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  • 1.
    Berktas, Ilayda
    et al.
    Sabanci University, Turkey.
    Ghafar, Ali
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Fontana, Patrick
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Caputcu, Ayten
    Cimsa Cimento Sanayi AS, Turkey.
    Menceloglu, Yusuf
    Sabanci University, Turkey.
    Okan, Burcu
    Sabanci University, Turkey.
    Facile synthesis of graphene from waste tire/silica hybrid additives and optimization study for the fabrication of thermally enhanced cement grouts2020In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 25, no 4, article id 886Article in journal (Refereed)
    Abstract [en]

    This work evaluates the effects of newly designed graphene/silica hybrid additives on the properties of cementitious grout. In the hybrid structure, graphene nanoplatelet (GNP) obtained from waste tire was used to improve the thermal conductivity and reduce the cost and environmental impacts by using recyclable sources. Additionally, functionalized silica nanoparticles were utilized to enhance the dispersion and solubility of carbon material and thus the hydrolyzable groups of silane coupling agent were attached to the silica surface. Then, the hybridization of GNP and functionalized silica was conducted to make proper bridges and develop hybrid structures by tailoring carbon/silica ratios. Afterwards, special grout formulations were studied by incorporating these hybrid additives at different loadings. As the amount of hybrid additive incorporated into grout suspension increased from 3 to 5 wt%, water uptake increased from 660 to 725 g resulting in the reduction of thermal conductivity by 20.6%. On the other hand, as the concentration of GNP in hybrid structure increased, water demand was reduced, and thus the enhancement in thermal conductivity was improved by approximately 29% at the same loading ratios of hybrids in the prepared grout mixes. Therefore, these developed hybrid additives showed noticeable potential as a thermal enhancement material in cement-based grouts. © 2020 by the authors.

  • 2.
    Hingorani, Ramon
    et al.
    Institute for Construction Science Eduardo Torroja, Spain.
    Tanner, Peter
    Institute for Construction Science Eduardo Torroja, Spain.
    Prieto Rábade, Miguel
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Lara, Carlos
    Institute for Construction Science Eduardo Torroja, Spain.
    Consequence classes and associated models for predicting loss of life in collapse of building structures2020In: Structural Safety, ISSN 0167-4730, E-ISSN 1879-3355, Vol. 85, article id 101910Article in journal (Refereed)
    Abstract [en]

    Most building design codes distinguish structural reliability levels in terms of failure consequences, for which they normally define consequence classes based on building type and use. Although readily applicable in everyday practice, that approach may entail adopting inconsistent safety requirements. Such a significant drawback could be minimised by establishing separate reliability levels for key members on the grounds of the potential consequences of their collapse. Further to those concerns, this paper proposes a series of consequence classes determined in keeping with the number of persons at risk in a given collapse scenario and the extent of the respective damage. Consequence class-related models for predicting loss of life are derived from statistical assessments of data on over 150 collapsed buildings. The models developed estimate the number of fatalities and conditional probability of death of building users under given collapse circumstances. In addition to their utility in establishing target reliability values, these models can be applied in risk analysis of specific building structures, especially where the potential consequences of failure are high. 

  • 3.
    Kosmela, Paulina
    et al.
    Gdansk University of Technology, Poland.
    Hejna, Aleksander
    Gdansk University of Technology, Poland.
    Suchorzewski, Jan
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology. Gdansk University of Technology, Poland.
    Piszczyk, Łukasz
    Gdansk University of Technology, Poland.
    Haponiuk, Józef Tadeusz
    Gdansk University of Technology, Poland.
    Study on the Structure-Property Dependences of Rigid PUR-PIR Foams Obtained from Marine Biomass-Based Biopolyol.2020In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 13, no 5, article id E1257Article in journal (Refereed)
    Abstract [en]

