Blending of Volcanic Cinder and Natural Gravel for Sub-Base Road Construction, a Case Study of Gelan Asphalt Project, Addis Ababa, Ethiopia

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Addis Ababa University


Pavement design is aimed for achieving a pavement structure which is economical, comfortable and yet safe to travel by motorist; and which minimizes development of pavement distress features during the design life of the pavement. However, inappropriate selection of road materials for construction may cause early pavement failure. Low quality or out-of-specification materials are usually available from local sources. If there is appropriate treatment of the materials or/and structural design, the optimum use of local materials can be permitted, the construction can be accelerated and significant monetary benefits can be realized.Acccordingly in this study it was attempted to define the requirement related to blending of some volcanic cinder gravel from south east of Addis Ababa for Gelan Asphalt road project. The performance of mechanically blended volcanic cinder with natural gravel was evaluated in meeting Ethiopian Road Authority (ERA) manual specification. The cinder gravel was blended with some trial proportions of 1:1, 2:1 and 3:2 weathered natural gravel by mass and different test including grain size distribution, Attereber limit, California Bearing ratio Linear shrinkage, Loss Angeles Abrasion and perographic analysis has been conducted. Results showed that blending of 50% of natural gravel with 50% volcanic cinder, and 67% natural gravel with 33% of volcanic cinder has no plasticity characteristic and its plastic product is zero. However blending of 60% of weathered natural gravel with 40% of volcanic cinder improves its index properties and readily can be used for sub-base road construction as far as it satisfies ERA sub-base materials requirements.



Blending, Volcanic Cinder, Natural Gravel, Sub-Base Road Construction, Case Study, Gelan Asphalt Project, Addis Ababa, Ethiopia