Ali Azhar Butt

Life cycle assessment framework for asphalt pavements: methods to calculate and allocate energy of binder and additives

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.

Life cycle cost analysis based on the fundamental cost contributors for asphalt pavements

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 (Vägindex) 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.

Considering the benefits of asphalt modification using a new technical life cycle assessment framework

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, ...

Using life cycle assessment to optimize pavement crack-mitigation

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.

Assessment of the attributes based life cycle assessment framework for road projects

Abstract A number of life cycle assessment (LCA) tools have been suggested for pavements. However, very few have been adopted by the road authorities. The key reasons for this lack of implementation have been the tendency for very broad LCA analyses that include system boundaries considerably beyond the more natural system boundaries associated with road design, construction and maintenance as well as the lack of available LCA tools that have attributes that reflect key road properties. In this paper, a new attribute based pavement LCA framework is evaluated for use on real road materials. 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 design alternatives were generated using the laboratory data and analysed using the road LCA framework. Asphalt production and material transportation were found to be the most energy-consuming processes. The results presented show that having actual pavement material properties as the key attributes in LCA enables a pavement-focused assessment of environmental impacts associated with different design options, and LCA can help in decision support by evaluating environmental impacts of different design alternatives in a project planning/design stage.