Fiber Reinforced White Topping as a Rehabilitation Alternative over Flexible Pavement: An Experimental Study on Awash-Mille Road
Résumé
Abstract White topping is a rehabilitation treatment on asphalt concrete. This is one of the rehabilitation method believed by many researchers to lower maintenance cost of the pavement with very good performance result. It is increasing both in developed and developing countries; but the concept is new and have not been applicable in Ethiopia. In Ethiopia, asphalt overlay is the dominant type of rehabilitation measure to restore bituminous pavement distresses. Ethiopian Roads Authority (ERA) is currently maintaining the road from Awash to Mille which had experienced rutting, fatigue and thermal cracking. The road was designed for critical period of 5 years for rehabilitation with overlay thickness ranging from 50 mm to 120 mm. Some of the section experienced rutting and fatigue cracking within 1 to 2 years after it had been constructed. The research study utilized experimental evaluation to achieve the objectives on 1 km length of the selected segment. Field testing was carried out using Benkelman Beam Deflection equipment to assess the structural situation of existing asphalt. The deflection & modulus of sub grade reaction result indicates that the severity of the rutting would not be associated to the overall strength of the roadway as indicated by its very low deflection. Laboratory testing was accomplished to determine the optimum plastic percentage mixed in the concrete as fiber reinforcement. The result indicates that adding of shredded plastic with plastic fiber of 0.25% weight of cement improves both compressive and tensile strength of concrete. The 28th day for compressive strength and split tensile strength was increased by 1.08% and 5.53% respectively. Therefore, adding amount of 1.063 kg per m3 in white topping improved shrinkage and cracking which is the drawback of normal concrete. Using input from field and laboratory test result white topping thickness had been designed using Bonded Concrete Overlay of asphalt Mechanistic-Empirical design tool as rehabilitation alternative for the deteriorated flexible pavements. Finally, an attempt was made to compare initial construction cost of Fiber reinforced white topping with that of conventional flexible overlay designed by ERA. From the assessment of the study, early construction cost of white topping with 127 mm thickness was greater in 872368.8 ETB than 55 mm thickness of asphalt overlay designed by ERA. Therefore, it is necessary to construct a few trial section using local materials, traffic and climatic conditions to check its performances.
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