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  • 51.
    Hailesilassie, Biruk W.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Hugener, Martin
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Influence of foaming water content on foam asphalt mixtures2015Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 85, s. 65-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Warm mix asphalt technology using foamed bitumen is being used widely despite the fact that high air void content and poor coating of large aggregate remain major drawbacks require enhancement. This paper manly focuses on the investigation of water content influence on the foamed bitumen and the asphalt mixture. Influence of the water content in combination with compaction temperature has been investigated using gyratory compaction method. AC11N foam asphalt mixture is produced in the lab using lab foamer. Marshall stability and indirect tensile test was used to evaluate the foam asphalt mixture performance. The investigation revealed that the Marshall stability of foam asphalt mixture is highly influenced by compaction temperature compared to water content. Moreover, increasing the water content helps in coating large aggregates when the mixture is produced at low temperature, nevertheless using high water content reduces the Marshall stability to certain extent. In addition the amount of water trapped in the mixture after the mixing process was determined using thermogravimetric analysis. The amount of water remaining in the asphalt mixture is less than 1% relative to the bitumen mass.

  • 52.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Hugener, M.
    Bieder, A.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. EMPA, Swiss Federal Laboratories for Material Science and Technology, Switzerland.
    New experimental methods for characterizing formation and decay of foam bitumen2015Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this research, new experimental tools were applied for characterizing the bitumen foam during the foaming process. Ultrasonic sensors were used for accurately monitoring the expansion and decay of foam bitumen as a function of time. Assessment of foam bitumen viscosity was performed using high frequency torsional rheometer and in situ observation by X-ray radiography. A high-speed camera was applied for examining the foam bitumen stream right at the nozzle revealing that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. Moreover, infrared thermal images were taken for obtaining information on the in situ surface temperature of foam bitumen during the hot foaming process. The result showed that the average surface temperature of foam bitumen depends on the water content of the bitumen and bubble size distribution, 108 and 126 °C for 4 and 1 wt% (by weight) water content respectively. The residual water content in the decaying foam bitumen was determined by thermogravimetric analysis. The result demonstrated that residual water content depends on the initial water content, and was found to be between 38 and 48 wt% of the initial water content of 4–6 wt%. Finally, X-ray computed tomography was applied for examining the decay of foam bitumen revealing that the bubbles of foam bitumen remain trapped close to the surface of the foam bitumen.

  • 53.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Jerjen, I.
    Griffa, M.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland .
    A closer scientific look at foam bitumen2017Ingår i: Road Materials and Pavement Design, ISSN 1468-0629, Vol. 18, nr 2, s. 362-375Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the asphalt industry, a substantial interest is observed to find possibilities to reduce the production temperature of asphalt mixtures. In the context of this research, new methods for the visualisation of unstable bitumen foam, such as dynamic X-ray radiography, computed tomography (CT) and high-speed camera investigations, have been developed. Moreover, characterisation with empirical methods such as expansion ratio and half-life was determined accurately using ultrasonic measurements. This opens new possibilities to characterise bitumen foam (foaming process) for practical applications. Examination of the foam bitumen stream using a high-speed camera revealed that the foam bitumen contains fragmented pieces of bitumen, which resemble more a liquid than foam. This indicates that the foam is formed afterwards and not, as assumed, within the expansion chamber of the foam generator. In situ thermal imagery of the surface, during the hot foaming process, showed that the temperature distribution depends on the foaming water content (W.C.) and bubble size distribution. Higher W.C. results in more inhomogeneous temperature distribution as compared to lower W.C. (<2 wt%). The dynamic X-radiography results indicated that as the foam decays, the bubble size distribution becomes progressively larger with time for 160°C bitumen temperature. Furthermore, at the beginning of the foam formation, majority of the bubbles is small in cross-section size (0.2–10 mm2). At a later stage, the bubbles become polydisperse. Moreover, theoretical investigations based on the 3D X-ray CT scan data set of bubble merging show that the disjoining pressure increases as the foam film gets thinner with time and finally undergoes rupture. The speed of the bubbles also increases with time when the bubbles are getting closer to each other.

  • 54.
    Hallberg, Daniel
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Development and adaption of a life cycle management system for construction works2005Ingår i: Proceedings of the International workshop on Lifetime Engineering of Civil Infrastructure: honouring the career of Professor Asko Sarja, 2005Konferensbidrag (Refereegranskat)
  • 55.
    Hallberg, Daniel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Akander, J.
    Stojanovic, Bojan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Kedbäck, M.
    Life Cycle Management System: A planning tool supporting Long-term based design and maintenance planning2008Ingår i: 11th International Conference on Durability of Building Materials and Components, 2008Konferensbidrag (Refereegranskat)
  • 56.
    Hallberg, Daniel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Stojanovic, Bojan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Akander, Jan
    (University of Gävle, Department of Technology and Built Environment.
    Långsiktig underhållsplanering av fjärrvärmenät: En förstudie av möjligheter till utveckling av LMS2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    amtidigt som fjärrvärme är ett effektivt sätt att leverera värme så leder en centraliserad värmeproduktion till att fler personer drabbas vid eventuella driftavbrott. Detta skapar ett behov av ökad leveranssäkerhet och kontroll av prestanda över hela fjärrvärmenätets livscykel. Genom en långsiktig planering av nätets utbyggnad och förvaltning erhålls effektivare resursanvändande och större säkerhetsmarginaler. Långsiktig planering bygger till stor del på analys av olika scenarier där såväl rådande förutsättningar som ”worst cases” kan beaktas utifrån olika aspekter (tekniska, ekonomiska, säkerhetsmässiga m.m.). Målet är att hitta optimerade åtgärder, vilket kräver systematisk hantering och bearbetning av en stor mängd information. Detta kan endast göras rationellt med hjälp av IT-verktyg. Life cycle Management System (LMS) är ett resultat av tre konsekutiva EU-finansierade forskningsprojekt där gruppen för byggnadsmaterialteknik – Högskolan i Gävle, har haft en ledande roll. Systemet innehåller utvecklade rutiner och metoder för hantering av information som ligger till grund för långsiktig planering och optimerad förvaltning av byggnadsverk. Systemmässigt är LMS uppbyggt av moduler som hanterar och analyserar data på olika sätt. Anledningen till systemets modulbaserade struktur är att det, helt eller i delar, kan anpassas mot de krav och önskemål som klienten ställer på systemet. På så sätt behöver klienten bara komplettera sitt befintliga system med de funktioner som önskas av LMS, samtidigt som denne undviker att ”kasta ut” det gamla systemet. Förstudien omfattar en litteraturstudie och analys av Gävle Energi AB:s (GEAB) drift- och underhållsdata. Förstudiens syfte är att identifiera och kartlägga de anpassnings- och utvecklingsbehov som föreligger en implementering av LMS som planeringsverktyg för GEAB:s fjärrvärmenät.

