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Life Cycle Assessment of Asphalt Roads: Decision Support at the Project Level
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.ORCID iD: 0000-0002-4270-8993
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 [en]
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: urn:nbn:se:kth:diva-156016ISBN: 978-91-87353-48-2 (print)OAI: oai:DiVA.org:kth-156016DiVA: diva2:763875
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
List of papers
1. Life Cycle Assessment Framework for Asphalt Pavements: Methods to Calculate and Allocate Energy of Binder and Additives
Open this publication in new window or tab >>Life Cycle Assessment Framework for Asphalt Pavements: Methods to Calculate and Allocate Energy of Binder and Additives
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.

Keyword
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:nbn:se:kth:diva-49783 (URN)10.1080/10298436.2012.718348 (DOI)000329962900002 ()2-s2.0-84893032210 (Scopus ID)
Note

QC 20150624

Available from: 2012-02-29 Created: 2011-11-29 Last updated: 2017-12-08Bibliographically approved
2. Life Cycle Assessment for the Green Procurement of Roads: A Way Forwar
Open this publication in new window or tab >>Life Cycle Assessment for the Green Procurement of Roads: A Way Forwar
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-156029 (URN)
Note

QS 2014

Available from: 2014-11-18 Created: 2014-11-18 Last updated: 2014-11-18Bibliographically approved
3. Life cycle cost analysis based on the fundamental cost contributors for asphalt pavements
Open this publication in new window or tab >>Life cycle cost analysis based on the fundamental cost contributors for asphalt pavements
2014 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 10, no 12, 1638-1647 p.Article in journal (Refereed) Published
Abstract [en]

A life cycle costing system should include the key variables that drive future costs in order to provide a framework for reducing the risk of under- or overestimating the future costs for maintenance and rehabilitation activities. In Sweden, price of oil products is mostly affected by the global economy rather than by the national economy. Whereas the price index of oil products has had a high fluctuation in different time periods, the cost fluctuation related to labour and equipment has been steady and followed the consumer price index (CPI). Contribution of the oil products was shown to be more than 50% of the total costs regarding construction and rehabilitation of asphalt pavements in Sweden. Consequently, it was observed that neither Swedish road construction price index (Vagindex) nor CPI has properly reflected the price trend regarding the asphalt pavement construction at the project level. Therefore, in this study, a framework is suggested in which energy- and time-related costs are treated with different inflation indices in order to perform a better financial risk assessment regarding future costs.

Keyword
user cost, rehabilitation, road and highways, maintenance, life cycle cost
National Category
Construction Management
Research subject
Civil and Architectural Engineering; Transport Science
Identifiers
urn:nbn:se:kth:diva-126485 (URN)10.1080/15732479.2013.837494 (DOI)000348941700002 ()2-s2.0-84908049055 (Scopus ID)
Note

QC 20150302

Available from: 2013-08-21 Created: 2013-08-21 Last updated: 2017-12-06Bibliographically approved
4. Considering the benefits of asphalt modification using a new technical LCA framework
Open this publication in new window or tab >>Considering the benefits of asphalt modification using a new technical LCA framework
2016 (English)In: Journal of Civil Engineering and Management, ISSN 1392-3730, E-ISSN 1822-3605, Vol. 22, no 5, 597-607 p.Article in journal (Refereed) Accepted
Abstract [en]

Asphalt mixtures properties can be enhanced by modifying it with additives. Even though the immediatebenefits of using polymers and waxes to modify the binder properties are rather well documented, the effects of suchmodification over the lifetime of a road are seldom considered. To investigate this, a newly developed open technical lifecycle assessment (LCA) framework was used to determine production energy and emission limits for the asphaltadditives. The LCA framework is coupled to a calibrated mechanics based computational framework that predicts the intimepavement performance. Limits for production energy of wax and polymers were determined for the hypotheticalcase studies to show how LCA tools can assist the additives manufacturers to modify their production procedures andhelp road authorities in setting ‘green’ limits to get a real benefit from the additives over the lifetime of a road. From thedetailed case-studies, it was concluded that better understanding of materials will lead to enhanced pavement design andcould help in the overall reduction of energy usage and emissions.

Place, publisher, year, edition, pages
Taylor & Francis, 2016
Keyword
life cycle assessment, asphalt binder additives, bitumen healing, calibrated mechanics based pavement design model, polymer, wax.
National Category
Environmental Sciences Infrastructure Engineering
Research subject
Civil and Architectural Engineering; Materials Science and Engineering; Transport Science
Identifiers
urn:nbn:se:kth:diva-102762 (URN)10.3846/13923730.2014.914084 (DOI)2-s2.0-84940706774 (Scopus ID)
Note

QC 20160418

Available from: 2012-09-25 Created: 2012-09-25 Last updated: 2017-12-07Bibliographically approved
5. Importance of systems approach for evaluating the life cycle environmental impacts of a road project
Open this publication in new window or tab >>Importance of systems approach for evaluating the life cycle environmental impacts of a road project
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Aggregates from two different sources and the effect of using a warm mix asphalt additive(WMAA) in asphalt mixtures were investigated in the laboratory. Different pavement designalternatives were generated using the laboratory data and analysed using a road life cycleassessment (LCA) framework. It was concluded that the effects of WMAAs must beevaluated on a case by case basis since WMAA interaction with the aggregate surfacemineralogy appears to play a significant role. Asphalt production and material transportationwere found to be the most energy consuming processes having high greenhouse gasemissions. The results presented also showed that having actual pavement material propertiesas the key attributes in LCA enables a pavement focused assessment of environmental costsassociated with different design options.

Keyword
Life cycle assessment; warm mix chemical asphalt additive; different aggregate sources; pavement design; asphalt pavements.
National Category
Civil Engineering Environmental Engineering
Research subject
Civil and Architectural Engineering; Transport Science
Identifiers
urn:nbn:se:kth:diva-156015 (URN)
Note

QS 2015

Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2015-02-18Bibliographically approved

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