    The paper describes the preparation and characterization of rigid polyurethane-polyisocyanurate (PUR-PIR) foams obtained with biopolyol synthesized in the process of liquefaction of biomass from the Baltic Sea. The obtained foams differed in the content of biopolyol in polyol mixture (0-30 wt%) and the isocyanate index (IISO = 200, 250, and 300). The prepared foams were characterized in terms of processing parameters (processing times, synthesis temperature), physical (sol fraction content, apparent density) and chemical structure (Fourier transform infrared spectroscopy), microstructure (computer microtomography), as well as mechanical (compressive strength, dynamic mechanical analysis), and thermal properties (thermogravimetric analysis, thermal conductivity coefficient). The influence of biopolyol and IISO content on the above properties was determined. The addition of up to 30 wt% of biopolyol increased the reactivity of the polyol mixture, and the obtained foams showed enhanced mechanical, thermal, and insulating properties compared to foams prepared solely with petrochemical polyol. The addition of up to 30 wt% of biopolyol did not significantly affect the chemical structure and average cell size. With the increase in IISO, a slight decrease in processing times and mechanical properties was observed. As expected, foams with higher IISO exhibited a higher relative concentration of polyisocyanurate groups in their chemical structure, which was confirmed using principal component analysis (PCA).

  • 4.
    Sadagopan, Madumita
    et al.
    University of Borås, Sweden.
    Malaga, Katarina
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology. University of Borås, Sweden.
    Nagy, Agnes
    University of Borås, Sweden.
    Modified pycnometer method to measure the water absorption of crushed concrete aggregates2020In: Journal of Sustainable Cement-Based Materials, ISSN 2165-0373, E-ISSN 2165-0381Article in journal (Refereed)
    Abstract [en]

    The water absorption of crushed concrete aggregates (CCA) has a major influence on concrete workability. In order to determine the water absorption of CCA, a more porous material than natural aggregates, modifications to the standard pycnometer method are proposed as: (1) Water absorption is measured on a combined fraction CCA consisting of fine and coarse aggregates proportioned according to concrete recipe. (2) The CCA is pre-processed to mitigate sedimentation. (3) Saturated surface dry condition of aggregate is assessed by vacuum filtration and ocular technique. Water absorption development is measured at 0 min, 15 min, and 24 h. About 90% of the 24-h water absorption occurs in 15 min, value which is introduced in the concrete recipe; slump flow and compressive strength are determined. The modified pycnometer method shortens test duration, is operator insensitive and gives reliable water absorption result for CCA leading to concrete workability fitting industrial application. © 2020, © 2020 The Author(s).

  • 5.
    Vega, Alberto
    et al.
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Yarahmadi, Nazdaneh
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Jakubowicz, Ignacy
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Determining the useful life of district heating pipes: Correlation between natural and accelerated ageing2020In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 175, article id 109117Article in journal (Refereed)
    Abstract [en]

    District heating (DH) systems constitute a smart and environmentally friendly solution for energy distribution in the heat sector in Europe. This technique is still expanding but already faces some issues such as status assessment of the current DH networks and the development of new generation networks for low-temperature DH. Therefore, it is essential to understand the ageing behaviour of pipes under operating conditions and to find the relevant parameters that control the degradation processes. Many factors affect the deterioration of DH pipes, especially the polyurethane foam, which makes it very complex to find a reliable prediction model. Models based on a linear Arrhenius relationship using results from high ageing temperatures seem to be incorrect. For this study, 10 pipes that have been in service for many years in Sweden and Norway were evaluated. The aim was to study the impact of natural ageing on the mechanical adhesion and chemical structure of the polyurethane foam, which affects the pipe's performance. A test method developed at the Research Institutes of Sweden (RISE), called RISE plug method, was used to study the mechanical adhesion strength. In addition, Fourier transform infrared spectroscopy was used to observe any change in the chemical structure. The results were compared with previous analyses of DH pipes exposed to accelerated ageing. This information helps to provide a better comprehension of the deterioration of the current generation of pre-insulated DH pipes and to improve the accelerated ageing methods used nowadays to predict the technical lifetime of DH pipes. Our results suggest that the lifetime of DH pipes has been underestimated when using artificial ageing at relatively high temperatures. The data collected from naturally aged pipes gave confirmatory information about their physical status compared with our laboratory tests. This study also suggests that infrared analyses could be used as an early indication of the degradation of the polyurethane foam at the interface with a steel pipe. 

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