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  • 1.
    Das, Prabir Kumar
    et al.
    KTH Royal Institute of Technology, Sweden.
    Kringos, Niki
    KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Birgisson, Björn
    KTH Royal Institute of Technology, Sweden.
    Micromechanical investigation of phase separation in bitumen by combining atomic force microscopy with differential scanning calorimetry results2013In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, no Suppl 1, p. 25-37Article in journal (Refereed)
    Abstract [en]

    The thermo-rheological behaviour of bitumen depends largely on its chemical structure and intermolecular microstructures. Bitumen is a complex mixture of organic molecules of different sizes and polarities for which the micro-structural knowledge is still rather incomplete. Knowledge at that level can have great implications for behaviour at a larger scale and will help to optimise the bitumen in its production stage. The present study is focused on understanding the fundamental mechanisms behind the micro-structural phase appearance and the speed or mobility at which they change. To do so, atomic force microscopy was utilised at different temperatures to investigate the phase separation behaviour for four different types of bitumen and co-relate it with the differential scanning calorimetry measurements. Based on the experimental evidences, it was found that the observed phase separation is mainly due to the wax/paraffin fraction presence in bitumen and that the investigated bitumen behaves quite differently. Recommendations are made to continue this research into qualitative information to be used on the asphalt mix design level.

  • 2.
    Eriksson, Mimmi
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden; CR Colloidal Resource AB, Sweden.
    Claesson, Per M.
    KTH Royal Institute of Technology, Sweden.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Tuominen, Mikko
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Kappl, Michael
    Nordtreat Oy, Finland.
    Teisala, Hannu
    Max Planck Institute, Germany; Amcor Flexibles Valkeakoski Oy, Finland.
    Vollmer, Doris
    Max Planck Institute, Germany.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick A.C.
    University of Belgrade, Serbia; Aalto University, Finland.
    Mäkelä, Jyrki M.
    Tampere University, Finland.
    Swerin, Agne
    KTH Royal Institute of Technology, Sweden; Karlstad University, Sweden.
    Effects of Gas Layer Thickness on Capillary Interactions at Superhydrophobic Surfaces2024In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 40, no 9, p. 4801-4810Article in journal (Refereed)
    Abstract [en]

    Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth. © 2024 The Authors.

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  • 3.
    Eriksson, Mimmi
    et al.
    RISE Research Institutes of Sweden. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M
    KTH Royal Institute of Technology, Sweden.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Tuominen, Mikko
    RISE Research Institutes of Sweden.
    Kappl, Michael
    Max Planck Institute, Germany.
    Teisala, Hannu
    Max Planck Institute, Germany.
    Vollmer, Doris
    Max Planck Institute, Germany.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick
    Aalto University, Finland; University of Belgrade, Serbia.
    Mäkelä, Jyrki
    Tampere University, Finland.
    Swerin, Agne
    KTH Royal Institute of Technology, Sweden; Karlstad University, Sweden.
    Effects of liquid surface tension on gas capillaries and capillary forces at superamphiphobic surfaces2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 6794Article in journal (Refereed)
    Abstract [en]

    The formation of a bridging gas capillary between superhydrophobic surfaces in water gives rise to strongly attractive interactions ranging up to several micrometers on separation. However, most liquids used in materials research are oil-based or contain surfactants. Superamphiphobic surfaces repel both water and low-surface-tension liquids. To control the interactions between a superamphiphobic surface and a particle, it needs to be resolved whether and how gas capillaries form in non-polar and low-surface-tension liquids. Such insight will aid advanced functional materials development. Here, we combine laser scanning confocal imaging and colloidal probe atomic force microscopy to elucidate the interaction between a superamphiphobic surface and a hydrophobic microparticle in three liquids with different surface tensions: water (73 mN m−1), ethylene glycol (48 mN m−1) and hexadecane (27 mN m−1). We show that bridging gas capillaries are formed in all three liquids. Force-distance curves between the superamphiphobic surface and the particle reveal strong attractive interactions, where the range and magnitude decrease with liquid surface tension. Comparison of free energy calculations based on the capillary menisci shapes and the force measurements suggest that under our dynamic measurements the gas pressure in the capillary is slightly below ambient. © 2023, The Author(s).

