1,720,990 research outputs found
A comparative environmental life cycle assessment of road asphalt pavement solutions made up of artificial aggregates
Full text link: The construction and maintenance of road pavements entail detrimental impacts on the consumption of resources and damage to the natural environment but also make up an opportunity for the large-scale application of circular economy principles and innovative waste valorisation paths. The present study focuses on developing a comprehensive procedure to evaluate the technical and environmental sustainability of replacing high percentage of limestone aggregates with artificial aggregates from municipal solid waste incineration (MSWI) into hot or cold recycled asphalt mixtures for asphalt pavements. The technical feasibility of the designed mixtures was investigated in terms of the main physical and mechanical properties of both the raw materials and the asphalt mixtures with content of artificial aggregates or sand in the range 25-40 % by mass. The environmental feasibility of the asphalt mixtures was evaluated through the SEM-EDS technique, the analysis of the eluate of the leaching test and the ecotoxicity for living organisms. Afterwards, the life cycle assessment (LCA) was applied to detect the critical spots of the life cycle of 1 m2 of a 6 cm-thick binder layer with high percentage of artificial aggregates or sand built and maintained through 30 years analysis period according to 18 impact category indicators. The main results show that, recycling the artificial aggregates into hot asphalt mixtures has on average a negligible effect on the overall environmental performance of the life cycle, and appears to be detrimental only for the consumption of fossil resources due to the higher optimum bitumen content. Looking at the results for cold mixes, the introduction of the artificial aggregates has an effect on the predicted durability of the asphalt layers, which is maximized in the case of coarse artificial aggregates. Consequent environmental benefits regard the global warming potential, fossil resource scarcity and freshwater eutrophication indicators
Rheological and mechanical properties of HMA containing fly ashes as alternative filler
No full textThis study defined the mechanical/volumetric properties and the environmental compatibility of bituminous mixtures containing fly ashes as alternative of traditional limestone filler. The research study is articulated in different steps as follows: (a) characterization of fly ashes according to EN 13043 Standard; (b) environmental compatibility analysis of mastics containing fly ashes by a leaching test; (c) stiffness evaluation of the mastics containing limestone and fly ash filler by static testing, as Delta Ring and Ball Test, and dynamic testing, as Frequency Sweep Test; (d) mechanical and volumetric characterization of asphalt concrete containing fly ashes and limestone filler starting from a phase of mix design of hot mix asphalt mixtures. The characteristics of stiffness of the bituminous mixtures has been evaluated on the optimum HMA through a dynamic test with a sinusoidal load. Then, the ability of two different HMA to endure a permanent deformation was evaluated by a Repeated Load Axial Test. The results has shown that mixtures of Hot Mix Asphalt with flying ashes as filler, compared to Hot Mix Asphalt containing limestone filler, is preferred in terms of mechanical performances and relevant environmental compatibility evaluated with the leaching test
Analytical Assessment of Effective Maintenance Operations on At-Grade Unsignalized Intersections
No full textThis chapter describes a methodological structure to support and improve the decision-making process for redesigning the geometric configurations of substandard sites and thus reduce crash risk factors on at-grade three-leg and four-leg intersections with stop-control on minor roads and single-lane roundabouts belonging to a two-lane rural road network located in Southern Italy. Starting from an initial evaluation of the risk level at each investigated site and adopting a procedure developed by the Italian National Research Council based on an estimated crash rate level, a more precise hierarchy of intersections with “black” rankings was developed. In addition, new geometric configurations for the most hazardous sites were suggested based on a statistical comparison in terms of safety and Level of Service (LoS). The effectiveness of the strategies was validated by computing the expected LoS and safety by adopting an empirical Bayesian analysis and performance functions centered on a revised Highway Safety Manual procedure reflecting the context of the study
INDIRECT TENSILE STRENGTH METHOD FOR DEFINING A PROPER PRACTICE OF ASPHALT MIXTURES DESIGN
No full textThis paper shows the results of a laboratory investigation of indirect tensile strength test effects on bituminous mixtures characterization. In particular, the research focusses, in the first analysis, on the procedure of Marshall mix design, where 4 different mixtures of hot mix asphalt (HMA) were prepared at different bitumen contents between 3.5% and 4.25% by total aggregate weight at 0.25% increments. In the second phase, bituminous specimens made-up by gyratory compactor in compliance with Marshall optimization were tested to evaluate their indirect tensile strength. It was ascertained how the air voids percentage and indirect tensile strength can change by varying the number of revolutions during gyratory compaction and the height of specimens. A one-way ANOVA test was finally carried out to verify whether statistically significant differences exist in terms of mechanical properties when the number of revolutions and the specimen size change. This research may help to provide administrations with fast laboratory procedures to use in situ for all activities related to acceptance of mixtures