  • 57.
    Hameury, Stéphane
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Influence of coating system on the moisture buffering capacity of panels of Pinus sylvestris L2007Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 2, nr 3-4, s. 97-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The indoor relative humidity in dwellings and offices is an important factor in building physics. The ability of hygroscopic materials and especially wood materials to store and release moisture helps to regulate the indoor climate naturally and to avoid extremes of humidity. In the present study, cyclic sorption experiments with coated Scots pine were performed. Materials with different coating compositions were exposed to day-to-day relative humidity changes. The moisture buffering capacity was estimated by a gravimetric method and the moisture buffer value was computed. The results show that the coating has a significant impact on the moisture buffering capacity of the underlying Scots pine. The moisture distribution in the wood sample was appraised for each coating system using a proton magnetic resonance imaging technique. This study confirmed that the dynamics of moisture exchange between the indoor environment and the wooden material during typical daily moisture fluctuations is confined to a few millimetres behind the air-wood interface.

  • 58.
    Hameury, Stéphane
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study2005Ingår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, nr 10, s. 1400-1412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper introduces a hygrothermal model accounting for the moisture and heat transport in a massive wood envelope directly exposed to an indoor climate. A better knowledge of the passive interaction between an indoor climate and a heavy timber structure could lead to presenting an alternative to high air exchange rate, and to increasing the thermal comfort of the inhabitants. So far, the model is developed as a stand-alone application with a finite difference method, and is written in a Neutral Model Format, enabling a later implementation in a modular environment for indoor climate energy calculations, called IDA ICE. A numerical simulation is provided to depict the buffering capacity of a massive timber structure as a function of the air exchange rate and the effective wood wall area.

  • 59.
    Hameury, Stéphane
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    The buffering effect of heavy timber constructions on the indoor moisture dynamic2005Ingår i: Proceedings of the Nordic Symposium on Building Physics, Reykjavik, 2005, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since the renewal of the fire regulations in the 90s, an alternative to the traditional light-weight timber frame structures particularly suitable for multi-storey dwellings has recently emerged in the Scandinavian countries under the generic name of massive wood construction or heavy timber construction. This concept provides manifold architectonic possibilities for the use of wood as a building and structural material, with the particularity among others of creating large areas of wood surface being directly exposed into an indoor environment. Regarding the hygroscopic properties of wood materials, this calls upon the possibility of buffering the indoor environment in term of moisture fluctuations by making use of the structure as a passive system. This paper discusses some insights and thoughts round about the notion of moisture buffer capacity through the examination of the indoor moisture dynamic registered into four apartments during the year 2003 at the Vetenskapsstaden multi-storey dwelling located in Stockholm. Numerical results are also provided to ascertain and highlight the holistic approach lying behind this concept where the control of the indoor moisture dynamic requires taking simultaneously into consideration several aspects of the building as the ventilation strategy, the structure configuration, the building use and the outdoor climate.

  • 60.
    Hameury, Stéphane
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Sterley, Magdalena
    Magnetic resonance imaging of moisture distribution in Pinus sylvestris L. exposed to daily indoor relative humidity fluctuations2006Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, Vol. 1, nr 3-4, s. 116-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    n contact with indoor air, wood materials have a high potential passively to reduce the indoor humidity fluctuations resulting from internal moisture loads and outdoor humidity fluctuations. This ability, characterized by the moisture buffering capacity of building materials, has attracted increasing attention within building physics, but a suitable method to appraise and quantify this phenomenon is still sought. In this study, a non-invasive spectroscopic method of accessing information about the interaction between indoor air and Scots pine was investigated. A comprehensive account is given of spatially resolved moisture absorption (desorption) into (from) Scots pine by proton magnetic resonance imaging ([1H]MRI) based on an effective single-point imaging (SPI) sequence. SPI images of bound-water distribution in Scots pine with a spatial resolution on a sub-millimetre scale were acquired when one of the orthotropic directions of the wood material was exposed to typical indoor day-to-day moisture fluctuations. The nuclear magnetic resonance imaging measurements presented in this study clearly show the potential of the method to provide accurate spatial information about the wood-water interaction below the fibre saturation point and hence to characterize the moisture buffering capacity of wood materials.

  • 61.
    Harmachova, Karolina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Vibration performance of hybrid steel-CLT floors2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the light of today’s effort to achieve sustainable future of the planet, timber as building material makes a comeback on the construction market. Since the requirements on the buildings and the internal comfort increase, there is a need for finding new solutions and products; one of them is cross-laminated timber (CLT), which has the potential to be used for high-rise buildings due to its mechanical properties. The aim of this work was to study the vibration performance of CLT floors as it is often the governing factor in design of CLT structures unlike for other common building materials.

    The orthotropic mechanical properties of CLT were determined by the shear analogy method and verified with a finite element (FE) model of a simply supported beam compared to hand calculations of shear forces, bending moments and deflections. The properties based on Timoshenko’s approach were evaluated as less precise regarding the deflection.

    The non-composite structural behaviour of a steel-CLT hybrid floor structure was predicted for FE dynamic analysis based on a comparison between modelling exercise and hand calculations.

    Two different methods, the Concrete Society (SC) and Steel Construction Institution (SCI) methods, both seemed to be applicable for determination of the response factor first since the mechanical properties are not used as input in the calculations. These two methods differ in certain aspects, and based on FE analysis of simply supported slab even the resulting response factor for the CLT differs significantly. Moreover, the hand calculation results were similar to those of the FE analysis for the CS method, but in less agreement for the SCI method. Nevertheless, it is not recommended to reject the latter method based on this study and further studies should be performed on real structures with response factor known from on-site measurements.

    A part of the first floor of Canary Wharf College was modelled and analysed, and previous measurements of the frequency and response factors enabled a validation of some assumptions. The SCI approach showed to be inadequate for this type of structure and therefore only the CS method was applied further. Analysis of the floor structures supported by walls demonstrated similar results from both the measurements and the dynamic analysis. However, if the floor slab was supported by beams, the response factor was significantly overestimated although on the conservative side. This difference suggests that the modelling of such conditions are not satisfactory.

    The CS method appears to assess correctly the magnitude of the response factor for CLT floors supported by walls but overestimates it in case of beam supports. The first finding shall be confirmed through analysis of other structures and a more extensive research should focus on the latter one to determine more exact behaviour of the model under different conditions.

