Life Cycle Assessment of a Sustainable and Innovative Solution for Unpaved Rural Roads †
by
, , ,
Leonardo Urbano
1
,
Lucia Tsantilis
1,*
,
Pier Paolo Riviera
1,
Orazio Baglieri
1 and
Ezio Santagata
1,2 1
Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
2
Department of Civil and Architectural Engineering, Qatar University, Doha 2713, Qatar
*
Author to whom correspondence should be addressed.
†
Presented at the Second International Conference on Maintenance and Rehabilitation of Constructed Infrastructure Facilities, Honolulu, HI, USA, 16–19 August 2023.
Eng. Proc. 2023, 36(1), 12; https://doi.org/10.3390/engproc2023036012
Published: 30 June 2023
(This article belongs to the Proceedings of The Second International Conference on Maintenance and Rehabilitation of Constructed Infrastructure Facilities (MAIREINFRA2))
Abstract
:The use of recycled aggregates, including waste materials and by-products, has attracted increasing interest in the last decades as a sustainable and cost-effective solution for the construction and maintenance of road pavements, due to the reduction of excavation operations and depletion of natural resources. Life cycle assessment (LCA) represents a valuable methodology for the evaluation of the environmental sustainability of technologies involving the use of such materials. This paper deals with the LCA of an innovative emulsion-based cold recycled mixture specifically conceived to be used as a sustainable solution for the surface finishing of unpaved rural roads. Two scenarios entailing the employment of recycled or virgin materials were analyzed with the assessment of global warming potential (GWP), energy requirement, and water consumption. Results obtained confirmed that the scenario entailing the use of recycled materials represents the most sustainable and environmentally friendly solution.
1. Introduction
The growing concerns regarding environmental issues and climate change have led the pavement construction industry to move towards increasingly sustainable solutions to preserve natural resources [1]. In this context, the recycling of by-products in paving mixtures represents a valuable option since it allows for the replacement of large volumes of virgin aggregates, thus contributing to reducing the depletion of raw materials [2,3,4]. The recycling of by-products appears to be especially suitable for rural roads, for which lower performance is generally required compared to high-volume highways and arterials [5].
Reclaimed asphalt pavement (RAP), obtained from the milling of existing asphalt pavements, and mineral sludge (MS), derived from industrial washing of natural aggregates in crushing plants, may be effectively used as alternative aggregates in the construction of pavement layers due to their large availability and problems faced in their stockpiling and/or disposal [6,7,8]. In fact, a previous research study conducted by the authors showed that RAP and MS can be successfully employed in large quantities in the production of emulsion-based cold recycled mixtures (CRM) for the surface finishing of unpaved rural roads [9].
In this paper, the environmental benefits related to the use of CRM were assessed using the life cycle assessment (LCA) methodology. To this purpose, the global warming potential (GWP), energy requirement, and water consumption related to the production, construction, and maintenance stages of the innovative mixture were analyzed and compared to a reference in which the use of only virgin materials is considered.
2. LCA: Scenarios and Results
Figure 1 shows the cross sections (4.50 m width and 30 cm thick) corresponding to the two different scenarios compared based on LCA.
Scenario A refers to the innovative proposed solution consisting of a 20 cm thick RA base layer covered by a 10 cm thick CRM finishing surface layer. Scenario B refers to the typical solution currently adopted in northern Italy for low-volume unpaved rural roads, consisting of a single 30 cm thick crushed virgin aggregates layer.
The LCA was performed using the PaLATE tool, properly customized in order to account for the reference geographic context analyzed in the present study. The system boundaries included materials production, construction, and maintenance operations, according to a cradle-to-gate approach. The in-service phase was kept out of the analysis, due to its negligible impact in comparative terms and uncertainty in the forecast of traffic spectra. The end-of-life phase was also excluded from the system boundaries since all materials have the potential to be fully reclaimed without requiring landfill disposal. The functional unit consists of 1 km of road with a service life of 10 years.
The life cycle inventory was based on both primary and secondary data. Primary data were collected through interviews with local companies, while secondary data were collected from the available literature [10,11,12,13]. The inventory of equipment and trucks employed in the production, construction, transportation, and maintenance activities (Table 1) was based on primary data, while emission factors were obtained from the literature.