  • 4.
    Eriksson, Mimmi
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Claesson, Per Martin
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Järn, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Tuominen, Mikko
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Wallqvist, Viveca
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick A C
    Aalto University, Finland.
    Swerin, Agne
    KTH Royal Institute of Technology, Sweden.
    Wetting Transition on Liquid-Repellent Surfaces Probed by Surface Force Measurements and Confocal Imaging.2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 41, p. 13275-13285Article in journal (Refereed)
    Abstract [en]

    Superhydrophobic surfaces in the Cassie-Baxter wetting state retain an air layer at the surface which prevents liquid water from reaching into the porous surface structure. In this work we explore how addition of ethanol, which reduces the surface tension, influences the wetting properties of superhydrophobic and smooth hydrophobic surfaces. Wetting properties are measured by dynamic contact angles, and the air layer at the superhydrophobic surface is visualized by laser scanning confocal microscopy. Colloidal probe atomic force microscopy measurements between a hydrophobic microsphere and the macroscopic surfaces showed that the presence of ethanol strongly affects the interaction forces. When the macroscopic surface is superhydrophobic, attractive forces extending up to a few micrometers are observed on retraction in water and in 20 vol % ethanol, signifying the presence of a large and growing gas capillary. Submicrometer attractive forces are observed between the probe particle and a smooth hydrophobic surface, and in this case a smaller gas capillary is formed. Addition of ethanol results in markedly different effects between superhydrophobic and hydrophobic surfaces. In particular, we show that the receding contact angle on the superhydrophobic surface is of paramount importance for describing the interaction forces.

  • 5.
    Eriksson, Mimmi
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Tuominen, Mikko
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Järn, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Claesson, Per Martin
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Butt, Hans-Jürgen
    Max Planck Institute for Polymer Research, Germany.
    Vollmer, Doris
    Max Planck Institute for Polymer Research, Germany.
    Kappl, Michael
    Max Planck Institute for Polymer Research, Germany.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick A C
    Omya International AG, Switzerland.
    Teisala, Hannu
    Aalto University, Finland.
    Swerin, Agne
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Direct Observation of Gas Meniscus Formation on a Superhydrophobic Surface2019In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 13, no 2, p. 2246-2252Article in journal (Refereed)
    Abstract [en]

    The formation of a bridging gas meniscus via cavitation or nanobubbles is considered the most likely origin of the submicrometer long-range attractive forces measured between hydrophobic surfaces in aqueous solution. However, the dynamics of the formation and evolution of the gas meniscus is still under debate, in particular, in the presence of a thin air layer on a superhydrophobic surface. On superhydrophobic surfaces the range can even exceed 10 μm. Here, we report microscopic images of the formation and growth of a gas meniscus during force measurements between a superhydrophobic surface and a hydrophobic microsphere immersed in water. This is achieved by combining laser scanning confocal microscopy and colloidal probe atomic force microscopy. The configuration allows determination of the volume and shape of the meniscus, together with direct calculation of the Young-Laplace capillary pressure. The long-range attractive interactions acting on separation are due to meniscus formation and volume growth as air is transported from the surface layer.

  • 6.
    Janhäll, Sara
    et al.
    RISE Research Institutes of Sweden, Built Environment, Energy and Resources.
    Strandberg, Bo
    Lund University, Sweden; Region Skåne, Sweden.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Rissler, Jenny
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. Lund University, Sweden.
    A new method and first results for comparing emissions of fumes during construction of asphalt surfaces2024In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 422, article id 135736Article in journal (Refereed)
    Abstract [en]

    A novel laboratory methodology for analysing hot asphalt fumes from various paving materials is presented and evaluated. This method facilitates comparative assessments, aiming to enhance occupational safety for asphalt workers and ensure safe implementation of new paving materials. Comparative analyses of emissions to air were conducted on standard asphalt and rubber-modified asphalt at different temperatures. The temperature significantly influences PAH emissions. Rubber-modified asphalt demonstrated higher PAH emissions at equivalent temperatures compared to standard asphalt, predominantly naphthalene. Even heavier PAHs as benzo(a)pyrene were occasionally high. Notably, at recommended working temperatures the standard asphalt resulted in higher emissions, comprising heavier PAHs compared to rubber asphalt. © 2024 The Authors

