Impact Analysis Using Life Cycle Assessment of Asphalt Production from Primary Data

Identifying the opportunities for sustainable bitumen production in India

The present study assessed the environmental impacts due to bitumen production in India using life cycle assessment approach. The impacts were calculated for production of 1 t of bitumen and system boundary covered extraction of resources, processing at refinery, transportation of bitumen and storage at the production site. In this study, five scenarios were considered to estimate the impacts reduction assuming different future electricity mix and thermal energy source. Crude oil extraction phase had contributed highest (91%) followed by refinery phase (4%), then transportation (3%) and at last storage of bitumen (2%). The normalization results found that the bitumen production had highest impacts on abiotic depletion fossil and lowest impact on eutrophication. Scenario S4 had the least environmental impacts and provided the overall reductions of 33% compared to the baseline scenario. Scenario S4 reduced the impacts significantly on acidification (51%), eutrophication (30%), and human toxicity (71%), but the reductions were not significant on global warming (11%) and increased the impacts on abiotic depletion fossil (1%). The results of sensitivity analysis found that thermal energy obtained from hard coal consumed during bitumen production is the most sensitive parameter for all the impact categories. The uncertainty analysis showed that the results of this study are reliable and had standard deviation less than 5% for all the impact categories. The findings of the present study will help the decision makers and concerned authorities to reduce the environmental impacts from bitumen production in India.

The efficiency of bio-char as bitumen modifier

Improving the mechanical properties of bitumen is an important goal for road pavements design. For this reason, new compounds are now being sought for testing as bitumen modifiers. In this work, the authors studied the effect that two different chars have on two 50/70 bitumens with different chemical and physical characteristics. A complete morphological, surface and bulk characterization of the two additives was carried out. In addition, rheology, Nuclear Magnetic Resonance (NMR) relaxometry and atomic force microscopy were used to analyze the effect that the two additives exert on the properties of the bitumens. According to the results, the char sample with high porosity could be used as a modifier of mechanical properties, while no rejuvenation effects were observed for either of the two additives tested. In addition, the two additives do not give rise to segregation phenomena.

Comparative Life Cycle Assessment (LCA) of Porous Asphalt Mixtures with Sustainable and Recycled Materials: A Cradle-to-Gate Approach

The road and construction sectors consume a large number of natural resources and energy, contributing significantly to waste generation and greenhouse gas emissions (GHG). The use of recycled aggregate from construction and demolition waste as a substitute for virgin aggregate is a current practice in the construction of new road sections. Additionally, in recent years, there has been an increasing focus on finding alternatives to bitumen for binders used in asphalt mixes. This study investigates and compares the impacts associated with two porous asphalt mixtures produced with CDW aggregates, virgin aggregates, and a polyolefin-based synthetic transparent binder through an LCA methodology. A cradle-to-gate approach was employed. Model characterization for calculating the potential environmental impacts of each porous asphalt mixture was performed using the ReCipe 2016 assessment method at the midpoint and endpoint levels. The results are presented with reference to a baseline scenario corresponding to a porous asphalt mixture, confirming the benefits associated with the use of recycled aggregates and in some cases the benefits of not using bitumen-based binders. This work contributes to the understanding of the importance of choosing the least environmentally damaging solution during the production or rehabilitation of road pavement infrastructure.

A Comparative Review of Hot and Warm Mix Asphalt Technologies from Environmental and Economic Perspectives: Towards a Sustainable Asphalt Pavement

The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150-180 °C), the latest research on pavement energy consumption and carbon dioxide (CO₂) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also provides a healthy work environment and reduces exposure to fumes. Replacing HMA with WMA can reduce production costs because of the 20-75% lower energy consumption in WMA production. It was also released that the reduction in energy consumption is dependent on the fuel type, energy source, material heat capacity, moisture content, and production temperature. Other benefits of using WMA are enhanced asphalt mixture workability and compaction because the additives in WMA reduce asphalt binder viscosity. It also allows for the incorporation of more waste materials, such as reclaimed asphalt pavement (RAP). However, future studies are recommended on the possibility of using renewable, environmentally friendly, and cost-effective materials such as biomaterials as an alternative to conventional WMA-additives for more sustainable and green asphalt pavements.