  • 62.
    HELGADÓTTIR, KRISTÍN
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    BJÖRNSDÓTTIR, RAGNHEIÐUR
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    The Nordic Prediction Method For Railway Traffic Noise: Improvements of the current corrections forrailway bridges, switches and crossings2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Railway noise is a very important and growing health hazard in today´s society.Railway systems pass through towns and cities and create noise. When trainsride through or over railway bridges, switches and crossings the noise increasessubstantially, causing great annoyance to the residents in the area.At the present time, acoustic regulations exist in most countries and are set to achievea good environmental quality in residential areas, schools, hospitals, offices andhotels.A few calculation models exist for railway traffic noise, such as The NPM 1996,NORD2000 and Cnossos-EU. The NPM 1996 is currently used in Sweden to calculatenoise propagation from railway traffic. To uphold the regulations set, it is importantthat the method used is as precise as possible. All of these calculation modelsare based on several correction factors. Today, the current corrections for trackconditions, that is railway bridges, switches and crossings, are not very accurate andneed to be reconsidered.The aim of this project was to investigate and quantify the error of the NPM correctionfactors and give some indication of how they should be adjusted. This is done to makethe noise prediction from railway traffic more accurate and thus protect the residentsfrom these health risks.The specific objective was to perform significant amount of field measurements ofnoise from trains on different steel bridges, switches and crossings, as well as on afew concrete bridge according to the measurement standard Nordtest NT 098. Thefield work was carried out over the period March to May, when weather conditionsmet the criteria for field measurements, in and around the Stockholm area.The results obtained revealed that the correction factors for steel bridges andcrossings are considerably lower in the NPM than measured in this project. However,the correction factors for switches and concrete bridges are similar to the ones inthe NPM. In this thesis, a part of the correction factors have only been invalidatedto a degree. It has been shown that each bridge is unique and perhaps there is apossibility of finding similarities between some type of bridges. However, much moreiv |measurements are needed to see any correlation between each bridge type. Thus,further and more comprehensive measurements have to be carried out in order toestablish new accurate correction factors for track conditions in the Nordic PredictionMethod.

  • 63.
    Heydari, Golrokh
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sedighi Moghaddam, Maziar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden.
    Tuominen, Mikko
    Fielden, Matthew
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haapanen, Janne
    Mäkelä, Jyrki M.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wetting hysteresis induced by temperature changes: supercooled water onhydrophobic surfacesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The state and stability of supercooled water on (super)hydrophobic surfaces is crucial for low temperature applications and for obtaining anti-icing and de-icing properties. Surface characteristics such as topography and chemistry are expected to affect wetting hysteresis during temperature cycling experiments, and also the freezing delay of supercooled water. We utilized stochastically rough wood surfaces that were further modified to render them hydrophobic or superhydrophobic. Liquid flame spraying (LFS) was utilized to create a multi-scale roughness by depositing titaniumdioxide nanoparticles. The coating was subsequently made non-polar by applying a thin plasma polymer layer. As flat reference samples modified silica surfaces with similar chemistries were utilized. With these sets of surfaces we test the hypothesis that superhydrophobic surfaces also should retard ice formation. Wetting hysteresis was evaluated using contact angle measurements during a freeze-thaw cycle from room temperature to freezing occurrence at -7 °C, and then back to room temperature. Further, the delay in freezing of supercooled water droplets was studied at temperatures of -4 °C and -7 °C. The hysteresis in contact angle observed during a cooling-heating cycle is found to be small on flat hydrophobic surfaces. However, significant changes in contact angles during a cooling-heating cycle are observed on the rough surfaces, with a higher contact angle observed on cooling compared to during the subsequent heating. This hysteresis is lower for hydrophobic wood samples with multi-scale roughness compared to those with predominantly micro-scale features. Condensation and subsequent frost formation at sub-zero temperatures induce the hysteresis. The freezing delay data suggests that the multi-scale roughness reduces the penetration of supercooled water into surface depressions, and enhances the freezing delay at low degrees of supercooling. However, the flat surface is even more efficient in enhancing the freezing delay than the rougher surfaces, which can be rationalized considering heterogeneous nucleation theory. Thus, our data suggests that molecular flat surfaces, rather than rough superhydrophobic surfaces, are beneficial for retarding ice formation under conditions that allow condensation and frost formation to occur.

  • 64.
    Inoue, Masafumi
    et al.
    University of Tokyo.
    Kawai, Shuichi
    Kyoto University.
    Wålinder, Magnus E. P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rowell, Roger M.
    USDA, Forest Service, Forest Products Laboratory, Madison USA.
    Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame2008Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 3, nr 3-4, s. 119-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160?200°C), pressures (0.5?3 MPa) and hot-pressing times (2?16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.

  • 65.
    Jelagin, Denis
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    AHMED, ABUBEKER
    Lu, Xiaohu
    Said, Safwat F.
    Asphalt layer rutting performance prediction tools2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to creating high maintenance costs, rutting is a major concern for traffic safety, as the rut development increases the risk of hydroplaning and introduce difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. In particular, better rutting performance models are needed to evaluate, new asphalt materials as well as to evaluate the impact of different vehicle types on roads’ service life.The main goal of this report is to present a summary of the existing asphalt rutting performance prediction tools. The present review is limited to available and/or frequently referred to tests and models with an established link to field rutting performance. Accordingly, models focusing solely on permanent deformation on the material level are beyond the framework of the present study.Road structure and its materials, heavy vehicle parameters and climate affecting rutting accumulation in the field are identified. Their significance has been evaluated based on the experimental and numerical findings reported in the literature. Several rutting performance prediction models recently proposed in the literature are summarized along with the material characterization tests used in the models. The reviewed models’ capability to quantify the influence of various structural, material and traffic parameters on the pavement’s rutting performance is examined. It is concluded that implementation of rutting performance models incorporating experimentally measured viscoelastic and permanent deformation properties of asphalt mixtures is a promising way to improve the accuracy of pavement performance predictions. In particular since they allow the effect of novel materials, e.g. polymer-modified, on the pavement’s rutting performance to be quantified.

  • 66.
    Jelagin, Denis
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Saadati, Mahdi
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.). Atlas Copco, Sweden.
    Jerjen, I.
    Larsson, Per-Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Mechanical Characterization of Granite Rock Materials: On the Influence from Pre-Existing Defects2018Ingår i: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 46, nr 2, s. 540-548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The length, orientation, and population of pre-existing cracks play an important role in the mechanical response of quasi-brittle materials, such as granite. Specifically, Bohus granite rock is at issue in the present investigation. The aims of this study are (1) to demonstrate the existence and characteristics of pre-existing defects (cracks) in granite rock specimens, and (2) to determine the influence from these defects at characterization of such materials. In doing so, X-ray tomography was the method used to visualize the cracking of three-point bending specimens in the context of pre-existing defects. It was also the intention to relate the experimentally determined effect of these cracks at three-point bending testing with corresponding results from numerical methods and specifically finite-element calculations. In the latter case, the location of these cracks was of primary interest and it was shown that this feature can be of considerable importance at material characterization.