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  • 7.
    Kraft, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Rogers, Patrick
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Eriksson Brandels, Alexander
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Gram, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Trädgårdh, Jan
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Experimentalrubber chip concrete mixes for shock absorbent bike lane pavements.2015Conference paper (Refereed)
    Abstract [en]

    In Sweden the amount of cyclists being injured in traffic has increased in recent years. Over 23,000 peopleper annum visit an acute care hospital after being injured whilst cycling. Most bicycle accidents are single“vehicle” accidents (82 %) and the most common collision is with another cyclist. Due to increased healthcare costs and the fact that more city dwelling people choose to cycle instead of going by car - due both tomonetary, environmental and personal health reasons - one is devoted to find solutions to make cyclingsafer. Besides efforts to increase helmet usage among cyclists and safer bike lane design separate from cartraffic, another way to reduce injuries may be achieved by modifying the bike lanes’ properties. This wouldresult in safer cycling and not only reducing non-cranial injuries, but also limit the severity of head injuries forcyclists not wearing a helmet. Thus, the pavement and bicycle lane material must be an efficient absorbentof impact energy. The work here presents efforts on modifying a concrete pavement by replacing coarseaggregates and sand with rubber chips and rubber crumbs to increase the shock absorbent capacity.Altogether, eighteen different mixtures with varying proportions of rubber, cement and sand were preparedand evaluated regarding elastic modulus and compressive strength. A fly-ash cement, microsilica and latexsolution were used in the concrete mixes. From the results obtained the mix with the best impact absorbingproperties, with a low E-modulus and sufficient compressive strength, was chosen for further evaluation.

  • 8.
    Kumar Das, P
    et al.
    KTH Royal Institute of Technology, Sweden.
    Kringos, N
    KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Birgisson, B
    KTH Royal Institute of Technology, Sweden.
    Microscale investigation of thin film surface ageing of bitumen2014In: Journal of Microscopy, ISSN 2050-5698, Vol. 254, no 2, p. 95-107Article in journal (Refereed)
    Abstract [en]

    This paper investigates the mechanism of bitumen surface ageing, which was validated utilizing the atomic force microscopy and the differential scanning calorimetry. To validate the surface ageing, three different types of bitumen with different natural wax content were conditioned in four different modes: both ultraviolet and air, only ultraviolet, only air and without any exposure, for 15 and 30 days. From the atomic force microscopy investigation after 15 and 30 days of conditioning period, it was found that regardless the bitumen type, the percentage of microstructure on the surface reduced with the degree of exposure and time. Comparing all the four different exposures, it was observed that ultraviolet radiation caused more surface ageing than the oxidation. It was also found that the combined effect was not simply a summation or multiplication of the individual effects. The differential scanning calorimetry investigation showed that the amount of crystalline fractions in bitumen remain constant even after the systematic conditioning. Interestingly, during the cooling cycle, crystallization of wax molecules started earlier for the exposed specimens than the without exposed one. The analysis of the obtained results indicated that the ageing created a thin film upon the exposed surface, which acts as a barrier and creates difficulty for the wax induced microstructures to float up at the surface. From the differential scanning calorimetry analysis, it can be concluded that the ageing product induced impurities in the bitumen matrix, which acts as a promoter in the crystallization process.