The analyzed impact categories were global warming potential (GWP), energy requirement, and water consumption.
The results of the analysis obtained for the two scenarios are given in Table 2. It can be highlighted that the adoption of the technical solution proposed for scenario A led to an overall reduction of the environmental burdens, which was particularly relevant when considering water consumption and GWP.
A comparison between these two solutions is also provided in a graphical form in Figure 2, where the relative impacts in terms of GWP, energy requirement, and water consumption values are expressed as a percentage of those found for reference scenario B. Moreover, for each normalized impact, the relative contributions of materials production (MP), transportation (T), and construction/maintenance (C&M) phases are also provided.
It is interesting to observe that pavement construction and maintenance activities played a marginal role, as proven by contributions that were found to be always lower than 3%, regardless of the analyzed scenarios. The highest impacts were found to be those related to materials production. In particular, based on the comparison of the two solutions in terms of GWP and energy requirement, it was demonstrated that savings related to the use of a less amount of virgin aggregates were almost or totally offset by the innovative technical solution. This is due to the environmental burdens caused by the industrial production of the emulsion, the treatments of RAP, and the in-field preparation of CRM. On the other hand, relevant reductions in terms of water consumption were yielded by the dramatic decrease in the use of virgin aggregates. When focused on transportation, it can be noticed that the technical solution proposed in scenario A produced a reduction of more than 40% in the GWP and energy impact categories. Such a significant saving can be attributed to the use of in-place recycled materials that required fewer transportation distances with respect to solutions based on the use of virgin aggregates, as well as by the lower maintenance activities that are needed when bitumen-bound materials are used for wearing courses.
3. Concluding Remarks
In the present study, the environmental performances of two technical solutions for low-volume unpaved rural roads were evaluated and compared using LCA.
It was observed that the most critical stages are those related to materials production and transportation, while negligible impacts derive from construction and maintenance operations.
The outcomes of this LCA demonstrated the benefits, in terms of environmental impacts, associated with the considered innovative solution. Based on the assessment of GWP, energy requirement and water consumption related to materials production, transportation, construction, and maintenance operations, the proposed solution (which entails the use of large quantities of RAP and MS) outperformed the reference solution currently adopted for unpaved rural roads in northern Italy.
Further studies are certainly needed to extend the analysis to other impact categories and to widen the system boundaries.
Author Contributions
Conceptualization, L.T., P.P.R. and L.U.; methodology, L.T. and L.U.; formal analysis, L.T., P.P.R. and L.U.; investigation, L.T., P.P.R. and L.U.; resources, E.S. and O.B.; data curation, L.U.; writing—original draft preparation, L.T., P.P.R. and L.U.; writing—review and editing, L.T., P.P.R., O.B. and E.S.; supervision, E.S. and O.B. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data available under request.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Riviera, P.P.; Bellopede, R.; Marini, P.; Bassani, M. Performance-based re-use of tunnel muck as granular material for subgrade and sub-base formation in road construction. Tunn. Undergr. Space Technol. 2014, 40, 160–173. [Google Scholar] [CrossRef] [Green Version]
- Balaguera, A.; Carvajal, G.I.; Albertí, J.; Fullana-I-Palmer, P. Life cycle assessment of road construction alternative materials: A literature review. Resour. Conserv. Recycl. 2018, 132, 37–48. [Google Scholar] [CrossRef]
