Evaluation of Cinder Gravel for Gravel Road Surfacing Construction: A Case of Gadab Asasa Woreda

Abstract

Ethiopia has one of the lowest road densities and lowest Rural Accessibility Indexes in Sub- Saharan Africa (World Bank, 2016). The second Growth and Transportation Plan Of the country involves the construction of 100,000 km of road between 2015 and 2020, and it is likely that this planned expansion of the road network will continue in later years and decades. Cinder gravel offers significant potential as a low-cost, naturally occurring material in low-volume rural road construction and rehabilitation. However, the variability in its engineering parameters, particularly its grading, density, porosity and strength, have meant that the material often fails to meet standard specifications for road construction. From previous related studies, the sub-base and base courses such as cement, lime, calcium, fly ash were stabilized by so many researchers with mixing, but less attention was given to naturaly available Cinder gravel with fine materials for surfacing gravel road. The objective of this study is to investigate the strength characteristics of mechanically stabilized and to evaluate the potential use of cindergravel to be used as a surfacing gravel road material. when blended with fine grained soil. The samples of material were taken from Sigalo and Dabara Quarry sites.by using Experimental trial through processes of mixed, to achieve the ERA manual specification, the cinder gravel was blended with 0, 5, 10, 15, 20, and 25% of fine-grained soil by total mass. In this study the conducted tests includes gradation, compaction test, atterberg limits, specific gravity, AIV, ACV, LAA, and California Bearing Ratio test. Results indicated that the CBR, SG, AIV, ACV, LAA, water absorption and Atterberg’s limits of neat Cinder gravel are: 64%, 2.55, 39.87%, 41.63%, 43.36%, 13.3% No Value, respectively. The optimum amount of fine grained soil is 20 % by weight proportion at a density of 1.683 g/cc, the range of soaked CBR of the blended mix increases from 64 % to 85.9 % and PI value changed from zero % to 12.1%. Analysis of the results shows the addition of fine increase the plasticity index, CBR.MDD and reduce water absorption with an increase in MDD and CBR with steeped locally fine contents up to 20%. Therefore, it is concluded that, from both MDD and CBR-percent of fine-grained soil curve, the optimum amount of fine- soil treatment by 20%, as exhibited in improvement of its gradation and plasticity. From this study it was found out that locally fine soil stabilized with cinder gravel do meet the minimum requirement of ERA pavement manual specification for use as a wearing course material in gravel road construction