  • 67. Jeoffroy, E.
    et al.
    Bouville, F.
    Bueno, M.
    Studart, A. R.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Iron-based particles for the magnetically-triggered crack healing of bituminous materials2018Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 164, s. 775-782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bituminous road pavements may suffer from cracking over the years due to repeated stresses. In this study, we compare the effect of different sizes and chemical compositions of magnetically-responsive iron-based particles used as additives to heat up road pavements and thus to close cracks. By applying an alternating magnetic field (AMF), we found that there is an optimal size depending on the particle electrical conductivity at which the temperature on the surface of asphalt samples is the highest. Even when particles are well-distributed after mixing, we found that asphalt samples containing larger particles display inhomogeneous heating during the exposure to the AMF. The mechanical recovery of samples during a double torsion test before and after the exposure to the AMF confirmed the healing capability of asphalt materials containing iron-based particles. Based on these results we provide guidelines for the design of magnetically-responsive asphalts for road pavements of enhanced durability.

  • 68. Jeoffroy, E.
    et al.
    Koulialias, D.
    Yoon, S.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Studart, A. R.
    Iron oxide nanoparticles for magnetically-triggered healing of bituminous materials2016Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 112, s. 497-505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Healing of micro-cracks is crucial for recovering the mechanical properties and extending the service time of bituminous materials. However, crack closure is often challenged by the efficiency and repeatability of the healing process or its technical and economic feasibility for large-scale applications. Here, we propose an innovative method to close micro-cracks in bituminous materials by using magnetically-triggered iron oxide nanoparticles as heating agents. Heating is generated through the so-called hyperthermia effect upon exposure of the nanoparticles to an external oscillating magnetic field. When mixed in a low volume fraction of 1% within bitumen, the nanoparticles generate enough heat to decrease the viscosity of the surrounding material and thus promote crack closure. Oleic acid is used to coat the iron oxide nanoparticles and enable their homogeneous distribution in the bitumen. Because of high hysteresis losses, γ-Fe2O3 nanoparticles with a mean crystallite size of 50 nm exhibited specific absorption rates (SAR) as high as 285 W/g when subjected to a magnetic field of 30 mT at 285 kHz. In contrast to the relatively slow heating of electrically-conductive additives, we find that iron oxide nanoparticles pre-embedded in bitumen allows for crack closure in a few seconds when subjected to similar magnetic field conditions. This represents a new efficient way to heal damage in thermoplastic road pavements in the presence of mineral aggregates.

  • 69. Jermer, Jöran
    et al.
    Wong, Andrew H.H.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Nilsson, Thomas
    Durability testing of coconut shell according to ENV 8072011Konferensbidrag (Refereegranskat)
  • 70. Joffre, Thomas
    et al.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Persson, Cecilia
    Bardage, Stig L.
    Hendriks, Cris L. Luengo
    Isaksson, Per
    Characterization of interfacial stress transfer ability in acetylation-treated wood fibre composites using, X-ray microtomography2017Ingår i: INDUSTRIAL CROPS AND PRODUCTS, ISSN 0926-6690, Vol. 95, s. 43-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of the fibre/matrix interface contribute to stiffness, strength and fracture behaviour of fibre-reinforced composites. In cellulosic composites, the limited affinity between the hydrophilic fibres and the hydrophobic thermoplastic matrix remains a challenge, and the reinforcing capability of the fibres is hence not fully utilized. A direct characterisation of the stress transfer ability through pull-out tests on single fibres is extremely cumbersome due to the small dimension of the wood fibres. Here a novel approach is proposed: the length distribution of the fibres sticking out of the matrix at the fracture surface is approximated using X-ray microtomography and is used as an estimate of the adhesion between the fibres and the matrix. When a crack grows in the material, the fibres will either break or be pulled-out of the matrix depending on their adhesion to the matrix: good adhesion between the fibres and the matrix should result in more fibre breakage and less pull-out of the fibres than poor adhesion. The effect of acetylation on the adhesion between the wood fibres and the PLA matrix was evaluated at different moisture contents using the proposed method. By using an acetylation treatment of the fibres it was possible to improve the strength of the composite samples soaked in the water by more than 30%.

  • 71. Johansson, Jimmy
    et al.
    Sandberg, Dick
    Söderström, Ove
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Capillarity in hardwood: An important factor for hardwood market expansion2007Konferensbidrag (Refereegranskat)
  • 72.
    Johansson, Malin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    A study of potential climate impacts from maintenance and replacements in timber buildings: From a lifecycle perspective2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The building sector contributes to a large part of the total emissions of greenhouse gases, which demands for increased sustainability in all phases of a buildings’ lifecycle. Choices of building materials and the respective required maintenance and replacements are becoming more important if further reductions of climate impacts should be obtained.

    Folkhem is a Swedish construction company who constructs multi-storey buildings made of wood. The company has shown interest in developing knowledge about how the selection of building materials effects the impacts on climate, the extent of necessary maintenance and replacement work as well as economic consequences. The aim of this master thesis was to evaluate the potential climate impacts and costs for different scenarios of maintenance and replacements of selected exterior building components for Folkhem’s planned building in Stadshagen, in Stockholm. The façade, roof, windows and balconies have been in focus. To fulfill the aim of this study, life cycle assessment and a simplified cost analysis have been carried out.

    With the basis of the results from this study, recommendations of building materials for the chosen building components in Folkhem’s planned building have been stated. A façade made of pine impregnated with boiled linseed oil is recommended as façade cladding, and OrganoWood is recommended for the balcony decking. Folkhem planned to use wooden windows, but it is recommended that these are substituted to aluminum coated wooden windows. No recommendation could be provided for the roof from this study. The following conclusions have been made;

    • More attention should be payed to the phases of maintenance and replacement when carrying out LCAs for timber buildings, since general assumptions could be misleading.
    • The origin of the building materials could have a significant climate impact if several replacements need to be performed, since this includes a large number of transports of materials.
    • Different building materials or building components have different lifespans and needs for maintenance. To reduce costs and potential climate impacts, long lifespans with little need for maintenance are desired. Planning for a specific lifespan of the building and the required maintenance and replacements may contribute to reduce the potential climate impacts.
    • Maintenance is recommended for timber buildings, since this could reduce the need for replacements, which could reduce the potential climate impacts.
    • LCA can be a useful tool for Folkhem to plan for maintenance and replacements of their timber buildings if improvements are performed regarding LCA data quality.
    • LCA can provide guidance for Folkhem to choose sustainable building materials, with regards to maintenance and replacements at an early stage in the design process.

