Investigation on Characterization and Partial Replacement of Recycled Asphalt Pavement with Virgin Crushed Aggregate and Volcanic Ash Filler as Un Bound Base Course Material (Case of Addis – Adama Express Way)

Abstract

Ecycling Asphalt Pavement Has Become A Common Practice In Road Construction Due To Environmental Benefit Such As Preservation Of Natural Material, Reduction Of Carbon Emission And Energy Saving In The Processing And Haulage Of Crushed Standard Aggregate(CSA), Reduction Of Disposal Of Recycled Asphalt Pavement (RAP) And Landfill. In Addition, Use Of RAP Has Economic Benefit Due To Reduction Of Material Cost And Haulage And Time Saving. Furthermore, Its Use Fits With Global Objective Of Sustainable Development. Nevertheless, Their Use In Ethiopia For Road Construction Is Unfamiliar And Waste At Fill Area Or Disposes On The Shoulder Creating Disposal And Environmental Problem. This Research Aims To Partially Replace Crushed Standard Aggregate With Recycled Asphalt Pavement As Un Bound Base Course Material For Heavily Trafficked Road. The First Phase Of This Study Consists Of Conducting Laboratory Tests On RAP And CSA Collected From Addis-Adama Expressway At South Bishoftu Entrance And ICT Park Stoke Pile Respectively. Whereas, The Second Phase Comprises Of Testing CSA- RAP Blend At Replacement Percentage Of 20, 30 And 40 RAP By Total Mass Aggregate And Addition Of 4% Volcanic Ash Filler. The Laboratory Test Performed Were Gradation, California Bearing Ratio (C.B.R), Modified Procter, Aggregate Impact Value, Aggregate Crushing Value, Ten Percent ?Fines Value, Flakiness Index, Loss Angles Abrasion Value, Specific Gravity And Water Absorption Tests. The Test Results Of RAP Aggregate Shows Value Of LAA 27%, AIV 17%, ACV 16%, TFV 227KN, Flakiness Index 29% And Non-Plastic Which Satisfies ERA Specification For GB1. However, RAP Having Particle Size Distribution Of Gap Grade, Lower Maximum Dry Density Of 1.918g /Cc And Lower CBR Value Of 14%, RAP Does Not Qualify Criteria Of GB1. Except CBR Test At 40% RAP Content, All Laboratory Test Results Conducted On All CSA-RAP Blend Samples Satisfy The Requirement Of ERA Of GB1 Material. Therefore, For The Studied CSA And RAP Material, Replacing CSA With RAP Up To 30% By Total Mass Of Aggregate And 4% Volcanic Ash Filler Satisfy Bearing Capacity Specification Measured By CBR Test Having CBR Value Of 100%. Finally, The Researcher Concludes That It Is Possible To Replace CSA With RAP Up To 30% By Total Mass Of Aggregate For Un Bound Base Course Material For Heavily Trafficked Road And Recommends The Variability Of RAP Material, Performance Of CSA And Volcanic Ash Filler Amount Should Be Determined Before Use As GB1 Material.