THEPOTENTIALUSEOFCINDERGRAVELASABASECOURSE MATERIALWHENBLENDEDWITHRAPANDCRUSHEDSTONE AGGREGATE

Abstract

In Ethiopia, large quantities of cinder gravels are available, most of which are not utilized. This study investigates blending of cinder gravel with reclaimed aggregate and crushed stone aggregate in construction of base course layer. In this regard, the investigation of blending natural cinder gravel and reclaimed asphalt pavement by stabilization technique was conducted for samples collected from Butajira area. In the first phase of investigation, laboratory tests carried out to check the suitability of individual material samples of CG, RAP and CSA. In the second phase of investigation, mechanical and physical stabilization was carried out at 10%,20%,30% and 40% of CG blended with RAP in order to determine the more appropriate amount of mix ratio of CG to RAP that helps to get maximum replacement amount of CSA. In this method, the mix ratio of CG to RAP that has more appropriate properties of base course material according to ERA specification has been found to be 30%CG and 70% RAP by weight. In the third phase of investigation, mechanical and physical stabilization was carried out at 30%, 40%, 50% and 60% of CSA were blended with the blend of CG and RAP in order to find the optimum amount of CG and RAP by weight that replaced by the blend of CSA. In this case, as the amount of the blend of (CG-RAP) increases from 40%-70% the test results of ACV, LAA and water absorption increase from (12.48%-17.14%) , (4.46%-9.87%) and (0.93%-2.78%) respectively, the test result of CBR and specific gravity decreases from (94.4%- 53.4%) and (2.780%-2.47%) respectively. According the test results, all the mix ratio by weight of blend material value of ACV and LAA satisfies the ERA specification recommendation for base course materials, ACV<25% and LAA< 35%. In-case of CBR, specific gravity and water absorption the amount by weight of 50%CSA are respectively 83.2, 2.58 and 1.57 which satisfies the ERA base course specification, CBR>80%, SG= 2.50-3.0 and water absorption <2%. The gradation of blended material of 50%CSA to 50%(CG-RAP) blend is also within the upper and lower limit of ERA recommendation of base course material. The results obtained from Gradation, SG and water absorption, ACV, LAA, Compaction and CBR indicate that mixes containing 50% (CG–RAP) contents were successfully replaced CSA in highly trafficked unbound road base course layer of Asphalt concretes. Therefore, it is recommended to use the CG and RAP material for road construction project in places where in abundant of both materials are available