- Plati, C. Sustainability factors in pavement materials, design, and preservation strategies: A literature review. Constr. Build. Mater. 2019, 211, 539–555. [Google Scholar] [CrossRef]
- Salehi, S.; Arashpour, M.; Kodikara, J.; Guppy, R. Sustainable pavement construction: A systematic literature review of environmental and economic analysis of recycled materials. J. Clean. Prod. 2021, 313, 127936. [Google Scholar] [CrossRef]
- Gomes, G.J.C.; Magalhães, A.J.; Rocha, F.L.L.; Fonseca, A. A sustainability-oriented framework for the application of industrial byproducts to the base layers of low-volume roads. J. Clean. Prod. 2021, 295, 126440. [Google Scholar] [CrossRef]
- European Asphalt Pavement Association (EAPA). Asphalt in Figures 2019; European Asphalt Pavement Association: Brussels, Belgium, 2020. [Google Scholar]
- Choorackal, E.; Riviera, P.P.; Santagata, E. Mix design and mechanical characterization of self-compacting cement-bound mixtures for paving applications. Constr. Build. Mater. 2019, 229, 116894. [Google Scholar] [CrossRef]
- Hudson, W.; Little, D.; Razmi, A.; Anderson, A.; Weissmann, A. An Investigation of the Status of by-Product Fines in the USA, International Center for Aggregates Research; Research Report ICAR-101-1; International Center for Aggregates Research: Austin, TX, USA, 1997. [Google Scholar]
- Urbano, L.; Dalmazzo, D.; Riviera, P.P.; Baglieri, O.; Santagata, E. A Sustainable Cold-Recycled Solution for the Surface Finishing of Unpaved Rural Roads. Materials 2022, 15, 3920. [Google Scholar] [CrossRef]
- Blengini, G.A.; Garbarino, E. Resources and waste management in Turin (Italy): The role of recycled aggregates in the sustainable supply mix. J. Clean. Prod. 2010, 18, 1021–1030. [Google Scholar] [CrossRef]
- Eurobitume. Life Cycle Inventory: Bitumen; European Bitumen Association: Brussels, Belgium, 2012; ISBN 2-930160-26-8. [Google Scholar]
- European Environment Agency. EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019 Technical Guidance to Prepare National Emission Inventories; EEA Report No 13/2019; European Environment Agency: Copenhagen, Denmark, 2019; ISSN 1977-8449. [Google Scholar]
- Ecoinvent. Life Cycle Inventories of Production Systems; Swiss Centre for Life Cycle Inventories: Zürich, Switzerland, 2007. [Google Scholar]
Figure 1.
Cross-sections corresponding to the considered scenarios.
Figure 2.
Normalized impacts (ΔI) of GWP, energy, and water expressed as a percentage of the results of reference scenario B, with relative contributions of materials production (MP), transportation (T), and construction /maintenance (C&M) phases.
Figure 2.
Normalized impacts (ΔI) of GWP, energy, and water expressed as a percentage of the results of reference scenario B, with relative contributions of materials production (MP), transportation (T), and construction /maintenance (C&M) phases.
Table 1.
Equipment and trucks considered in the analysis.
| Equipment/Trucks | Activity |
|---|---|
| Crushing Plant | Crushing of virgin aggregates |
| Mobile Crushing Device | Crushing of RA |
| Wheel Loader + Blender | Production of CRM |
| Dump Trucks | Transportation of granular material |
| Tanker Trucks Paver and Roller | Transportation of fluid material Pavement construction |
Table 2.
GWP, energy requirement and water consumption for scenarios A and B.
| Impact | Scenario A | Scenario B |
|---|---|---|
| GWP (Mg of CO2eq) | 18.7 | 24.0 |
| Energy (MJ) | 253,169 | 263,651 |
| Water (m3) | 327 | 6701 |
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
MDPI and ACS Style
Urbano, L.; Tsantilis, L.; Riviera, P.P.; Baglieri, O.; Santagata, E. Life Cycle Assessment of a Sustainable and Innovative Solution for Unpaved Rural Roads. Eng. Proc. 2023, 36, 12. https://doi.org/10.3390/engproc2023036012
AMA Style
Urbano L, Tsantilis L, Riviera PP, Baglieri O, Santagata E. Life Cycle Assessment of a Sustainable and Innovative Solution for Unpaved Rural Roads. Engineering Proceedings. 2023; 36(1):12. https://doi.org/10.3390/engproc2023036012
Chicago/Turabian StyleUrbano, Leonardo, Lucia Tsantilis, Pier Paolo Riviera, Orazio Baglieri, and Ezio Santagata. 2023. "Life Cycle Assessment of a Sustainable and Innovative Solution for Unpaved Rural Roads" Engineering Proceedings 36, no. 1: 12. https://doi.org/10.3390/engproc2023036012
