Alemayehu, Ambo (PhD)Tasebe, Fisha2020-02-292023-11-112020-02-292023-11-112019-09http://etd.aau.edu.et/handle/12345678/20780The motive to conduct this study was initiated from repeated observations of excessive wastes of asphalt surface and road maintenance techniques in Addis Ababa. The study was focused on determining the materials property of recycled granular materials containing different percentages of recycled asphalt pavement (RAP) to use as an unbound base course material. Laboratory tests and field implementation were carried out to determine the physical and mechanical properties of virgin aggregates and various aggregate-RAP blends at different percentages. The results were used to evaluate the strength of granular layer for pavement construction through proper compaction and control of RAP usage. The tests were also conducted to check the standards and requirements specified by the Addis Ababa City Roads Authority (AACRA) and Ethiopian Roads Authority (ERA) using the procedures of the American Association of State Highway and Transportation Officials (AASHTO) testing manual. The sieve analysis test results showed that gradation of material RAP 1 and RAP 2 are better than the virgin aggregate gradation currently used by AACRA. Both standard and modified proctor compaction tests were carried out to evaluate the effect of variable compaction; the results also showed that the dry density of materials resulted from standard compaction is lower than the result in modified compaction of the same material. The laboratory CBR results showed that the blends with high content of virgin aggregate achieved high bearing capacities. Low CBR values was achieved by neat RAP materials of 100% RAP 1 and 100% RAP 2 materials. The blends containing 75% VA in all material types resulted in higher CBR values. RAP materials implemented in field as an unbound base course material for trial did not show any of early pavement distresses in one year service time. Beyond determining materials property the study review and asses current material production and road maintenance activity to consider major economic and environmental benefits emanated from using the recycled materials instead of virgin aggregate productions. In this regard, the economic benefits by using RAPs resulted in 50% saving of virgin aggregate production costs annually. In addition to economic benefits, reuse of RAPs may reduce road construction wastes generated from road maintenance and rehabilitation activity by 23% which is needless for the city, Addis Ababa.en-USRecycled Asphalt Pavement (RAP)CBRproctor compactionaggregate blendsThesis