    A future study could be to perform a more detailed LCA of the materials and products that required assumptions in this study, for instance the surface treatments for maintenance. A more detailed LCA of all maintenance that should be conducted in a building could be of interest as well, and to investigate the impacts from excluded processes in this study. Alternative building materials for the exterior building components could be evaluated as well as different percentages of painting area. More impact categories than climate change could also be evaluated. Impacts from the building lifecycle phases of repair and refurbishment could also be interesting to evaluate in order to receive an overview of the total potential climate impacts and costs from all parts of the lifecycle of a building. Another approach could be to investigate if maintenance and replacement are carried out as described from technical literature and manufacturers in reality. Finally, a more thorough cost analysis could be carried out, evaluating how a housing society would be affected from costs from maintenance and replacement. 

  • 73. Jones, Dennis
    et al.
    Englund, Finn
    Henriksson, Marielle
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Trey, Stacy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ziethen, Rune
    Gonzales, Sergio
    Segui, Luis
    Development of a novel wood based panel for use in internal door manufacture2012Ingår i: Proceedings of the 5th International Conference on Environmentally-Compatible Forest Products, 2012Konferensbidrag (Refereegranskat)
  • 74.
    Karami, Peyman
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsteknik.
    Twumasi, Ebenezer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Gudmundsson, Kjartan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsteknik.
    A comparative study of methods for evaluating the thermal conductivity of nanoporous silica materials for vacuum insulation panelsArtikel i tidskrift (Övrigt vetenskapligt)
  • 75.
    Khavassefat, Parisa
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, Bjorn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    The effect of road surface deterioration on pavement service life2014Ingår i: Expanding horizons: 13th International Symposium on Heavy Vehicle Transport Technology, San Luis, Argentina, 27-31 October 2014, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The effect of pavement surface deterioration on pavement service life has been studied for a set of case studies. The Swedish mechanistic empirical design method is used in order to analyse the pavement performance under dynamic moving loads while the longitudinal profile unevenness is updated on yearly basis. The surface evolution assumed in the case scenarios are chosen in relevance with the general trend of surface deterioration in Swedish road network. Results from the case studies indicate that the pavement service life is highly affected by pavement surface deterioration, especially for pavement segments with high traffic. Moreover predictive maintenance for high traffic road segments might be beneficial as it increases pavement service life and decreases the user related costs, e.g. vehicle fuel consumption.

  • 76.
    Kristjánsdóttir, Rut
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Design of Heavy DutyPavements2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This research is focused on design of Heavy Duty Pavement which is when a pavement loading exceeds highway levels. The environment where these conditions occur are for example at ports, industrial areas and airport because of the use of heavy vehicles as handling of containers by Straddle Carriers, Front Lift Trucks or Reach Stackers, airplanes and more. The main emphasis here will be on heavy duty pavements for ports. Different design methods are discussed and compared for the pavement design of ports. In this research two different design methods are thoroughly analyzed, the British Ports Associations Heavy Duty Pavements Manual which is a chart based procedure and the HIPAVE program which is an Australian Heavy Duty Pavement Design Guide. Both those methods are widely used around the world. Furthermore, an analysis is performed to research the plastic properties of the pavement. In most design methods, the material properties of the granular materials are assumed as elastic when they are not, they are elasto-plastic. A Finite Element Analysis is performed to determine if this assumption has significant effect on the design of pavements by comparing models of a design pavement section with elastic granular materials and elasto-plastic granular materials. The main conclusions from the comparison study of different pavement design methods are when using the HIPAVE program the total thickness of the design pavement section is smaller than using the British Ports Manual. Smaller thickness result in less materials needed for and therefor lower cost for the pavement section. Regarding the plasticity analysis, it is concluded that the assumption to model the behavior of unbound granular materials as elastic in pavement design is correct. The Finite Element Analysis determined that plasticity does have effect on the behavior of the materials with respect to elastic behavior, but there is not a considerable difference in pavement displacement between the two analysis.

  • 77. Kymalainen, M.
    et al.
    Hautamaki, S.
    Lillqvist, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, L.
    Surface modification of solid wood by charring2017Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, nr 10, s. 6111-6119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most wooden structures for outdoor applications require repetitive maintenance operations to protect the surfaces from adverse effects of weathering. One-sided surface modification of boards with a relatively fast charring process has the potential to increase the durability and service life of wooden claddings. To assess some weathering-related effects on surface charred wood, spruce and pine sapwood were subjected to a series of long charring processes (30-120 min) at a moderate temperature of 250 A degrees C and to a short one (30 s) at a high temperature of 400 A degrees C. The wettability and contact angles of treated samples were investigated, and the heat transfer was measured along with the micromorphological changes taking place in the material. The result revealed an increased moisture resistance of charred spruce sapwood and an increased water uptake of pine sapwood. The contact angles of both wood species improved compared to references. Heat conduction measurement revealed that only a thin section of the wood was thermally modified. Some micromorphological changes were recorded, especially on the inside walls of the lumina. The results show that spruce sapwood has an improved resistance towards moisture-induced weathering, but more studies are needed to unlock the potential of surface charred wood.

  • 78.
    Källander, B
    et al.
    SP Technical research Institute of Sweden.
    Wålinder, M. E. P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    European Industry-Academic Cooperation2006Ingår i: Wood Adhesives 2005 / [ed] C. Frihart, Madison: Forest Products Society , 2006, s. 15-22Konferensbidrag (Refereegranskat)
  • 79.
    Källbom, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Characterisation of thermally modified wood for use as component in biobased building materials2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The building sector shows growing interest in biobased building materials. Wood components, here defined as ground or milled wood, i.e. by-products (residuals/residues) from wood processing, such as sawdust or shavings, are valuable raw materials for new types of durable biocomposites suitable for outdoor building applications. An important research question related to such composites is how to characterise and enhance molecular interactions, i.e. adhesion properties, between wood and binder components. Another challenge is the hygroscopicity of the wood component, which can lead to dimensional changes and interfacial cracks during exposure to varying moisture conditions. Thermal modification of wood reduces its hygroscopicity, thereby, increasing its durability, e.g. its dimensional stability and resistance to biodeterioration. The hypothesis is that the use of thermally modified wood (TMW) components in biocomposites can enhance their durability properties and, at the same time, increase the value of residues from TMW processing. The main objective of this thesis is to study and analyse the surface and sorption properties of TMW components using inverse gas chromatography (IGC), dynamic vapour sorption (DVS), X-ray photoelectron spectroscopy (XPS), and the multicycle Wilhelmy plate method. The aim is to gain a better understanding of the surface and sorption characteristics of TMW components to enable the design of optimal adhesion properties and material combinations (compatibility) for use in biocomposites, especially suitable for outdoor and moist building material applications. Samples of TMW and unmodified wood (UW) components of Norway spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) heartwood were prepared and analysed with respect to surface energetics, hygroscopicity, liquid sorption and resulting swelling. The work also included analysis of surface chemical composition, as well as influences of extractives and moisture sorption history. The effect of using TMW components in a wood plastic composite (WPC) exposed to a series of soaking-drying cycles in water was studied with a focus on water sorption, swelling and micromorphological changes. The IGC analyses indicate that TMW components of spruce have a more heterogeneous surface energy character, i.e. a distinctly higher dispersive part of surface energy for low surface coverages, than do UW components. This is suggested to be due to the higher percentage of hydrophobic extractives present in TMW samples. Lewis acid-base analysis indicates that both UW and TMW components from spruce have a predominantly basic character and an enhanced basicity for the latter ones. Results show that both the hygroscopicity and water liquid uptake are lower for TMW than for UW samples. Unexpectedly, a significantly lower rate of water uptake was found for the extracted UW of pine heartwood than for non-extracted samples. In the former case, this is presumably due to contamination effects from water-soluble extractives, which increase capillary flow into wood voids, as proven by a decrease in water surface tension. Water uptake as well as swelling was significantly reduced for the WPCs with TMW and hot-water extracted UW components compared with the WPCs with UW components. This reduction also resulted in fewer wood component-polymer interfacial cracks in the WPCs with the modified wood components.

