Abstract
Steel slag is a byproduct generated as waste during the steelmaking process and can be considered a cost-effective and environmentally acceptable alternative to replace natural aggregates. Using steel slag aggregates (SSA) to produce asphalt mixtures promotes sustainability and circular economy principles by using an industrial byproduct as a raw material. Thus, this work mainly aims to design more sustainable asphalt mixtures with high amounts of SSA that fit the circular economy expectations. This work developed two asphalt mixtures with SSA for surface (AC 14 surf) and binder/base (AC 20 bin/base) courses. Initially, the excellent wearing and polishing resistance of SSA and their good affinity with bitumen demonstrated the potential of this byproduct to be used in asphalt mixtures. Then, when analyzing the influence of using two different SSA incorporation rates (50% and a percentage close to 100%) in both asphalt mixtures, it was concluded that the use of SSA should be limited to 75% to avoid excessive air void contents and durability problems. The importance of considering the different particle densities of SSA and natural aggregates was highlighted during the mix design by defining a relationship between an effective and equivalent binder content. Finally, the mechanical performance of AC 14 and AC 20 with 75% SSA incorporation was compared to identical conventional mixtures produced with natural granite aggregates. The results obtained showed that the asphalt mixtures with 75% SSA have some workability problems due to the rough and porous surface of SSA. However, they present an excellent water sensitivity and permanent deformation resistance, surpassing the performance of the conventional asphalt mixtures.
Highlights
Circular economy (CE) is a concept promoted by the European Union and several governments individually, which can be defined as an economic model based on the natural cycle, aimed at efficiently using resources through waste minimization, long-term value retention, and reduction of primary resources use [1,2].According to Mantalovas and Di Mino [3], the road engineering industry moves towards more circular approaches
The results obtained in the Marshall method were analyzed to determine the optimum binder content (OBC), considering the binder contents resulting in the maximum bulk density and Marshall stability and the mean value of Va specified for each type of mixture
This work aims to develop more sustainable asphalt mixtures that fit within the circular economy objectives
Summary
Circular economy (CE) is a concept promoted by the European Union and several governments individually, which can be defined as an economic model based on the natural cycle, aimed at efficiently using resources through waste minimization, long-term value retention, and reduction of primary resources use [1,2]. According to Mantalovas and Di Mino [3], the road engineering industry moves towards more circular approaches. Some standard practices that various stakeholders, companies, asphalt contractors, and agencies are implementing, in line with the circular economy principles, include recycling reclaimed asphalt, extending the service life of their assets (preventive maintenance), and using wastes in asphalt pavements [4]. The road engineering industry’s transition to a circular business approach requires managing the resources, energy, and waste more efficiently and sustainably [5]. According to Plati [6], the pavement’s sustainability is highly based on the proper selection of materials.
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