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  • 1.
    Makoundou, Christina
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. University of Bologna, Italy.
    Fathollahi, Alireza
    Coventry University, UK; University of Strathclyde, UK.
    Kleiven, Svein
    KTH Royal Institute of Technology, Sweden.
    Coupe, Stephen
    Coventry University, UK.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Mechanical and leaching characterisation of impact-absorbing rubberised asphalts for urban pavements2023Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 56, nr 3, artikel-id 55Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new impact-absorbing material is being developed to protect vulnerable road users in urban areas and has been produced and tested, mechanically and environmentally in the laboratory. The main constituent of this innovative material is the rubber recycled from end-of-life tyres to foster a circular use of resources and exploit rubber’s elastic properties. The study aims to provide a complete Uniaxial Compression Test (UCT) and leaching analysis of the material to propose and optimise a mix that is mechanically sound, durable, and respectful of the environment, in view of in-situ applications. Therefore, the UCT and Dynamic Surface Leaching Test (DSLT) were carried out on rubberised asphalt specimens with different mix designs. The 64 days cumulative concentrations of leached heavy metals and trace elements from unit surface of specimens were calculated and quantified, according to the CEN/TS 16637 standard. In parallel, thanks to a specific mechanical characterisation, compressive stress–strain curves were obtained, and the relaxation and elastic modulus were evaluated. The results from the compression tests showed that the A-mixes have the best elastic and absorbing behaviour, especially those made with an SBS-modified bituminous emulsion (A4). The results from DSLT showed that the cumulative concentration of released elements, per unit surface of specimens were lower than the Dutch Soil Quality Decree (SQD) thresholds, taken as a reference. The low and early release of leachant observed for the mixtures, especially A4 as the most promising one, leave the possibility to handle the leaching with several solutions, including rubber coating treatment or water washing before their incorporation into the mix to limit and prevent their leaching while permitting very high injury reduction performances. © 2023, The Author(s).

  • 2.
    Makoundou, Christina
    et al.
    University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Functionalization of crumb rubber surface for the incorporation into asphalt layers of reduced stiffness: An overview of existing treatment approaches2021Ingår i: Recycling, E-ISSN 2313-4321, Vol. 6, nr 1, artikel-id 19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The substitution of mineral aggregates with crumb rubber (CR) from waste end‐of‐life tires (ELTs) in the asphalt concretes, has been considered a sustainable paving industry approach. The rubber has been used to construct pavements with proven enhanced resilience and improved durability. However, some issues related to the rubber’s surface adhesion or swelling may arise with these practices and generate complications (binder consumption, temperatures, mixing times). One possible solution to overcome the materials’ compatibility problems is to pre‐treat the CR’s surface before its incorporation into the asphalt mixes to allow a surface functionalization that can enhance coverage and cohesion inside the mixes. The physical treatments using radiations‐based beam are already exploited in the plastic recycling industries avoiding the use of chemicals in con-siderable amounts. Such treatments permit the recovering of large quantities of polymer‐based materials and the enhancement of interfacial properties. This article provides an overview of existing surface treatments of polymers and especially rubber, including gamma ray, UV‐ozone, micro-waves, and plasma. Several studies have shown an overall improvement of the rubber surface’s reactive properties due to contaminant removal or roughness enhancement attributed to cross‐link-ing or scission reactions occurring on the rubber’s surface layer. With those properties, the asphalt mixes’ phase stability properties are increased when the pre‐treated rubber is incorporated. The treatments would permit to increase the CR quantities, yet reduce the layer stiffness, and improve the durability and the sustainability of future advanced road pavements. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

  • 3.
    Makoundou, Christina
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Rubber- and emulsion-based impact-absorbing paving material produced with cold and dry processes: Laboratory and in-situ study2023Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 408, artikel-id 133496Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Impact-absorbing pavements (IAPs) may be used as novel sidewalks and bike lanes surface layers to decrease fall-related injuries among vulnerable road users (VRUs). Therefore, a cold-made, highly rubberised asphalt mixture (56% recycled rubber in the total volume of the mix) was developed in the laboratory, and the process was then upscaled, permitting its construction on a trial site. Both laboratory and on-site tests facilitated the evaluation of the material’s mechanical properties, impact-absorption capabilities, and frictional behaviour. The field trial enabled a comprehensive assessment of the material’s performance after six months of usage by pedestrians and cyclists on a hybrid segment. Additionally, evaluations were conducted after six, fifteen, and twenty months. The results confirmed the possibility to produce and lay a cold, highly rubberised paving material with valuable impact-attenuation performances. The mechanical analysis has shown the material’s elastic behaviour and its capability to carry uniaxial compression stress leading to a 5% strain of the total height without losing its properties. Furthermore, the critical fall height (CFH) values exhibited a sixfold increase compared to conventional asphalt, thereby reducing the severity of potential injuries. In terms of durability, the pavement’s overall effectiveness remained significant even after six, fifteen, and twenty months of use. The study demonstrated the capability to cover and fill holes and damaged portions using the same rubberised and cold mixture, a crucial aspect concerning the material’s future and maintenance considerations. 