  • 9.
    Lyne Laurell, Åsa
    et al.
    KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Birgisson, Björn
    KTH Royal Institute of Technology, Sweden.
    Adhesive surface characteristics of bitumen binders investigated by Atomic Force Microscopy2013In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 113, p. 248-256Article in journal (Refereed)
    Abstract [en]

    Bitumen is a complex hydrocarbon whose composition-structure-property relationship is not well-understood. In this paper, microphase-separated topographic morphologies of unaged penetration grade 70/100 bitumen binders have been visualized by means of AFM QNM, and the relationship to local mechanical properties has been demonstrated. AFM QNM is a surface force mapping technique which measures parameters such as topography, adhesion and elastic modulus simultaneously. The resulting data can then be presented as images representing individual or overlaid parameters, e.g. topographic images with an adhesion overlay or topographic images with a modulus overlay. AFM QNM results show that the adhesive forces measured in the region surrounding (peri phase) the periodic topographic features resembling 'bees' (catana phase) and the region in the 'bee' areas are lower than the adhesive force measured in the smooth matrix (para phase). Likewise it was observed that Young's moduli in the region surrounding (peri phase) the 'bees' (catana phase) and in the 'bees' are higher than Young's modulus of the smooth matrix (para phase).

  • 10.
    Lyne Laurell, Åsa
    et al.
    KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Claesson, Per
    RISE, SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Birgisson, Björn
    KTH Royal Institute of Technology, Sweden.
    Surface wrinkling: The phenomenon causing bees in bitumen2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 20, p. 6970-6976Article in journal (Refereed)
    Abstract [en]

    The so called "bee phenomenon" in bitumen has been investigated by means of AFM quantitative nanomechanical property mapping. Bees are a phenomenon that can be observed by topography measurements using AFM. The characteristic "bee" appearance comes from regions with alternating higher and lower bands in the surface topography of bitumen, which are surrounded by a flat area. The proposed mechanism for bee formation is phase separation and differential contraction during cooling from melt temperatures leading to wrinkling due to differences in the elastic modulus of the material phases. Using a laminate wrinkling model, the thickness of the bee laminate was calculated from the wavelengths and Young's moduli of the bee laminate and the matrix. It was found to vary between 70 and 140 nm for the five bitumen samples that contained significant amounts of wax.

  • 11.
    Makoundou, Christina
    et al.
    University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    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 approaches2021In: Recycling, E-ISSN 2313-4321, Vol. 6, no 1, article id 19Article in journal (Refereed)
    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.

  • 12.
    Makoundou, Christina
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Rubber- and emulsion-based impact-absorbing paving material produced with cold and dry processes: Laboratory and in-situ study2023In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 408, article id 133496Article in journal (Refereed)
    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. 

  • 13.
    Makoundou, Christina
    et al.
    University of Bologna, Italy.
    Sangiorgi, Cesare
    University of Bologna, Italy.
    Johansson, Kenth
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Development of functional rubber-based impact-absorbing pavements for cyclist and pedestrian injury reduction2021In: Sustainability, E-ISSN 2071-1050, Vol. 13, no 20, article id 11283Article in journal (Refereed)
    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.

  • 14.
    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, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    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 study2022In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 23, no 5, p. 315-320Article in journal (Refereed)
    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). 

  • 15.
    Skedung, Lisa
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Collier, Elizabeth S
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Harris, Kathryn L
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Nyhus, Anne Kari
    Microbeads, Norway.
    Björndal, Lene
    Microbeads, Norway.
    FINE-TUNING THE TACTILE PERCEPTION OF COATINGS2021In: European Coatings Journal, ISSN 0930-3847, Vol. 6, p. 32-37Article in journal (Other academic)
    Abstract [en]

    Human tactile evaluations were combined with tactile friction measurements to quantify the perceptual experience of touching coated panels. Monosized beads of nine different polymer compositions were added to a soft-touch waterborne two-component PUR coating. Introducing beads of different composition affected tactile perception.

  • 16.
    Wallqvist, Viveca
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials.
    Kjell, Gunnar B.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Cupina, Ena
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials. Chalmers Univeristy of technology, Sweden.
    Kraft, Lars
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Deck, Caroline
    University of Strasbourg, France.
    Willinger, Rémy
    University of Strasbourg, France.
    New functional pavements for pedestrians and cyclists2017In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 105, p. 52-63Article in journal (Refereed)
    Abstract [en]

