Abstract:
In recent years, the highway and construction industries have consumed an enormous amount
of conventional aggregate every year. The increasing demand for conventional aggregate
causes an increase in the cost of construction. In such instances, using of locally available
materials plays a significant role in the cost and time saving of road construction projects.
Hence, this research was initiated with the motivation of upgrading and utilizing the cinder
gravel, which is one of the abundantly available low-cost materials in the main rift valley of
Ethiopia. Besides, in some regional parts of Ethiopia, there is a scarcity of good base course
materials. Using these materials everywhere incurs transportation cost and is time consuming. Therefore, this study has been carried out in order to investigate the performance
of mechanically blended natural cinder gravels to be used as a road base course material
and to provide an alternative material for road construction. An attempt has been made in
this study to evaluate the potential use of cinder gravel as a base course material when
blended with fine crushed rock aggregate. To achieve the objectives of the research,
mechanical stabilization and laboratory tests have been carried out at different percentages
of cinder gravel by (0%, 15%, 20%, 25%, and 30%) of fine crushed rock weights. The
laboratory test results for cinder gravel indicated Los Angeles abrasion value (LAA), specific
gravity (SG), aggregate crushing value (ACV), and aggregate impact value (AIV). Plastic
Index, Water Absorption, and California Bearing Ratio (CBR) of 42.7, 2.4, 45.7%, 32.4%,
non-plastic, 8.83%, and 65.54%, respectively. These test results failed the ERA standard
specification for some tests, and they showed marginal quality values for the standard
specification for GB2 and GB3 base course materials. Thus, mechanical stabilization was
done to improve the mechanical and physical properties of cinder gravel. Blending of 75%
cinder gravel with 25% CFA results in LAA, SG, ACV, AIV, Plastic Index, Water Absorption,
and CBR of 35.7%, 2.7, 28.1%, 27.98%, non-plastic, 1.16%, and 125%, respectively. At this
proportion, the gradation is also observed to fit with the required ERA standard specification
of GB2 and GB3 materials. Therefore, it can be concluded that the use of cinder gravel up to
75% by weight is recommended for the road base course layer in places where the materials
are abundantly available