  • 4.
    Makoundou, Christina
    et al.
    University of Bologna, Italy.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Development of functional rubber-based impact-absorbing pavements for cyclist and pedestrian injury reduction2021Ingår i: Sustainability, E-ISSN 2071-1050, Vol. 13, nr 20, artikel-id 11283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclists, pedestrians and elderly people’s specific needs in urban road infrastructures are often neglected. They rarely benefit from safety measures or innovations. Inspired by playgrounds and aiming to reduce vulnerable road users (VRUs) injuries, the development of the rubber-based Impact-Absorbing Pavements (IAP) offers a possibility to rethink the design of urban pavements and address safety on roads, which constitutes a major challenge in terms of attaining more sustain-able, resilient, and safe cities. Therefore, bituminous mixtures with four different crumb rubber con-tents, 0%, 14%, 28%, and 33% (in total weight), were produced by partial aggregates substitution using the dry process. After the assessment of the geometrical and volumetric properties, the mechanical performances were evaluated. Finally, the samples were tested to measure the abrasion and impact attenuation with the well-known Head Injury Criterion (HIC), at different temperatures from −10 to 40 °C, to obtain a wide range of values referring to possible weather conditions. A significant effect of the rubber percentage and layer thickness on impact attenuation was observed. All observations and results confirm the feasibility of the IAP concept and its positive effect on future injury-prevention applications. © 2021 by the authors.

  • 5.
    Sahandifar, P.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Makoundou, Christina
    University of Bologna, Italy.
    Fahlstedt, M.
    KTH Royal Institute of Technology, Sweden.
    Sangiorgi, C.
    University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Kleiven, S.
    KTH Royal Institute of Technology, Sweden.
    A rubberized impact absorbing pavement can reduce the head injury risk in vulnerable road users: A bicycle and a pedestrian accident case study2022Ingår i: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 23, nr 5, s. 315-320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: Vulnerable Road Users (VRU), including pedestrians and cyclists, are generally the least protected road users and are frequently missed in the planning process of preventive measures. Rubberized asphalt mixtures were originally developed as a possible environmentally friendly solution to recycle the End-of-Life Tires while making the pavements more durable. The objective of the current study was to explore the effects of increasing the rubber content of the common rubberized asphalt mixtures in reducing the head injuries risk for VRUs. Method: To achieve this purpose, four different sample series with 0, 14, 28, and 33 weight percent rubber in each were tested. A compressive test without permanent deformation and one with failure were performed on each sample series. The mechanical behavior of each set was modeled using a MAT_SIMPLIFIED_RUBBER material model in LS-Dyna and validated against a standard Head Injury Criterion (HIC) drop test. Ultimately, previously low-speed accident reconstructed cases, a bicycle and a pedestrian one, were used to assess the effect of varying the rubber content on reducing the head injury risk. Results: In the bicycle accident case, the risk of skull fracture was reduced from 0.99 to 0.29 when comparing the non-rubberized asphalt mixture with the 33% rubber mixture. In the same accident case, the risk of concussion, evaluated using the logistic regression method, was reduced from 0.97 in the non-rubberized mixture to 0.81 in the 33% rubber mixture. The initial conditions, linear and rotational velocities, were lower for the pedestrian case compared to the bicycle case (the bicycle case was more severe compared to the pedestrian case), which led to lower strains in the pedestrian case. In the pedestrian accident case, the risk of skull fracture was reduced from 1.00 in the non-rubberized mixture to 0.63 in the 33% rubber mixture, while the risk of concussion was reduced from 0.64 to 0.07. Conclusion: The rubberized asphalt mixtures could reduce the head injury risk for the studied cases when the rubber content in the asphalt mixture increases. © 2022 The Author(s). 

  • 6.
    Siverio Lima, M S
    et al.
    University of Innsbruck, Austria.
    Makoundou, Christina
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Sangiorgi, Cecare
    University of Bologna, Italy.
    Gschösser, F.
    University of Innsbruck, Austria.
    Life Cycle Assessment of Innovative Asphalt Mixtures Made with Crumb Rubber for Impact-Absorbing Pavements2022Ingår i: Sustainability, E-ISSN 2071-1050, Vol. 14, nr 22, artikel-id 14798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study applies the life cycle assessment methodology to evaluate the environmental impacts of shock-absorbing pavements fabricated with recycled materials (crumb rubber and a colored pigment called ferrotone), employing the “cradle-to-grave” approach, in which the impacts of all life cycle phases (from materials’ acquisition to the end-of-life of the pavement) are included. The analysis compares the impacts of standard and innovative asphalt materials, considering cold and hot production processes. In addition, three different lifespans are simulated for the pavement structures: the reference service life until the first intervention is considered to be 5 years, and the following scenarios consider that the alternative asphalt materials may last 20% less (4 years) or 20% longer (6 years) than the reference service life. The analysis uses non-renewable cumulative energy demand (nr-CED) and global warming potential (GWP) as main indicators to determine the environmental impacts over a 45-year analysis period. The results show that adopting the “dry process” (consisting of adding the rubber as a partial substitution for aggregates) increases the overall impacts due to the need for higher contents of binder. However, if the alternative pavement structures last 20% longer than the reference, they would generate lower impacts in terms of nr-CED and GWP. © 2022 by the authors.

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