A 3D-FE Model for the Rutting Prediction in Geogrid Reinforced Flexible Pavements

Permanent deformation (rutting) is an important disturbing failure on flexible road pavements. This phenomenon appears on the flexible pavement as longitudinal depressions, and it is a consequence of the degradation of materials under high traffic loading based on consolidation/densification, surface wear, plastic/shear flow, and mechanical deformation. Hence, the rutting phenomenon depends on the accumulation of permanent deformations on pavement surfaces subjected to repeated wheel loads. In recent years, several studies have confirmed that the service life of asphalt pavements can be increased by using geosynthetics between or within layers because of the improved mechanical properties. The aim of this paper is to present the results of the 3D-finite element (FE) simulations and the development of the rutting phenomenon in a traditional flexible pavement and a reinforced one, both subjected to a cyclic load. Through Abaqus/CAE software, a road section reinforced by a geogrid was analyzed and compared with a traditional road section to investigate the advantages given by the geosynthetic completely embedded at two-thirds of the asphalt concrete layer (AC) in terms of permanent deformations. The results show the capability of the proposed FE study, that uses the plasticity model of Drucker-Prager for unbound materials combined with the simple creep law to model HMA layers to predict the permanent deformation distribution.

Environmental Impact Assessment of Different Warm Mix Asphalts

Within the last decade, much attention has been focused on determining viable techniques for producing sustainable asphalt mixtures and minimizing fuel use and greenhouse gas emissions. Thus, warm mix asphalt (WMA) has become a topic of significant interest among road specialists as it offers a potential solution for reducing the environmental impact of the asphalt mixtures due to the decreased temperatures they require for mixing and compaction compared to hot mix asphalt (HMA). The present study is focused on the Life Cycle Assessment (LCA), according to a “Cradle-to-Gate” approach, of hot mix asphalt and warm mix asphalt prepared with locally available materials and different warm mix additives such as organic additives, chemical additive, and synthetic zeolite. For the analysis of the environmental impact of the warm mix asphalts was used a dedicated software for modeling and evaluating the LCA. The WMA prepared with chemical additive or organic additive led to a decrease of the environmental impact, in the production phase, compared to HMA. The study reveals that the raw materials extraction has the greatest impact on the environment in all studied cases, followed by the actual production phase of the asphalt mixture. For WMA produced with additives there was a decrease in the global impact on the environment compared to HMA.

Comprehensive Life Cycle Environmental Assessment of Preventive Maintenance Techniques for Asphalt Pavement

Preventive maintenance (PM) is regarded as the most economical maintenance strategy for asphalt pavement, but the life cycle environmental impacts (LCEI) of different PM techniques have not yet been comprehensively assessed and compared, thus hindering sustainable PM planning. This study aims to comprehensively estimate and compared the LCEI of five PM techniques then propose measures to reduce environmental impacts in PM design by using life cycle assessment (LCA), including fog seal with sand, micro-surfacing, composite seal, ultra-thin asphalt overlay, and thin asphalt overlay. Afterwards, ten kinds of LCEI categories and energy consumption of PM techniques were compared from the LCA phases, and inventory inputs perspectives, respectively. Results show that fog seal with sand and micro-surfacing can lower all LCEI scores by more than 50%. The environmental performance of five PM techniques provided by sensitivity analysis indicated that service life may not create significant impact on LCA results to some extent. Moreover, four PM combination plans were developed and compared for environmental performance, and results show that the PM plan only includes seal coat techniques that can reduce the total LCEI by 7–29% in pavement life. Increasing the frequency of seal coat techniques can make the PM plans more sustainable.

A Novel Integrated Interval Rough MCDM Model for Ranking and Selection of Asphalt Production Plants

Asphalt production plants play an important role in the field of civil engineering, but also in the entire economic system since the construction of roads enables uninterrupted functioning within it. In this paper, the ranking of asphalt production plants on the territory of the Autonomous Province of Vojvodina has been performed. The modern economy needs contemporary models and methods to solve complicated MCDM problems and, for these purposes, it has been developed an original Interval Rough Number (IRN) Multi-criteria decision-making (MCDM) model that implies an extension of two methods belonging to the field with interval rough numbers. After forming a list of eight most significant criteria for assessing the efficiency of asphalt production plants, the Interval Rough Number PIvot Pairwise RElative Criteria Importance Assessment (IRN PIPRECIA) method was developed to determine the significance of the criteria. A total of 21 locations with asphalt mixture installation were considered. For that purpose, seven asphalt production plants were included, and for their ranking, the IRN EDAS (Evaluation based on Distance from Average Solution) method was created. The aim of this paper is to develop a novel interval rough model that can be useful for determining the efficiency of asphalt production plants. Averaging in group decision-making (GDM) for both methods was performed using an IRN Dombi weighted geometric averaging (IRNDWGA) aggregator. The obtained results show that (A15) Ruma (SP)–Mačvanska Mitrovica–Zasavica has the best characteristics out of the set of locations considered in this study. However, Alternatives A6 and A19 are also variants with remarkably good characteristics since there is very little difference in values compared to the first-ranked alternative. Also, the obtained results have shown that the developed model is applicable, which is proven through a comparative analysis.