Leveraging Infrastructure BIM for Life-Cycle-Based Sustainable Road Pavement Management
Full text linkThe latest developments in the field of road asphalt materials and pavement construction/maintenance technologies, as well as the spread of life-cycle-based sustainability assessment techniques, have posed issues in the continuous and efficient management of data and relative decision-making process for the selection of appropriate road pavement design and maintenance solutions; Infrastructure Building Information Modeling (IBIM) tools may help in facing such challenges due to their data management and analysis capabilities. The present work aims to develop a road pavement life cycle sustainability assessment framework and integrate such a framework into the IBIM of a road pavement project through visual scripting to automatically provide the informatization of an appropriate pavement information model and evaluate sustainability criteria already in the design stage through life cycle assessment and life cycle cost analysis methods. The application of the proposed BIM-based tool to a real case study allowed us (a) to draw considerations about the long-term environmental and economic sustainability of alternative road construction materials and (b) to draft a maintenance plan for a specific road section that represents the best compromise solution among the analyzed ones. The IBIM tool represents a practical and dynamic way to integrate environmental considerations into road pavement design, encouraging the use of digital tools in the road industry and ultimately supporting a pavement maintenance decision-making process oriented toward a circular economy
Investigating the environmental impacts and engineering performance of road asphalt pavement mixtures made up of jet grouting waste and reclaimed asphalt pavement
No full textAs a response to the reduction of environmental pollution and energy consumption in the maintenance or building of a road pavement, this research aims to provide innovative asphalt mixture solutions when designing asphalt base layers containing solidified Jet Grouting Waste (JGW) particles. This involved adding (or not) solutions made up from Reclaimed Asphalt Pavement (RAP) obtained by milling old pavements. The first step focused on a JGW and RAP leaching test before going on to design two non-traditional mixtures: a) a hot asphalt mixture made by replacing 4% of the limestone filler by the total weight of the aggregates with JGW (HMAJ), mixing all of them at a high temperature (160 ÷ 180°C), and b) a cold asphalt mixture made by adding 3% JGW as a filler, 70% RAP (CMRAJ), and 27% limestone by the total weight of the aggregates at low temperatures (40 ÷ 50°C). These innovative mixtures were investigated from the point of view of engineering performance by ascertaining their physico-mechanical features and environmental impact through a Life Cycle Assessment (LCA) test. Further comparison with traditional ones was then carried out using a hot mix asphalt (HMA) and a cold mixture made up from RAP, substituting a portion of the limestone aggregates (CMRA). Such mixtures are subject to special tender specification requirements. Engineering performance assessment showed that, compared with HMA, when JGW is added to both hot and cold mixtures, the ITS is 11% higher for HMAJ and CMRAJ, and cumulative strain is reduced by 17% for HMAJ and 39% for CMRA, while the cold asphalt mixtures (CMRA and CMRAJ) showed greater stiffness levels (on average 50%) at all test temperatures (10, 25, and 40°C). LCA analysis provided significant results for the solutions being compared. Specifically, use of HMAJ as the base layer helped save 65 g/m3 of CO2 compared with HMA, at the same time helping to reduce 29.7 kg of CO2eq./m3 global warming potential. On the other hand, the use of CMRA as the base layer, again compared with the HMA, helped save 45 g/m3 of phosphorous compound emissions in water. In terms of terrestrial ecotoxicity and human non-carcinogenic toxicity, the best performance was obtained using a CMRAJ mixture, whose indicators showed a 60% reduction compared with the HMA solution base layer
BIM-LCA Integration Framework for Sustainable Road Pavement Maintenance Practices
