Characterization of Reclaimed Asphalt Pavement (RAP) for Use in Bituminous Road Construction

Abstract

A good road network is a critical infrastructure requirement for rapid economic growth. It provides connectivity to remote areas; provides accessibility to markets, schools, and hospitals; and opens up backward regions to trade and investment. Roads play an important role in inter-modal transport development, through links with airports, railway stations, and ports. Road network in India aggregates to about 4.2 million kilometers. This extensive road network, the second largest in the world only after US, caters to about 65 per cent of the freight traffic and 87 per cent of the passenger traffic. National Highways (NH) constitute about 70,934 kilometers which is only 2 percent of the total network. However, it caters to nearly 40% of the total road traffic. State Highways (SH) and Major District Roads (MDR) together constitute the secondary system of road transportation which contributes significantly to the development of the rural economy and industrial growth of the country. The conventional method of providing bituminous surfacing on flexible pavements require significant amount of energy for production of bituminous binder from crude petroleum, drying aggregates and subsequently production of bituminous mix at hot mix plant (HMP).Hot mix recycling is the process in which reclaimed asphalt pavement materials are combined with new materials, sometimes along with a recycling agent, to produce hot mix asphalt mixtures. When properly designed, recycled mixtures can have better or similar performance to those of new conventional hot mix asphalt mixtures.Recycling or Rejuvenating agents have been defined as organic materials with chemical and physical characteristics selected to restore properties of aged asphalt to desired specifications. In selecting the recycling agent, the viscosity characteristics of the combined aged asphalt binder and the recycling agent are the determining factors. These agents are also known as softening agents, reclaiming agents, modifiers, fluxing oils, extender oils, and aromatic oils. The choice of Recycling Agent (RA) grade will depend on the amount and hardness of the asphalt in the aged pavement. In general, the lower viscosity RA types can be used to restore aged asphalts of high viscosity and vice versa. Laboratory studies have been carried out on asphalt mixes with RAP material and rejuvenating agent and their performance has been compared with virgin asphalt mixes. Various performance tests such as Retained Stability, Indirect Tensile Strength (ITS), Creep test, beam fatigue test, resilient modulus and wheel tracking test has been carried out to compare the performance properties. This paper presents the results of all such performance tests carried out on asphalt mixes with RAP and virgin mixes. The laboratory results indicate that the asphalt mixes with RAP and rejuvenating agent provide better performance compared to virgin mixes. The paper also recommends that the Accelerated Pavement Testing Facility (APTF) should be put to use to evaluate the actual field performance of recycled pavements in a faster and effective manner.