    When many fields of pedestrian and cyclist safety have been extensively studied, the surfacing has long been left unquestioned, despite being developed for another mode of transport and being one of the main causes for falls and fall injuries. In this project new surfacing materials for pedestrian and cyclist safety have been produced. Focusing on augmenting previously largely disregarded parameters as impact absorption, comfort and visibility at the same time as avoiding deteriorating of crucial parameters as friction and wear resistance. Rubber content, binder type, and pigment addition have been varied and evaluated. The results demonstrate that by increasing rubber content of the mixtures the head injury criterion (HIC) value and injury risk can be decreased while maintaining frictional properties according to existing criteria. Assembly of test-lanes demonstrate that some developed materials experience lower flow and component separation than standard materials due to rubber addition, calling for further optimisation of construction procedure linked to content development. Initial trials on the test-lanes indicate that a polyurethane (PU) based material has high cycling comfort, visibility and can be modified with phosphorescence properties. For standard asphalt, impact absorption might be inflicted by modification of bitumen alone but is mostly augmented by rubber addition. The results also indicate that rubber content can decrease ice formation on the materials.

  • 17.
    Wojas, Natalia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    Dobryden, Illia
    KTH Royal Institute of Technology, Sweden; Luleå University of Technology, Sweden.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Swerin, Agne
    Karlstad University, Sweden.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick A C
    Aalto University, Finland.
    Claesson, Per M
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor2021In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, no 32, p. 9826-9837Article in journal (Refereed)
    Abstract [en]

    Understanding the wear of mineral fillers is crucial for controlling industrial processes, and in the present work, we examine the wear resistance and nanomech. properties of bare calcite and stearic acid-modified calcite surfaces under dry and humid conditions at the nanoscale. Measurements under different loads allow us to probe the situation in the absence and presence of abrasive wear. The sliding motion is in general characterized by irregular stick-slip events that at higher loads lead to abrasion of the brittle calcite surface. Bare calcite is hydrophilic, and under humid conditions, a thin water layer is present on the surface. This water layer does not affect the friction force. However, it slightly decreases the wear depth and strongly influences the distribution of wear particles. In contrast, stearic acid-modified surfaces are hydrophobic. Nevertheless, humidity affects the wear characteristics by decreasing the binding strength of stearic acid at higher humidity. A complete monolayer coverage of calcite by stearic acid results in a significant reduction in wear but only a moderate reduction in friction forces at low humidity and no reduction at 75% relative humidity (RH). Thus, our data suggest that the wear reduction does not result from a lowering of the friction force but rather from an increased ductility of the surface region as offered by the stearic acid layer. An incomplete monolayer of stearic acid on the calcite surface provides no reduction in wear regardless of the RH investigated. Clearly, the wear properties of modified calcite surfaces depend crucially on the packing d. of the surface modifier and also on the air humidity.

  • 18.
    Wojas, Natalia
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Swerin, Agne
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Wallqvist, Viveca
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Järn, Mikael
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. Omya International AG, Switzerland.
    Schoelkopf, Joachim
    Omya International AG, Switzerland; Aalto University, Finland.
    Gane, Patrick
    Claesson, Per M.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Iceland spar calcite: Humidity and time effects on surface properties and their reversibility2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 541, p. 42-55Article in journal (Refereed)
    Abstract [en]

    Understanding the complex and dynamic nature of calcite surfaces under ambient conditions is important for optimizing industrial applications. It is essential to identify processes, their reversibility, and the relevant properties of CaCO3 solid-liquid and solid-gas interfaces under different environmental conditions, such as at increased relative humidity (RH). This work elucidates changes in surface properties on freshly cleaved calcite (topography, wettability and surface forces) as a function of time (≤28 h) at controlled humidity (≤3–95 %RH) and temperature (25.5 °C), evaluated with atomic force microscopy (AFM) and contact angle techniques. In the presence of humidity, the wettability decreased, liquid water capillary forces dominated over van der Waals forces, and surface domains, such as hillocks, height about 7.0 Å, and trenches, depth about −3.5 Å, appeared and grew primarily in lateral dimensions. Hillocks demonstrated lower adhesion and higher deformation in AFM experiments. We propose that the growing surface domains were formed by ion dissolution and diffusion followed by formation of hydrated salt of CaCO3. Upon drying, the height of the hillocks decreased by about 50% suggesting their alteration into dehydrated or less hydrated CaCO3. However, the process was not entirely reversible and crystallization of new domains continued at a reduced rate.

