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Life Cycle Assessment Framework for Asphalt Pavements: Methods to Calculate and Allocate Energy of Binder and Additives
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.ORCID iD: 0000-0002-4270-8993
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms). (FMS)
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.ORCID iD: 0000-0003-0889-6078
2014 (English)In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 15, no 4, 290-302 p.Article in journal (Refereed) Published
Abstract [en]

The construction, maintenance and disposal of asphalt pavements may lead to considerable environmental impacts, in terms of energy use and emissions during the life of the pavement. In order to enable quantification of the potential environmental impacts due to construction, maintenance and disposal of roads, an open life cycle assessment (LCA) framework for the asphalt pavements is presented in this paper. Emphasis was placed on the calculation and allocation of energy used for binder and additives at the project level. It was concluded from this study that when progressing from LCA to its corresponding life cycle cost, the feedstock energy of the binder becomes highly relevant as the cost of the binder will be reflected in its alternative value as fuel. Regarding additives like wax, a framework for energy allocation was suggested. The suggested project level LCA framework was demonstrated in a limited case study of a Swedish asphalt pavement. It was concluded that the asphalt production and transporting materials were the two most energy-consuming processes, emitting most greenhouse gases depending on the fuel type and electricity mix.

Place, publisher, year, edition, pages
2014. Vol. 15, no 4, 290-302 p.
Keyword [en]
Life Cycle Assessment, feedstock energy, asphalt binder additives, mass-energy flows
National Category
Infrastructure Engineering Other Environmental Engineering
Research subject
Civil and Architectural Engineering; Transport Science
Identifiers
URN: urn:nbn:se:kth:diva-49783DOI: 10.1080/10298436.2012.718348ISI: 000329962900002Scopus ID: 2-s2.0-84893032210OAI: oai:DiVA.org:kth-49783DiVA: diva2:460290
Note

QC 20150624

Available from: 2012-02-29 Created: 2011-11-29 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Life Cycle Assessment of Asphalt Pavements including the Feedstock Energy and Asphalt Additives
Open this publication in new window or tab >>Life Cycle Assessment of Asphalt Pavements including the Feedstock Energy and Asphalt Additives
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Roads are assets to the society and an integral component in the development of a nation’s infrastructure. To build and maintain roads; considerable amounts of materials are required which consume quite an amount of electrical and thermal energy for production, processing and laying. The resources (materials and the sources of energy) should be utilized efficiently to avoid wastes and higher costs in terms of the currency and the environment.

In order to enable quantification of the potential environmental impacts due to the construction, maintenance and disposal of roads, an open life cycle assessment (LCA) framework for asphalt pavements was developed. Emphasis was given on the calculation and allocation of energy used for the binder and the additives. Asphalt mixtures properties can be enhanced against rutting and cracking by modifying the binder with additives. Even though the immediate benefits of using additives such as polymers and waxes to modify the binder properties are rather well documented, the effects of such modification over the lifetime of a road are seldom considered. A method for calculating energy allocation in additives was suggested. The different choices regarding both the framework design and the case specific system boundaries were done in cooperation with the asphalt industry and the construction companies in order to increase the relevance and the quality of the assessment.

Case-studies were performed to demonstrate the use of the LCA framework. The suggested LCA framework was demonstrated in a limited case study (A) of a typical Swedish asphalt pavement. Sensitivity analyses were also done to show the effect and the importance of the transport distances and the use of efficiently produced electricity mix. It was concluded that the asphalt production and materials transportation were the two most energy consuming processes that also emit the most GreenHouse Gases (GHG’s). The GHG’s, however, are largely depending on the fuel type and the electricity mix. It was also concluded that when progressing from LCA to its corresponding life cycle cost (LCC) the feedstock energy of the binder becomes highly relevant as the cost of the binder will be reflected in its alternative value as fuel. LCA studies can help to develop the long term perspective, linking performance to minimizing the overall energy consumption, use of resources and emissions. To demonstrate this, the newly developed open LCA framework was used for an unmodified and polymer modified asphalt pavement (Case study B). It was shown how polymer modification for improved performance affects the energy consumption and emissions during the life cycle of a road. From the case study (C) it was concluded that using bitumen with self-healing capacity can lead to a significant reduction in the GHG emissions and the energy usage.  Furthermore, it was concluded that better understanding of the binder would lead to better optimized pavement design and thereby to reduced energy consumption and emissions. Production energy limits for the wax and polymer were determined which can assist the additives manufacturers to modify their production procedures and help road authorities in setting ‘green’ limits to get a real benefit from the additives over the lifetime of a road.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xi, 25 p.
Series
Trita-TSC-LIC, ISSN 1653-445X ; 12:008
Keyword
Life Cycle Assessment; feedstock energy; asphalt binder additives; mass-energy flows; bitumen healing; wax; polymer
National Category
Infrastructure Engineering Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-102763 (URN)978-91-85539-96-3 (ISBN)
Presentation
2012-10-29, B25, Brinellvägen 23, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20120926

