Considering the benefits of asphalt modification using a new technical LCA framework (original) (raw)
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Journal of Civil Engineering and Management, 2015
Asphalt mixtures properties can be enhanced by modifying it with additives. Even though the immediate benefits of using 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. To investigate this, a newly developed open technical life cycle assessment (LCA) framework was used to determine production energy and emission limits for the asphalt additives. The LCA framework is coupled to a calibrated mechanics based computational framework that predicts the in-time pavement performance. Limits for production energy of wax and polymers were determined for the hypothetical case studies to show how LCA tools 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. From the detailed case-studies, it was concluded that better understanding of mate...
Life Cycle Assessment of Asphalt Pavements including the Feedstock Energy and Asphalt Additives
2012
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.
Transportation Research Part D: Transport and Environment, 2014
In order to assess sustainability of products and processes, different methodologies have been developed and used in the last years. In the road pavement construction area, most methodologies used for life cycle assessment (LCA) are essentially focused in the construction phase. The present paper analyses the importance of the use phase of a road in the LCA of different paving alternatives, namely by evaluating energy consumption and gaseous emissions throughout the road pavement's life. Therefore, a new LCA methodology for road pavements was developed, and the results of its application to a case study involving the construction of alternative pavement structures are discussed. The study intends to assess the influence of using more sustainable paving construction alternatives (asphalt recycling vs. conventional asphalt mixtures), and/or different surface course materials (which have a higher influence on the rolling resistance and, therefore, affect the performance during the use phase). The LCA results obtained for this case study showed that the reductions in energy consumption and gaseous emissions obtained during the use phase, for pavement alternatives with a lower rolling resistance surface course, are higher than the total amount of energy consumption and gas emissions produced during construction. It is therefore clear that some improvements in the characteristics of the surface course may have an effect over the road use phase that will rapidly balance the initial costs and gas emissions of those interventions. The LCA results obtained also showed that the sustainability of pavement construction may also be improved using recycled asphalt mixtures.
Life Cycle Energy and Cost Assessment Method for Modified Asphalt Pavements
2012
The importance of materials' selection for effective change in energy requirements of construction and service life cycle of asphalt pavement highways is well known. However, such energy related issues are rarely considered in the design and material selection process today. This is largely due to insufficient data and unclear methodology for translating effects in terms of environmental and economic savings. To address this deficiency a program was designed into which project specific information is inputted and used for comparison of alternative material and modification options in term of performance, cost, effective life span, and the magnitude of change in energy requirements. This paper includes a summary of this program that could be used as a design and materials' selection aid for asphalt pavements.
Hybrid life cycle assessment for asphalt mixtures with high RAP content
With the pavement industry adopting sustainable practices to align itself with the global notion of habitable environments, there has been growing use of life-cycle assessment (LCA). A hybrid LCA was used to analyze the environmental footprint of using a reclaimed asphalt pavement (RAP) content in asphalt binder mixtures. The analysis took into consideration the material, construction, and maintenance and rehabilitation phases of the pavement life cycle. The results showed significant reductions in energy consumption and greenhouse gas (GHG) emissions with an increase in RAP content. The contribution of the construction phase to the GHGs and energy consumption throughout pavement life cycle is minimal. Feedstock energy, though not consequential when comparing asphalt mixtures only, has a significant impact on total energy. Based on LCA analysis performed for various performance scenarios, breakeven performance levels were identified for mixtures with RAP. The study highlighted the importance of achieving equivalent field performance for mixtures with RAP and virgin mixtures.
Using Life Cycle Assessment to Optimize Pavement Crack-Mitigation
7th RILEM International Conference on Cracking in Pavements, 2012
Cracking is very common in areas having large variations in the daily temperatures and can cause large discomfort to the users. To improve the binder properties against cracking and rutting, researchers have studied for many years the behaviour of different binder additives such as polymers. It is quite complex, however, to decide on the benefits of a more expensive solution without looking at the long term performance. Life cycle assessment (LCA) studies can help to develop this long term perspective, linking performance to minimizing the overall energy consumption, use of resources and emissions. To demonstrate this, LCA of an unmodified and polymer modified asphalt pavement using a newly developed open LCA framework has been performed. It is shown how polymer modification for improved performance affects the energy consumption and emissions during the life cycle of a road. Furthermore, it is concluded that better understanding of the binder would lead to better optimized pavement design, hence reducing the energy consumption and emissions. A limit in terms of energy and emissions for the production of the polymer was also found which could help the polymer producers to improve their manufacturing processes, making them efficient enough to be beneficial from a pavement life cycle point of view.
