Characterization of recycled asphalt pavement (RAP) for use in flexible pavement

Abstract

Due to economical reasons and the need for environmental conservatism, there has been an increasing shift towards the use of Recycled Asphalt Pavement (RAP) materials in the pavement construction industry. The majority of HMA mixtures in Egypt are produced only from virgin materials although there are about 4 million tons per year of reclaimed asphalt materials, due to continuous pavement milling or scraping processes, are not used. High durability potential usually implies that the mechanical behavior of the mixture will endure for a long service life. Now, flexible pavement, made of Hot-Mix Asphalt (HMA) with the addition of the reclaimed asphalt pavement granules in the central asphalt mixing plant, is increasingly used. The main objective of this paper is to investigate the use of a homogeneity reclaimed asphalt pavement in the pavement industry evaluating the effects of partial and total replacements of aggregates by RAP on the mechanical and durability performance of dense-graded HMA mixtures. The performance of RAP mixtures was evaluated through a series of laboratory tests including Marshall test, indirect tensile strength test, granule adhesion test and material test systems. A series of binder mixes containing varying percentages of RAP were designed and subjected to different moisture conditioning periods (1, 3 and 7 days) to investigate the moisture damage effect on RAP mixtures. The laboratory results indicated that when properly designed, the asphalt mixes with RAP especially at 50 to 100% replacement ratio provided better performance compared to those of new conventional HMA mixtures where they minimized the environmental impacts through the reduction of energy consumption, improved the mechanical properties, durability performance and also stripping resistance.