Available from: 2012-09-26 Created: 2012-09-25 Last updated: 2012-09-26Bibliographically approved
2. Life Cycle Assessment of Asphalt Roads: Decision Support at the Project Level
Open this publication in new window or tab >>Life Cycle Assessment of Asphalt Roads: Decision Support at the Project Level
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transport infrastructures such as roads are assets for the society as they not only ensure mobility but also strengthen society’s economy. Considerable amount of energy and materials, that include bitumen, aggregates and asphalt, are required to build and maintain roads. Improper utilization of energy and/or use of materials may lead to more waste and higher costs. The impact on the environment cannot be neglected either. Life cycle assessment (LCA) as a method can be used to assess the environmental impacts of a road system over its entire life time. Studying the life cycle perspective of roads can help us improve the technology in order to achieve a system that has a lower impact on the environment. There are number of LCA tools available. However, implementation of such tools is still unseen in real road projects. This clearly indicates that there are gaps which are needed to be filled in order to bring these tools into practice. An open road LCA framework was developed for the asphalt roads in order to help in decision support at the late project planning stage such as that related to the green procurement. The framework takes into account the construction, maintenance and end of life phases and focuses on energy and greenhouse gas (GHG) emissions. Threshold values for the production of some additives were also determined to show how LCA tools can help material suppliers to improve the road materials production processes and the road authorities to set limits on the use of different materials based on the environmental criteria. Additive consideration and feedstock energy in road LCAs were also identified as gaps that were looked in detail. The attributes that are important to consider in an asphalt road LCA that seeks to serve as a decision support in a procurement situation are described.

A brief literature review was carried out that focused on project LCAs, and specifically those considering pavements, as this level is assumed to be appropriate for questions relevant in a procurement situation. Following the different standards; road LCAs developed all over the world have generated a lot of knowledge and the studies have been different from each other such as in terms of goals and system boundaries. Hence, the patterns observed have been very different from study to study. It was also difficult to assess the decision support level for which the various LCA frameworks or tools were developed. It is important to define system boundaries based on where in the system the decision support is needed. For LCA to be useful for decision support in a procurement situation, it is important to have a clear understanding of the attributes that constitute the life cycle phases and how data of high quality for them are obtained. The level of consistency and transparency of road LCAs becomes increasingly important in pre-procurement and procurement situations. The key attributes used in a road LCA should mirror the material properties used in a pavement design and therefore be closely linked to the performance of the road in its life cycle.

From the different case studies, it was found that asphalt production and transportation of materials are usually highest in the energy and GHG emissions chain. It is highly favorable to have the quarry site, the asphalt plant and the construction site not far from each other and to use the electricity that has been produced in an efficient way. Based on the laboratory test results, it is shown that the effects of chemical warm mix asphalt additives (WMAA)s must be evaluated on a case by case basis since WMAA interaction with the aggregate surface mineralogy appears to play a significant role and thus affects its long term structural behavior. Using the material properties obtained from the Superpave indirect tensile test (IDT) results, pavement thickness design was done in which Arlanda aggregate based asphalt mixtures resulted in thinner pavements as compared to Skärlunda aggregate based asphalt mixtures for the same design life period. Energy (feedstock and expended) saving and reduction in GHG emissions were also seen with addition of WMAA, for both aggregate type cases, based on the data used. Importantly, the results presented illustrate the importance of a systems based LCA approach for evaluating the sustainability for different design and construction options. In this context, having actual pavement material properties as the key attributes in the LCA enables a pavement focused assessment of environmental costs associated with different design options.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vi, 61 p.
Series
TRITA-TSC-PHD, 14:006
Keyword
Asphalt roads; life cycle assessment; feedstock energy; warm mix asphalt additives; green procurement; decision support; laboratory investigation; pavement design.
National Category
Civil Engineering Environmental Engineering
Research subject
Civil and Architectural Engineering; Transport Science
Identifiers
urn:nbn:se:kth:diva-156016 (URN)978-91-87353-48-2 (ISBN)
Public defence
2014-12-11, Kollegiesalen (the old chapel), Brinellvägen 8, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20141118

Available from: 2014-11-18 Created: 2014-11-17 Last updated: 2014-11-18Bibliographically approved

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