A Case Study of Industrial Symbiosis to Reduce GHG Emissions: Performance Analysis and LCA of Asphalt Concretes Made With RAP Aggregates and Steel Slags
Abstract:The concept of sustainability in the road construction sector is a complex issue because of the various steps that contribute to the production and release of greenhouse gas (GHG) emissions. Addressing this issue, the European Commission has put various policy initiatives in place to encourage the construction industry to adopt circular economy (CE) and industrial symbiosis (IS) principles e.g., the use of recycled materials. Cooperativa Trasporti Imola (CTI), a company located in the Emilia-Romagna region (It… Show more
“…In particular, the impact indicators IR, OFT and MR of CMRA RAPJGW are on average 12% lower than those of CMRA RAP due to the lower gaseous and particulate air emissions and minerals consumption required to produce the aggregates and cement (see Table 2b). The same results have been demonstrated by Bonoli et al [81], who showed that the recycling of RAP combined with steel slag aggregates provides benefits by reducing the consumption of virgin bitumen and aggregates and, at the same time, by reducing the CO 2 equivalent emissions.…”
The integration of circular economy principles in the design of road pavements raises the problem of obtaining high-performance asphalt mixtures for reduction of waste and environmental pollution compared to traditional solutions. In this study, the base and binder layers of road asphalt pavements were prepared by using reclaimed asphalt pavement and construction and demolition waste as coarse aggregates, while jet grouting waste and fly ash served as fillers. A leaching test was performed for the marginal materials, after which the engineering performances of the designed asphalt mixtures were investigated through laboratory tests. A life cycle assessment methodology was applied to determine the life cycle impacts of one cubic meter of each asphalt solution. Next, a multi-criteria decision analysis (MCDA) was performed for the solutions suggested for the binder and base layers. Finally, a sensitivity analysis was conducted to identify the most suitable MCDA solutions by varying the weights for a total of 24 different weight configurations. The results of this work revealed that the solutions utilizing jet grouting waste (in particular, the hot asphalt mixture for the binder layer and cold asphalt mixture for the base layer) were preferred to other traditional and alternative solutions in most decision-making scenarios.
“…In particular, the impact indicators IR, OFT and MR of CMRA RAPJGW are on average 12% lower than those of CMRA RAP due to the lower gaseous and particulate air emissions and minerals consumption required to produce the aggregates and cement (see Table 2b). The same results have been demonstrated by Bonoli et al [81], who showed that the recycling of RAP combined with steel slag aggregates provides benefits by reducing the consumption of virgin bitumen and aggregates and, at the same time, by reducing the CO 2 equivalent emissions.…”
The integration of circular economy principles in the design of road pavements raises the problem of obtaining high-performance asphalt mixtures for reduction of waste and environmental pollution compared to traditional solutions. In this study, the base and binder layers of road asphalt pavements were prepared by using reclaimed asphalt pavement and construction and demolition waste as coarse aggregates, while jet grouting waste and fly ash served as fillers. A leaching test was performed for the marginal materials, after which the engineering performances of the designed asphalt mixtures were investigated through laboratory tests. A life cycle assessment methodology was applied to determine the life cycle impacts of one cubic meter of each asphalt solution. Next, a multi-criteria decision analysis (MCDA) was performed for the solutions suggested for the binder and base layers. Finally, a sensitivity analysis was conducted to identify the most suitable MCDA solutions by varying the weights for a total of 24 different weight configurations. The results of this work revealed that the solutions utilizing jet grouting waste (in particular, the hot asphalt mixture for the binder layer and cold asphalt mixture for the base layer) were preferred to other traditional and alternative solutions in most decision-making scenarios.
“…Several steps contribute to the production of GHG, but the material extraction and production stage has been identified as the main contributor to total carbon emissions and energy consumption [12]. Hence, the choice of materials impacts local pollution and environmental degradation [13].…”
Blast Oxygen Furnace (BOF) slag represents one of the largest waste fractions from steelmaking. Therefore, slag valorisation technologies are of high importance regarding the use of slag as a secondary resource, both in the steel sector and in other sectors, such as the construction or cement industries. The main issue regarding the use of BOF slag is its volumetric instability in the presence of water; this hampers its use in sectors and requires a stabilisation pre-treatment. These treatments are also cost-inefficient and cause other environmental issues. This paper analyses the use of untreated BOF slag from a technical and environmental point of view, suggesting it as an alternative to natural aggregates in road surface layers and asphalt pavements. A comprehensive analysis of the requirements to be met by raw materials used in asphalt mixes was performed, and a pilot test was carried out with two different mixtures: one mix with limestone as coarse aggregate and another with 15% BOF slag. Furthermore, the global warming impacts derived from each mix with different aggregates were measured by Life Cycle Analysis (LCA), and a transport sensitivity analysis was also performed. The results show how the utilization of BOF slag as coarse aggregate in road construction improves the technical performance of asphalt mixtures (Marshall Quotient 4.9 vs. 6.6). Moreover, the introduction of BOF slag into the asphalt mix as a coarse aggregate, instead of limestone, causes a carbon emissions reduction rate of more than 14%.
“…The bottleneck is the difficulty of demonstrating the condition for by-products relating to the certainty of use (condition a) under the Waste Framework directive (WFD) article 5). In this context, industrial symbiosis initiatives at regional or national level, supported by a planning actions using MFA, will allow establish industrial symbiosis network among various companies in the road construction and rehabilitation sector [ 59 ] to achieve sustainable commercial opportunities for its members and to use resources efficiently. Fig.…”
A greater reuse of steel slags would bring considerable benefits both from an environmental and economic point of view. The development of tools and strategies to monitor at different scales resources and waste flows would allow for better resource planning and a more sustainable management on territory. The aim of this study is to investigate and analyse the supply chain that deals with the management of steel slags at meso-level, in order to investigate the state of implementation of industrial symbiosis (IS), its potential and its improvement. A Mass Flow Analysis (MFA) has been implemented, through big data analysis coming from the integration of regional and provincial databases with a careful data processing from questionnaires. This integrated methodology has proved to be a valid tool to monitor the recovery and reuse, the implementation of industrial symbiosis and to plan improvement actions. This paper reports a representation of the current situation regarding the production, recovery and reuse of these materials in production processes for which they are suitable, with a view to their full exploitation, following the principles of circular economy and an analysis of the mutual exchange that occur among steelmaking plants and other business partners in a network of industrial companies. The results showed that most of the steel slags managed at meso-level (Province of Brescia, Italy) is still unfortunately destined for landfill with low percentage of them classified as by-product highlighting as the IS is not adequately applied. Of the slag destined for treatments and recovery processes, almost all of them are Electric Arc Furnace slag, which are mainly reused for hydraulically bound base layers and road sub-bases (about 85% of the total recovered) and as aggregates for the production of cement and bituminous mixes (about 15% of the total recovered). Results shows as further effort should be made in term of policies and strategies to incentivize IS and to increase the recovery.
Graphical abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
