Comparative Study of Flexible and Composite Pavement Structures (A Case Study on Addis Ababa - Djibouti Trunk Road Segment)

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Addis Ababa University


Most major road networks in Ethiopia constructed with flexible pavement, this type of pavement used as the only option considered during the pavement type selection (PTS) process for many years. Composite pavement, which is a combination of a rigid base overlaid with a hot-mix asphalt (HMA) surface course, is proposed to be considered as alternative during PTS process in this study. The thesis seeks to find out the better option between flexible and composite pavement in levels of performance both structurally (technical aspect) and economically viable alternative (economic aspect) over the analysis period of time for Addis Ababa - Djibouti trunk road segment. The thesis covers design of both flexible and composite pavement, technical analysis and computation of respective costs over an analysis period of 40 (forty) years. Appropriate input parameters used for empirical method of design, linear elastic analysis using Kenpave software and deterministic life cycle cost analysis (LCCA); and the output expressed with graphs and charts. The data required for this study was obtained from journals, design manual, books and reports of various organizations. Material and traffic data used to come up with the pavement design details which, gives respective pavement layers thickness and type of materials used for each layer. These design outputs ultimately used for pavement structures economical and structural comparison. A mechanistic analysis based on the multi-layer linear elastic theory was performed on different composite structures to understand the structural responses (stress, strain and deflection) and compared with flexible pavement. At the economic level, a deterministic LCCA was performed. Results from technical analysis of this study suggest that composite pavements have potential by mitigate various structural and functional problems that typical flexible pavement tend to present, such as HMA flexural fatigue failure, HMA rutting due to subgrade vertical deformations. The results of the deterministic LCCA suggest that the use of a composite pavement results in cost-effective alternative than flexible pavement. So, composite pavements have structural and economic potential to be considered during the pavement type selection process for major roads.



Pavement Structures, Addis Ababa - Djibouti Trunk Road Segment, flexible pavement, Composite Pavement