Sustainability, 2020
Recycled and low-temperature materials are promising solutions to reduce the environmental burden deriving from hot mix asphalts. Despite this, there is lack of studies focusing on the assessment of the life-cycle impacts of these promising technologies. Consequently, this study deals with the life cycle assessment (LCA) of different classes of pavement technologies, based on the use of bituminous mixes (hot mix asphalt and warm mix asphalt) with recycled materials (reclaimed asphalt pavements, crumb rubber, and waste plastics), in the pursuit of assessing energy and environmental impacts. Analysis is developed based on the ISO 14040 series. Different scenarios of pavement production, construction, and maintenance are assessed and compared to a reference case involving the use of common paving materials. For all the considered scenarios, the influence of each life-cycle phase on the overall impacts is assessed to the purpose of identifying the phases and processes which produce the greatest impacts. Results show that material production involves the highest contribution (about 60-70%) in all the examined impact categories. Further, the combined use of warm mix asphalts and recycled materials in bituminous mixtures entails lower energy consumption and environmental impacts due to a reduction of virgin bitumen and aggregate consumption, which involves a decrease in the consumption of primary energy and raw materials, and reduced impacts for disposal. LCA results demonstrate that this methodology is able to help set up strategies for eco-design in the pavement sector.
Sustainability Assessment of Green Asphalt Mixtures: A Review
Environments, 2019
During recent decade, the pavement sustainability has received much attention by road agencies, companies, governments and research institutes. The aim of this paper is to introduce and evaluate the sustainability of the technologies developed or underdeveloped to address environmental issues of asphalt mixtures, and the waste materials and by-products that can be recycled and reused in asphalt production. Warm Mix Asphalt (WMA) technology, the most popular waste materials to substitute neat binder (crumb rubber modifier (CRM), recycled plastic (RP), vacuum tower bottoms (VTB)) and/or virgin aggregates (reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAs), construction and demolition (C and D) wastes, steel and copper slags), and bio-binders were evaluated with respect to their environmental and economic benefits and engineering performance as the main components of pavement sustainability. The performance evaluation was carried out by examining rutting, moisture susceptibility, thermal and fatigue cracking resistance. Two main environmental impacts, greenhouse gas (GHG) emission, and energy consumption were considered to study the environmental effects of these technologies and materials. Additionally, the economic effect was investigated considering initial cost and long-term benefit. Results of investigation illustrated that although each individual technology and waste material is valuable in terms of performance and/or the environment, specific combinations such as WMA + RAP, WMA + CRM, RAP + CRM, and WMA + CRM + RAP lead to further benefits. Notably, these combinations suffer from a lack of comprehensive economic analysis, thus, their sustainability cannot be fully assessed and is prone to future studies.
Sustainability
The carbon footprints of asphalt mixtures with increasing reclaimed asphalt pavement (RAP) content were estimated using a life-cycle assessment methodology. Three asphalt mixtures with different applications and technical requirements, namely porous asphalt (PA), stone mastic asphalt (SMA), and asphalt concrete (AC), were included. The technology leaps needed to achieve asphalt mixtures containing up to 93% RAP were modelled. Mixtures containing up to 57% RAP were hot-mix asphalts (175 °C), while mixtures containing more RAP were produced at 135 °C and 105 °C. The energy requirements and their respective carbon footprints were calculated based on the heat capacity of the aggregates, RAP, and other bituminous materials. Furthermore, the effects of changing the country’s electricity mix were also evaluated. A potential carbon footprint reduction of between 55% and 64% was found for one tonne of asphalt containing 93% RAP and produced at 105 °C compared to the 0% RAP mixture produced a...
Sustainability
Life cycle assessment (LCA) tools have been used by governments and city administrators to support the decision-making process toward creating a more sustainable society. Since LCA is strongly influenced by local conditions and may vary according to various factors, several institutions have launched cooperation projects to achieve sustainable development goals. In this study, we assessed the potential environmental enhancements within the production of road materials applied to the road network of Münster, Germany. We also compared traditional pavement structures used in Münster and alternative options containing asphalt mixtures with larger amounts of reclaimed asphalt pavement (RAP). Although the case study was conducted in Münster, the data collected and the results obtained in this study can be used for comparison purposes in other investigations. In the analysis, we considered all environmental impacts from raw material extraction to the finished product at the asphalt plant. ...