Full text linkThe latest advancements in road asphalt materials and construction technologies have increased the difficulty for engineers to select the appropriate pavement design solution with consideration of life cycle assessment (LCA) methodology. On the other hand, infrastructure building information modeling (BIM) tools allow practitioners to efficiently store and manage large amounts of data, supporting decision making in road asphalt pavement design and management. This research contributes to setting up a dynamic LCA tool for the specific evaluation of designed road asphalt pavement solutions involving alternative materials and advanced recycling technologies; the tool is structured to minimize the need of input data by the designer, that are usually unknown during the early design stage, and automate the entire LCA calculation process to reduce the designer efforts and avoid any errors during data transcription. A traditional BIM workflow was integrated with additional user-defined property sets to simultaneously compute the environmental impact of the entire life cycle of the asphalt pavement, and dynamically update the result basing on the design thickness of the pavement layers, the specific features of materials and an external database of several life cycle impact category indicators that can be edited and updated gradually during more advanced design stage. The proposed BIM-LCA aims to be a practical and dynamic way to integrate environmental considerations into road pavement design, encouraging the use of digital tools in road industry and ultimately supporting a pavement maintenance decision-making process oriented toward circular economy
Exploring the effect on the environment of encapsulated micro- and nano-plastics into asphalt mastics for road pavement
No full text: A new environmental problem is represented by the huge transformation of plastic waste released into the environment into small fragments, the so called micro- and nano-plastics, due to atmospheric phenomena. The smaller the size of the plastic fragments, the more their spreading into environmental compartments. The aim of this study is to test encapsulation into asphalt mastics of waste plastic material (WPM) as sustainable strategy to obtain road flexible pavements and to evaluate the potential release in water of micro and nano plastics. A new mastic mixing method was developed to blend the WPM with the bitumen contained into a bitumen emulsion (BE60/40) by adopting low mixing temperatures. Three different WPM contents, equal to 5, 10 and 20% by the weight of the bitumen contained in the BE60/40, were adopted to produce the mastics; the mastics' rheological properties, obtained by frequency sweep and multiple stress creep and recovery tests, were compared to those of a traditional asphalt mastic containing limestone filler. The aging of asphalt mastics was analyzed by soaking them in water and gradually lowering and raising temperature between -10 and 60 °C at predefined intervals. The addition of WPM improved greatly the asphalt mastic performance; in particular, for a WPM content of 10%, the rheological response in terms of stiffness remained unchanged after the mastic underwent thermal excursions in water. Encapsulation of micro and nano plastics into mastics reduced of more than 99% their potential water release
Integration of life cycle assessment into a decision support system for selecting sustainable road asphalt pavement mixtures prepared with waste
No full textPurpose. A challenge that the road paving sector is facing concerns the achievement of highly performing bituminous asphalt mixture solutions that do not negatively impact the environment. New environmentally sound asphalt production and recycling technologies are becoming more and more widespread, but their practical application is still hindered by the lack of appropriate decision-making strategies by the administrations. In this study, innovative asphalt mixtures were compared through a novel multi-criterion and sensitivity analysis framework for selecting the best solutions.
Methods. A new decision support system has been implemented to choose the best paving alternative between nine asphalt mixtures containing different marginal materials for the binder and base layer of a flexible pavement. The methodological steps taken to reach the definition of the optimal solution concerned (1) mechanical analysis of the designed asphalt mixtures by laboratory investigation, (2) calculation of life cycle assessment indicators using the ReCiPe method, (3) application of the ELECTRE method for the identification of the optimal solution on the basis of both mechanical and environmental performance considering a traditional weight vector, and (4) sensitivity analysis based on 27 different configurations of weight vectors.
Results and discussion. The results of this work revealed that the hot asphalt solutions for the binder layer utilizing jet grouting waste and fly ash in substitution of natural fillers reached the best engineering and environmental performance, respectively. Between the asphalt mixtures for the base layer, the cold recycled asphalt containing reclaimed asphalt pavement and jet grouting waste reached, at the same time, the best environmental performance, the minimum value of permanent deformation, and the highest stiffness at 40 °C. The ELECTRE method and sensitivity analysis demonstrated that the purpose of jet grouting for making both hot and cold solutions is the best-compromise solution of environmental and mechanical performance.
Conclusions. The proposed framework allows the quantitative assessment of sustainable road asphalt pavement solutions and fits the needs of several engineering fields where a trade-of between the mechanical and environmental performance of multiple construction materials must be established. Future development of this framework could include cost indicators to address the sustainability of the solutions in detail
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