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.

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Bituminous sub-ballast in railway track-bed can mitigate the variation of the moisture content in the subgrade and reduce vertical stiffness variations of the track leading to a more durable infrastructure. Nevertheless, durability is only one of the aspects that affects the sustainability of an infrastructure. Other relevant aspects are related to the environmental and economic issues. This research work joins the worldwide effort towards a paradigm shift in civil engineering devoted to assess the sustainability of infrastructures at the design stage. With this in mind, in this study different alternative bituminous sub-ballast mixtures containing recycled materials, namely crumb rubber (CR) and reclaimed asphalt pavements (RAP) were compared by means of the results of a Life-Cycle Assessment (LCA). In comparison with a traditional bituminous sub-ballast the Crumb Rubber Modified (CRM) mixtures showed higher impacts due to the treatment of the rubber as well as the higher amount of bitumen employed in the mixture. In turn, when RAP is used, the LCA results report an improvement of all the indicators considered. The reduction of the impacts is even higher when full blending between the aged and the virgin binder is assumed because it allows reducing the amount of virgin bitumen employed. The results are intended to be used by engineering experts and practitioners to make more assertive judgments on the advantages and disadvantages associated with the use of emerging and commonly called sustainable strategies and practices for railway track-bed.

This paper proposes a new visco-elastoplastic constitutive model for asphalt concretes able to reproduce the non linear time-dependent behaviour of such materials.The constitutive model has been developed with the aim of making it fit specific experimental features previously observed. Moreover the proposed formulation will be demonstrated to be fully consistent with general thermodynamic requirements. Apart from a rigorous analytical formulation; a corresponding rheological sketch of the model is also given. From this representation, it can be shown that the model is essentially a combination of a generalized Maxwell model and a hardening visco-plastic element.

Minimizing the environmental impacts is a challenging task to achieve sustainability in road constructions. Although they are only temporary, the environmental burdens of building activities can have a great impact on the environment and communities, and must be properly assessed and mitigated. A comprehensive evaluation of the impacts requires the consideration of all construction activities, construction sites and the type and operation time of off-road machines and plants that will be used in each site. In this paper, a case study relating to the project of a motorway was carried out with the following objectives: (i) to estimate the dust and gases arising from the whole construction process and identify the most critical pollutants in terms of emitted quantity; (ii) to investigate the worksites, activities and processes with the greatest impact from an emissive standpoint, and (iii) to propose a rational approach for designing and putting in place effective mitigation measures. Carbon oxide (CO), nitrogen oxides (NOx), and fine particulate matter (PM10) emissions have been estimated by applying different models, methodologies and databases, depending on the construction process under analysis, and an emissive balance sheet has been produced. Results showed that CO is the pollutant released in the greatest quantity, followed by NOx. The emission of PM10, mainly due to the movement of trucks on unpaved roads, is one order of magnitude less with respect to CO and NOx, but produces the most perceived and undesired effects of the construction process in the interested communities. Tunnels and bridge are the components of a road with the greatest impact in terms of air emissions.

Nick Thom, Novel performance-based technique for predicting maintenance strategy of bitumen stabilised ballast, Construction and Novel performance-based technique for predicting maintenance strategy of bitumen stabilised ballast Abstract Despite being the most used worldwide, railway ballasted tracks presents high maintenance cost related to ballast settlement and particle degradation. With the aim of reducing life cycle costs, bitumen stabilised ballast (BSB) has been recently proposed as a relatively cheap alternative maintenance solution to be applied to existing tracks. This study aims at assessing the potential advantages of this technology, defining a novel maintenance strategy of traditional ballasted trackbeds. A protocol for the application of the BSB technology and its associated maintenance strategy is defined. To estimate minor and major maintenance operations of BSB scenario in comparison to traditional ballasted track-bed, an integrated model, based on laboratory tests, combining the evolution of track irregularities and ballast contamination with traffic, was used. Results together with a sensitivity analysis related to main parameters adopted revealed that the application of BSB is expected to provide a significant increase of intervals between both minor and major maintenance activities.

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Reducing ground borne vibrations in urban areas is a very challenging task in railway transportation. Many mitigation measures can be considered and applied; among these open trenches are very effective. This paper deals with the study of the effect, in terms of reduction of vertical and horizontal displacements and velocities, of the open trenches. 2D FEM simulations have been performed and several open trench configurations have been analysed varying the main geometric features such as width and depth, distance from the rail, thickness of the soil layer over the rigid bedrock, type of the ground, ratio between the depth of the trench, and the thickness of the soil layer. For quantifying the influence of the above specified parameters in reducing ground-borne vibrations an analysis using artificial neural networks (ANNs) has been carried out. Results show that among the geometric parameters the role of the depth of the trench is very significant; however the influence of the depth must be also evaluated in relation to the thickness of the soil layer.