  • 80.
    Källbom, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Surface characterisation of thermally modified spruce wood and influence of water vapour sorption2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Today there is growing interest within the construction sector to increase the proportion of biobased building materials made from renewable resources. By-products or residuals from wood processing could in this case be valuable resources for manufacturing new types of biocomposites. An important research question related to wood-based biocomposites is how to characterise molecular interactions between the different components in the composite. The hygroscopic character of wood and its water sorption properties are also crucial. Thermal modification (or heat treatment) of wood results in a number of enhanced properties such as reduced hygroscopicity and improved dimensional stability as well as increased resistance to microbiological decay.

    In this thesis, surface characteristics of thermally modified wood components (often called wood fibres or particles) and influencing effects from moisture sorption have been analysed using a number of material characterisation techniques. The aim is to increase the understanding in how to design efficient material combinations for the use of such wood components in biocomposites. The specific objective was to study surface energy characteristics of thermally modified spruce (Picea abies Karst.) under influences of water vapour sorption. An effort was also made to establish a link between surface energy and surface chemical composition. The surface energy of both thermally modified and unmodified wood components were studied at different surface coverages using inverse gas chromatography (IGC), providing information about the heterogeneity of the surface energy. The water vapour sorption behaviour of the wood components was studied using the dynamic vapour sorption (DVS) method, and their surface chemical composition was studied by means of X-ray photoelectron spectroscopy (XPS). Additionally, the morphology of the wood components was studied with scanning electron microscopy (SEM).

    The IGC analysis indicated a more heterogeneous surface energy character of the thermally modified wood compared with the unmodified wood. An increase of the dispersive surface energy due to exposure to an increased relative humidity (RH) from 0% to 75% RH at 30 ˚C was also indicated for the modified samples. The DVS analysis indicated an increase in equilibrium moisture content (EMC) in adsorption due to the exposure to 75% RH. Furthermore, the XPS results indicated a decrease of extractable and a relative increase of non-extractable compounds due to the exposure, valid for both the modified and the unmodified wood. The property changes due to the increased RH condition and also due to the thermal modification are suggested to be related to alterations in the amount of accessible hydroxyl groups in the wood surface. Recommendations for future work and implications of the results could be related to knowledge-based tailoring of new compatible and durable material combinations, for example when using thermally modified wood components in new types of biocomposites for outdoor applications.

  • 81.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Altgen, Michael
    Georg August Univ Gottingen, Wood Biol & Wood Prod, DE-37077 Gottingen, Germany.;Aalto Univ, Dept Bioprod & Biosyst, FI-00076 Aalto, Finland..
    Militz, Holger
    Georg August Univ Gottingen, Wood Biol & Wood Prod, DE-37077 Gottingen, Germany..
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Sorption and surface energy properties of thermally modified spruce wood components2018Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 50, nr 3, s. 346-357Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T = 150 degrees C and RH = 100% (TMW150), and T = 180 degrees C and RH = 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with the UW samples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for the TMW compared with the UW samples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.

  • 82.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Laine, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Sedighi Moghaddam, Maziar
    SP Technical Research Institute of Sweden.
    Rohumaa, Anti
    Aalto University, Department of Forest Products Technology.
    Segerholm, Kristoffer
    SP Technical Research Institute of Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    The influence of log soaking temperature and thermal modification on the properties of birch veneers2016Ingår i: IRG Annual Meeting, IRG Documents , 2016Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.

  • 83.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Lillqvist, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Spoljaric, Steven
    Seppälä, Jukka
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Hughes, Mark
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wood-plastic composites made from thermally modified spruce wood components and effects of exposure to water-soaking-drying cyclesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The over-all aim of this work is to gain more insight on the potential to use thermally modified wood (TMW) components in wood-thermoplastic composites (WPCs), ie a new type of biobased building material, here defined as TMWPCs, assumed to have significantly increased moisture resistance and durability related to conventional WPCs. The specific objective was to prepare lab-scale TMWPCs and WPC controls with unmodified wood (UW), and to expose these samples to a series of severe water-soaking-drying cycles to study the effects on the water sorption behavior and resulting dimensional and micromorphology changes. TMW was prepared by thermal modification of a spruce board in an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210°C (also matched with an UW board as control). TMW and UW components were then prepared by a Wiley mill and thereafter sifted into a smaller (0.20-0.40 mm) and a larger (0.40-0.63 mm) size fraction. A portion of the wood components were also hot-water extracted (HE) with liquid hot-water. Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio) were then prepared by using a Brabender mixer followed by hot-pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on UV-laser ablation combined with scanning electron microscopy (SEM). An effort was also made to study the wood-thermoplastic interfacial behavior in the composites by dynamic mechanical analysis (DMA). The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling for the TMWPCs compared with the controls. Similarly, the WPCs with HE-UW components showed a significant reduction in water absorption and thickness swelling compared with the controls. In contrast, the samples with HE-TMW components resulted in only minor moisture property changes. These observations were also in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. The DMA indicated better dispersion and increased interfacial interaction for the WPCs with UW components with the smaller size fraction compared with the larger size fraction. The loss modulus and storage modulus were overall reduced for samples with HE and TMW components compared with those with UW components. Based on these observations it is suggested that a potential biobased building material with increased durability for applications in harsh outdoor environments may be tailored as a TMWPC with a well-defined and comparably small size fractions of TMW components.

  • 84.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Moghaddam, Maziar Sedighi
    Wålinder, Magnus E. P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction2018Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, nr 3, s. 251-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of extractives removal on liquid sorption, swelling and surface energy properties of unmodified wood (UW) and thermally modified Scots pine heartwood (hW) (TMW) was studied. The extraction was performed by a Soxtec procedure with a series of solvents and the results were observed by the multicycle Wilhelmy plate method, inverse gas chromatography (IGC) and Fourier transform infrared (FTIR) spectroscopy. A significantly lower rate of water uptake was found for the extracted UW, compared with the unextracted one. This is due to a contamination effect in the latter case from water-soluble extractives increasing the capillary flow into the wood voids, proven by the decreased water surface tension. The swelling in water increased after extraction 1.7 and 3 times in the cases of UW and TMW, respectively. The dispersive part of the surface energy was lower for the extracted TMW compared to the other sample groups, indicating an almost complete removal of the extractives. The FTIR spectra of the extracts showed the presence of phenolic compounds but also resin acids and aliphatic compounds.

