Abstract
The use of recycled aggregates, manufactured from several by-products, to replace virgin aggregates in the production of pavement asphalt mixtures needs to be encouraged. Nevertheless, there are some concerns and uncertainties about the actual environmental, economic and mechanical performance resulting from the incorporation of recycled aggregates in asphalt mixtures. Therefore, this paper has the goal of discussing important features to help decision makers to select recycled aggregates as raw materials for asphalt mixtures. Based on the literature review carried out and the own previous experience of the authors, the article’s main findings reveal that incorporating some of the most common recycled aggregates into asphalt mixtures is feasible, even in a life-cycle analysis perspective. Although some specific technical operations are sometimes necessary when using recycled aggregates in asphalt mixtures, some benefits in terms of environmental impacts, energy use and costs are likely to be achieved, as well as in what concerns the mechanical performance of the asphalt mixtures.
Highlights
The activities of constructing and maintain highways’ pavements have a contribution to the footprint of transportation sector
Because this refining process is related to the energy sector, the footprint issues associated to bitumen have had generally more attention than the concerns related with the aggregates and, several solutions have been proposed to reduce the environmental impact of its use [1,2,3,4]
Based on the American long-term pavement performance program (LTPP) database, which considers roughly 15 years of data records, the authors participated in a study to evaluate the influence of using RAP in asphalt mixtures on the evolution of pavement conditions, when the mixes are applied in pavements rehabilitation [85]
Summary
The activities of constructing and maintain highways’ pavements have a contribution to the footprint of transportation sector. These layers include different blends of aggregates (roughly 95% of weight), obtained by crushing rock extracted in quarries, and bitumen (about 5% of weight), produced in refineries as a by-product of distillation of crude oil, and, sometimes, additives to change some specific features of the asphalt mixtures [1,2,3] Because this refining process is related to the energy sector, the footprint issues associated to bitumen have had generally more attention than the concerns related with the aggregates and, several solutions have been proposed to reduce the environmental impact of its use [1,2,3,4]. This paper assesses the feasibility of using recycled aggregates as substitutes of natural aggregates to produce asphalt mixtures based on own experience and on a review of the main issues related to the use of recycled aggregates, focusing on the availability of the most common recycled aggregates for the Portuguese market, their properties and specific aspects of their production and use, the expected performance of asphalt mixtures using these recycled aggregates and the issues related to the potential benefits in terms of direct costs, emissions and energy consumption
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