Recycling of asphalt pavements in new bituminous mixes

The recycling of Recycled Asphalt Pavement (RAP) in the production of new bituminous mixtures is an interesting possibility at a time when waste minimisation is to the fore. The economic cost of dumping RAP and other waste materials has increased which has led the drive by local authorities and contractors to investigate the recovery of RAP and other materials to reduce their spiralling waste disposal costs. The environmental effects of disposing RAP have posed questions to be asked about the pollution caused to the ground and streams by the leaking of leaches from RAP. The present investigation consisted of experimental and theoretical studies of using various % of RAP aggregate in three different mixtures. The aggregates used have been recycled from bituminous mixtures. The grading of the RAP material was firstly examined and the mix design was altered to produce specimens of the same composition as the base mixtures. Bituminous specimens and slabs were produced and stiffness, fatigue, tensile strength, Marshall, cantabro and wheel tracker tests were carried. The results showed that RAP could success fully be used in bituminous mixtures. The effects of the increased stiffness as a result of adding the various amounts of RAP aggregate were calculated using the Shell Pavement Design Manual 3.0 (SPDM). The results showed that using RAP aggregate in the production of bituminous mixtures could reduce the overall thickness of the pavement. Savings as a result of using RAP aggregate in bituminous mixtures were calculated and were offset against the cost of modifying the existing plant. From the results obtained the use of recycled materials in bituminous mixtures is economically viable. There are also financial benefits as a result of the reduced pavement thickness as calculated using SPDM 3.0. Since the completion of this project Roadstone Dublin have started to use RAP in the production of bituminous mixtures. A number of trials have been planned in conjunction with Offaly County Council for the summer of 2005.