  • 85.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Ormondroyd, Graham
    Biocomposites Centre, Bangor University, United Kingdom.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden, Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden, Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Surface energy characteristics of refined fibres at different pressures2014Ingår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014) / [ed] Wilson, Peter, 2014, s. 134-138Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Wood fibres were produced on the pilot scale refiner at the BioComposites Centre, Bangor University, from a commercially sourced mix of chipped wood. The fibres were produced at refiner pressure 4, 6, 8 and 10 bar and dried in the associated flash drier. Surface energy characterization of the refined fibres was performed using inverse gas chromatography (IGC). The dispersive part of the total surface energy was analysed for duplicates of fibre samples at the four different refiner pressures. Non-polar alkane probes were used for the dispersive surface energy analysis at different surface coverage. Results indicate that the processing pressure has an effect of the dispersive surface energy and IGC analysis could be developed as a tool both for process development and process control in refining fibres.

  • 86.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Aalto University, Department of Forest Products Technology.
    Johansson, Leena-Sisko
    Aalto University, Department of Forest Products Technology.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Laine, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Aalto University, Department of Forest Products Technology.
    Surface chemical analysis and water vapour sorpion of thermally modified wood exposed to increased relative humidity2015Ingår i: The Eighth European Conference on Wood Modification (ECWM8) 2015 / [ed] Mark Hughes, Lauri Rautkari, Tuuli Uimonen, Holger Militz and Brigitte Junge, 2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The increased interest in environmentally friendly building materials is accompanied with an increased need for research on thermally modified wood. Products made from recycling or reusing of thermally modified residuals will have advantages in terms of environmental aspects. Surface characteristics of thermally modified wood play an important role for the development of applications involving bonding processes, for example when using thermally modified wood residuals in biocomposites. Surface chemistry characteristics are important in developing such materials. A technique used for surface chemical analysis of the outermost surface is X‑ray photoelectron spectroscopy (XPS). Some surface chemical analyses of wood and modified wood can be found in Nzokou and Kamdem (2005), Inari et al. (2006), Bryne et al. (2010), Johansson et al. (2012), Rautkari et al. (2012). Furthermore, the influence of water and moisture has crucial effect on the properties of wood and wood products. Water vapour sorption properties of hygroscopic materials can be studied using a dynamic vapour sorption (DVS) instrument. Previous studies on thermally modified wood exposed to several sorption cycles using DVS have shown an increase in hysteresis during the first cycle, compared with unmodified wood (Hill et al., 2012). However, during the second and the third sorption cycle a reduction in sorption hysteresis was observed.

     

    The objective of this work was to study the surface chemical composition and water vapour sorption properties of thermally modified wood. In particular, an effort was made to study any influence on such properties due to a previous exposure to a high relative humidity (RH). Interpretations of the results indicate a decrease of extractable or volatile organic components and a relative increase of non-extractable components, for the high humidity-exposed samples. This could be due to remaining extractives migrating towards or redistribution at the wood surface layer as a result of moisture diffusion. The DVS results show that the thermally modified wood samples that had been exposed to the high relative humidity condition revealed a slight decrease of the hysteresis of the sorption isotherms. The opposite trend was furthermore seen for the unmodified wood.

  • 87.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Johansson, Leena-Sisko
    Aalto University, Finland.
    Campbell, JM
    Department of Forest Products Technology, Aalto University.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden, Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Laine, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Water vapour sorption characteristics and surface chemical composition of thermally modified spruce (Picea abies karst)2016Ingår i: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 7, nr 3, s. 116-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this work was to study the hygroscopicity and surface chemical composition of thermally modified (TM) spruce. An effort was also made to study if those features were influenced by a previous exposure to a significant increase in relative humidity (RH). TM and unmodified Norway spruce (Picea abies Karst) samples, both in solid and ground form, were prepared. Water vapour sorption characteristics of the ground samples were obtained by measuring sorption isotherms using a dynamic vapour sorption (DVS). The surface chemical composition of the solid samples, both acetone extracted and non-extracted, were analysed using X-ray photoelectron spectroscopy (XPS). The DVS analysis indicated that the TM wood exposed to the 75% RH revealed a decrease in isotherm hysteresis. The XPS analysis indicated a decrease of acetone extractable or volatile organic components and a relative increase of non-extractable components for the samples exposed to the increased RH condition.

  • 88.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Johansson, Leena-Sisko
    Department of Forest Products Technology, Aalto University.
    Campbell, Joseph
    Department of Forest Products Technology, Aalto University.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Water vapour sorption characteristics and surface chemical composition of thermally modified spruceManuskript (preprint) (Övrigt vetenskapligt)
  • 89.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Wood Material Science and Technology, Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden.
    Water vapour sorption properties and surface chemical analysis of thermally modified wood particles2014Ingår i: Recent Advances in the field of TH and THM Wood Treatment, 2014Konferensbidrag (Övrigt vetenskapligt)
  • 90.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, Dennis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Surface energy characterization at different moisture levels of thermally modified wood using inverse gas chromatography2013Ingår i: Proceedings of the 9th meeting of the Northern European Network for Wood Science and Engineering (WSE) / [ed] Briscke, C. & Meyer, L., 2013, s. 130-135Konferensbidrag (Övrigt vetenskapligt)
  • 91.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Surface energy characterization of thermally modified wood particles exposed to humidity cycling using inverse gas chromatography2014Ingår i: / [ed] Nunes, L., Jones, D., Hill, C. and Militz, H., 2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The objective of this work was to study surface energetics of thermally modified wood particles exposed to dry-humid cycling. This information can give insight in the adhesion properties between the modified wood and composite matrices, adhesives or coatings. The surface energy characterization as well as the dry-humid cycling was performed using inverse gas chromatography (IGC). Duplicates of thermally modified and unmodified spruce particles with size 0-0.125 mm were investigated and conditioned in dry-humid cycles at 0-75 % RH and 0‑25 % RH. The BET specific surface area as well as the dispersive surface energy heterogeneity (or distribution) at different surface coverage was determined. The results showed similar trends for the different cycles in the dry and humid states, respectively. The difference in dispersive surface energy distribution between the dry and humid state was more pronounced at the lower surface coverage.