  • 19.
    Wojas, Natalia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    Swerin, Agne
    Karlstad University, Sweden.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Schoelkopf, Joachim
    Omya International Ag, Switzerland.
    Gane, Patrick
    Aalto University, Finland.
    Claesson, Per M
    KTH Royal Institute of Technology, Sweden.
    Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization2021In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, no 48, p. 14135-Article in journal (Refereed)
    Abstract [en]

    A profound understanding of the properties of unmodified and saturated fatty acid-modified calcite surfaces is essential for elucidating their resistance and stability in the presence of water droplets. Additional insights can be obtained by also studying the effects of carboxylic acid-saturated aqueous solutions. We elucidate surface wettability, structure, and nanomechanical properties beneath and at the edge of a deposited droplet after its evaporation. When calcite was coated by a highly packed monolayer of stearic acid, a hydrophilic region was found at the three-phase contact line. In atomic force microscopy mapping, this region is characterized by low adhesion and a topographical hillock. The surface that previously was covered by the droplet demonstrated a patchy structure of about 6 nm height, implying stearic acid reorganization into a patchy bilayer-like structure. Our data suggest that during droplet reverse dispensing and droplet evaporation, pinning of the three-phase contact line leads to the transport of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules to the contact line boundary. Compared to the surface of intrinsically hydrophobic materials, such as polystyrene, the changes in contact angle and base diameter during droplet evaporation on stearic acid-modified calcite are strikingly different. This difference is due to stearic acid reorganization on the surface and transport to the water-air interface of the droplet. An effect of the evaporating droplet is also observed on unmodified calcite due to dissolution and recrystallization of the calcite surface in the presence of water. In the case where a water droplet saturated with octanoic acid is used instead of water, the stearic acid-coated calcite remains considerably more stable. Our findings are discussed in terms of the coffee-ring effect. © 2021 The Authors. 

  • 20.
    Wojas, Natalia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    Tyrode, Eric
    KTH Royal Institute of Technology, Sweden.
    Corkery, Robert
    KTH Royal Institute of Technology, Sweden; Australian National University Department of Applied Mathematics, Australia.
    Ernstsson, Marie
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallqvist, Viveca
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Swerin, Agne
    Karlstad University, Sweden.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick A C
    Aalto University, Finland; University of Belgrade, Serbia.
    Claesson, Per M.
    KTH Royal Institute of Technology, Sweden.
    Calcite Surfaces Modified with Carboxylic Acids (C2 to C18): Layer Organization, Wettability, Stability, and Molecular Structural Properties2023In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 39, no 42, p. 14840-14852Article in journal (Refereed)
    Abstract [en]

    A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over the production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapor deposition. The properties of the resulting carboxylic acid layers were analyzed using surface-sensitive techniques, such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS), and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids such as stearic acid. The stearic acid layer formed by vapor deposition is initially patchy, but with increasing vapor exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly at higher temperatures due to the higher vapor pressure. The stability of the deposited fatty acid layer in the presence of a water droplet increases with the chain length and packing density in the adsorbed layer. Vibrational sum frequency spectroscopy data demonstrate that the stearic acid monolayers on calcite have their alkyl chains in an all-trans conformation and are anisotropically distributed on the plane of the surface, forming epitaxial monolayers. Vibrational spectra also show that the stearic acid molecules interact with the calcite surface through the carboxylic acid headgroup in both its protonated and deprotonated forms. The results presented provide new molecular insights into the properties of adsorbed carboxylic acid layers on calcite.

  • 21.
    Álvarez-Asencio, Rubén
    et al.
    KTH Royal Institute of Technology, Sweden; IMDEA Nanoscience, Spain.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kjellin, Mikael
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, Sweden.
    Camacho, Alejandra
    L’Oréal Research and Innovation, US.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Luengo, Gustavo S.
    L’Oréal Research and Innovation, France.
    Nanomechanical properties of human skin and introduction of a novel hair indenter2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, p. 185-193Article in journal (Refereed)
    Abstract [en]

    The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

1 - 21 of 21
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