Road Network

Pavement is the hard-wearing surface built over the natural (subgrade) soil to provide a strong, stable, and smooth riding surface. A typical section of flexible pavement comprises a surface course, base course, and sub-base and subgrade layers. These layers are structured based on their load-bearing capacity (strength), with the strongest and most expensive layer at the top, and the weakest and least expensive at the bottom. However, due to several reasons attributed to the environment, traffic volume and load, subgrade condition, pavement age, construction quality control and assurance, and composition and properties of the construction and maintenance materials, asphalt pavements do not perform as expected. Accordingly, identifying the failure types is critical in understanding the contributing factors and proposing appropriate remedies. In Ethiopia, although there have been some efforts to identify pavement failure types on individual projects, no comprehensive study has been conducted to assess asphalt pavement failure types at a national or regional level. Therefore, the objective of this study was to identify the predominant Flexible pavement failure types in Ethiopia's high-traffic roads with a focus on Trunk, Link, and Main Access Roads. Self-administered close-ended questionnaire was developed and distributed to eighteen Ethiopian Roads Administration Roads Network and Safety Management Branch Office Directors and Maintenance District Directors. The questionnaire responses were analyzed using Statistical Package for the Social Sciences (SPSS) software and the relative importance index (RII). The finding showed that the primary road failure types in the Trunk, Link, and Main Access Road networks are potholes, rutting, fatigue cracking, shoving, patch deterioration, and edge break.