  • 92.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, Dennis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Surface energy characterization of thermally modified wood using inverse gas chromatography2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The objective of this work is to characterize surface energetics of thermally modified wood. Such information may be useful for a better understanding and predictions of adhesion properties between the modified wood and other material systems, e.g. coatings, adhesives or matrices in composites. Inverse gas chromatography (IGC) was used to study the surface energy characteristics of thermally modified spruce in particle form. Two different wood component samples were prepared, one with a larger and one with a smaller particle size distribution. Measurements of BET specific surface area and dispersive surface energy distribution of the particle samples are presented. Results indicate that a ground wood component of a finer size distribution of thermally modified wood is less energetically heterogeneous compared with a component with a larger size distribution.

  • 93.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, Dennis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Physico-chemical characterization of THM modified wood using inverse gas chromatography (IGC)2013Ingår i: Evaluation, processing and prediction of THM treated wood behaviour by experimental and numerical methods, 2013, s. 35-36Konferensbidrag (Övrigt vetenskapligt)
  • 94.
    Källbom, Susanna
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions2015Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 47, nr 4, s. 410-420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m(2) corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample are related to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.

  • 95.
    Källman, Malin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Korrosion hos fästdon i brandsskyddat trä2009Självständigt arbete på grundnivå (yrkesexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
  • 96.
    Laine, Kristiina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Tech Res Inst Sweden, Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, L.
    Hughes, M.
    Lankveld, C.
    Surface densification of acetylated wood2016Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, nr 6, s. 829-835Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical properties of wood can be improved by compressing its porous structure between heated metal plates. By adjusting the process parameters it is possible to target the densification only in the surface region of wood where the property improvements are mostly needed in applications, such as flooring. The compressed form is, however, sensitive to moisture and will recover to some extent in high humidity. In this study, therefore, acetylated radiata pine was utilised in the surface densification process in order to both reduce the set-recovery of densified wood and to improve the hardness of the acetylated wood. Pre-acetylation was found to significantly reduce the set-recovery of surface densified wood. However, after the second cycle the increase in set-recovery of acetylated wood was relatively higher than the un-acetylated wood. The acetylated samples were compressed by only 1 mm (instead of the target 2 mm), yet, the hardness and hardness recovery of the acetylated samples significantly increased as a result of densification. It was also discovered that rough (un-planed) surfaces may be surface densified, however, even if the surface became smooth to the touch, the appearance remained uneven.

  • 97.
    Laine, Kristiina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Hughes, Mark
    Wood densification and thermal modification: hardness, set-recovery and micromorphology2016Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 5, s. 883-894Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation in water-soaking. This phenomenon, termed set-recovery, was reduced by thermally modifying the wood after densification. This study presents the influence of compression ratio (CR = 40, 50, 60 %) and thermal modification time (TM = 2, 4, 6 h) on the hardness and set-recovery of densified wood. Previously, set-recovery has mainly been studied separately from other properties of densified wood, while in this work, set-recovery was also studied in relation to hardness. The results show that set-recovery was almost eliminated with TM 6 h in the case of CR 40 and 50 %. Hardness significantly increased due to densification and even doubled compared to non-densified samples with a CR of 50 %. Set-recovery reduced the hardness of densified (non-TM) wood back to the original level. TM maintained the hardness of densified wood at an increased level after set-recovery. However, some reduction in hardness was recorded even if set-recovery was almost eliminated.

  • 98.
    Laine, Kristiina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Källbom, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, Dennis
    SP Tech Res Inst Sweden.
    Hardness, set-recovery and micromorphology studies of densified and thermally modified wood2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The purpose of the work reported in this paper was to increase the density of Scots pine wood in order to improve its hardness. Density was increased by compressing the porous structure of wood between heated metal plates in the radial direction by 40, 50 or 60% of the thickness. The compressed state was stabilised by thermally modifying (TM) the samples at 200 °C under steam conditions for 2, 4 or 6h. Set-recovery was almost eliminated (<1%) with TM of 6h for samples compressed 40 and 50%. It was discovered that hardness of densified wood was in some cases even three times higher compared to untreated wood. However, the hardness of the densified, non-TM wood was reduced after soaking and drying back to the original untreated level, while TM of 4 and 6h maintained an increased level of hardness.

  • 99.
    Laine, Kristiina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Rowell, Roger
    Department of Biological Systems Engineering, University of Wisconsin, Madison, WI USA.
    Acetylation and densification of wood2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The purpose of this study was to explore the possibility to surface densify acetylated solid wood. The aim of surface densification is to improve mechanical properties, such as hardness, at the very surface of wood where the property improvements are mostly needed (e.g. in flooring and decking). However, when subjected to moisture, surface densified wood may swell back almost to the original dimensions. Therefore, acetylated and non-acetylated wood was surface densified in order to investigate whether the dimensional stability of densified wood may be improved by pre-acetylation. Surface densification was performed by compressing the acetylated radiate pine samples between metal plates with only one side heated (150°C) in order to target the deformation to one surface only. The original thickness of the samples was 20 mm and the target thickness 18 mm which was controlled by metal stops. The recovery of the deformation (set-recovery) was measured by soaking the samples in water and measuring the oven-dry thickness before and after soaking in repeated cycles. It was found that acetylated wood may be surface densified and indeed the set-recovery of the pre-acetylated wood was significantly lower (17.4 %) compared to non-acetylated wood (72.8 %). Further studies in adjusting the process parameters might lead to even higher reduction in set-recovery.

  • 100. Laine, Kristiina
    et al.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Ormondroyd, Graham
    Hughes, Mark
    Jones, Dennis
    Micromorphological studies of surface densified wood2014Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, nr 5, s. 2027-2034Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) wood was surface densified in its radial direction in an open press with one heated plate to obtain a higher density on the wood surface whilst retaining the overall thickness of the sample. This study investigated the effect of temperature (100, 150 and 200 A degrees C) and press closing speed (5, 10 and 30 mm/min, giving closing times of 60, 30 and 10 s, respectively) on the micromorphology of the cell-wall, as well as changes occurring during set-recovery of the densified wood. The micromorphology was analysed using scanning electron microscopy (SEM) combined with a sample preparation technique based on ultraviolet-excimer laser ablation. Furthermore, the density profiles of the samples were measured. Low press temperature (100 A degrees C) and short closing time (10 s) resulted in more deformation through the whole thickness, whilst increasing the temperature (150 and 200 A degrees C) and prolonging the closing time (30 and 60 s) enabled more targeted deformation closer to the heated plate. The deformation occurred in the earlywood regions as curling and twisting of the radial cell-walls, however, no apparent cell-wall disruption or internal fracture was observed, even at low temperatures and fast press closing speed, nor after soaking and drying of the samples. In the SEM-analysis after soaking and drying, it was noticed that the cells did not completely recover their original form. Thus, part of the deformation was considered permanent perhaps due to viscoelastic flow and plastic deformation of the cell-wall components.

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