Change search
Refine search result
1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Addassi, Mouadh
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wadsö, Lars
    Lund University.
    Inverse analyses of effective diffusion parameters relevant for a two-phase moisture model of cementitious materials2018In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 106, p. 117-129Article in journal (Refereed)
    Abstract [en]

    Here we present an inverse analyses approach to determining the two-phase moisture transport properties re-levant to concrete durability modeling. The purposed moisture transport model was based on a continuumapproach with two truly separate equations for the liquid and gas phase being connected by the sorption ki-netics. The moisture properties of ten binder-systems containingfly ash, calcined clay, burnt shale and graymicro-filler, were investigated experimentally. The experiments used were, (i) sorption test (moisturefixation),(ii) cup test in two different relative humidity intervals, (iii) drying test, and, (iv) capillary suction test. Masschange over time, as obtained from the drying test, the two different cup test intervals and the capillary suctiontest, was used to obtain the effective diffusion parameters using the proposed inverse analyses approach. Themoisture properties obtained with the proposed inverse analyses method provide a good description of the testperiod for the ten different binder-systems.

  • 2.
    Adolfsson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Robinson, Ryan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Björkman, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of mineralogy on the hydraulic properties of ladle slag2011In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 41, no 8, p. 865-871Article in journal (Refereed)
    Abstract [en]

    The present study is aimed at investigating the hydraulic characteristics of ladle furnace slag (LFS), under the pretence of using LFS as a cement substitute in certain applications. Furthermore, LFS has been considered as a possible activator in a blend containing 50% LFS, and 50% ground granulated blast furnace slag (GGBFS). Phases detected in LFS were quantified using Rietveld analysis. Calorimetric studies were performed at 20, 25 and 30 °C in order to calculate the apparent activation energy of hydration and thereby to suggest a kinetic model for the tested compositions within this temperature interval. In addition, compressive strength tests were performed on mortar prisms made with LFS, and LFS/GGBFS which had hydrated for 2, 7 and 28 days. Both compositions reached acceptable early strengths, (e.g. LFS, 33.1 MPa, and LFS/GGBFS, 17.9 MPa, after 2 days), but after 28 days hydration the blend was superior to neat LFS. Related apparent activation energies were determined using an Avrami–Erofeev model and gave Ea = 58 kJ/mol for neat LFS and Ea = 63 kJ/mol for the blend. The results imply that LFS or a LFS/GGBFS blend can be favourably used as supplement in binder applications such as binder in by-product metallurgical briquettes, which are used as recycle to the blast furnace or basic oxygen furnace depending on the specific briquette composition.

  • 3.
    Cwirzen, A.
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Penttala, V.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Vornanen, C.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Reactive powder based concretes: Mechanical properties, durability and hybrid use with OPC2008In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 38, no 10, p. 1217-1226Article in journal (Refereed)
    Abstract [en]

    The basic mechanical properties, frost durability and the bond strength with normal strength concretes of the ultra high strength (UHS) mortars and concretes were studied. The produced mixes had plastic or fluid-like consistency. The 28-day compressive strength varied between 170 and 202 MPa for the heat-treated specimens and between 130 and 150 MPa for the non-heat-treated specimens. The shrinkage values were two times higher for the UHS mortars in comparison with the UHS concretes. After the initial shrinkage, swelling was noticed in the UHS mortars. The lowest creep values were measured for the non-heat-treated UHS concretes. The frost-deicing salts durability of the UHS mortars and concretes appeared to be very good even despite the increased water uptake of the UHS concretes. The study of the hybrid concrete beams indicated the formation of low strength transition zone between the UHS mortar and normal strength concrete. © 2008 Elsevier Ltd. All rights reserved.

  • 4.
    Cwirzen, Andrzej
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Penttala, Vesa
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes2005In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 35, no 4, p. 671-679Article in journal (Refereed)
    Abstract [en]

    The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ. © 2004 Elsevier Ltd. All rights reserved.

  • 5. Damineli, B. L.
    et al.
    John, V. M.
    Lagerblad, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Pileggi, R. G.
    Viscosity prediction of cement-filler suspensions using interference model: A route for binder efficiency enhancement2016In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 84, p. 8-19Article in journal (Refereed)
    Abstract [en]

    Producing cementitious materials with low CO2 emissions is a key challenge for sustainability, considering the increasing demand for cement and the inefficacy of current industrial solutions. Improving the efficiency of binder use is mandatory, so that binder replacement by inert fillers with lower environmental loads is an alternative, which demands careful control of the rheological behaviour to decrease the water demand of pastes. Dispersion and packing models are well known, but other less explored parameters of raw materials (surface area, density, roughness) and paste (water content, distance between particles) determine the interaction among particles, affecting the paste's rheological behaviour. The aim of this paper is to assess the influence of inert fillers on the rheological behaviour of cementitious pastes. A range of 12 inert fillers with varied aspects was evaluated. The results indicated a good agreement between the Casson viscosity and the interference parameter calculated using the interference model.

  • 6.
    Eriksson, Magnus
    et al.
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Friedrich, M
    Vorschulze, C
    Variations in the rheology and penetrability of cement-based grouts: an experimental study2004In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 34, no 7, p. 1111-1119Article in journal (Refereed)
    Abstract [en]

    To ascertain the most suitable grouting mixture to use in a specific project or to facilitate making predictions about grouting outcomes, laboratory tests are usually carried out to determine the properties of the particular grout. This paper presents a number of measurements of grout properties relating to the rheology and penetrability of fresh cement-based grout. The main purpose of this study is to investigate and describe variations that can be detected when measurements of these grout parameters are carried out repeatedly. Furthermore, a number of additional factors that can also influence these grout properties have been identified and examined. This study has shown that grout properties do vary and should therefore not to be regarded as uniform. The rheology-related properties of grout have been found to vary more than the penetrability-related parameters. Furthermore, it was found that the water-cement (w/c) ratio, the cement condition, and the mixing equipment could significantly influence the grout properties investigated in this study. Based on these experimental findings, it is therefore recommended that repeated testing be carried out on a specific grout mixture in preference to relying on the results of a single test.

  • 7.
    Gasch, Tobias
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Eriksson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    On the behaviour of con-crete at early-ages: A multiphase description of hygro-thermo-chemo-mechanical properties2019In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 116, p. 202-216Article in journal (Refereed)
    Abstract [en]

    Understanding the early-age behaviour of concrete is of importance for designing durable concrete structures. To contribute to the improvement of this, a hygro-thermo-chemo-mechanical model is presented that accounts for phenomena such as hydration, external and internal drying, self-heating, creep, shrinkage and fracture. The model is based on a multiphase porous media framework, using the Thermodynamically Constrained Averaging Theory (TCAT) as starting point to derive the governing equations of the system. This allows for a systematic treatment of the multiscale properties of concrete and how these develop during hydration, e.g. chemical and physical fixation of water. The proposed mathematical model is implemented within the context of the Finite Element Method (FEM), where all physical fields are solved in a fully-coupled manner. Chosen properties of the model are demonstrated and validated using three experimental results from the literature. Generally, the simulated results are in good agreement with the measurements.

  • 8.
    Gram, Annika
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    McCarthy, R.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Linking Numerical Simulation of Fresh Concrete Flow to On-Site Casting2009In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948Article in journal (Refereed)
  • 9.
    Gram, Annika
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Silfwerbrand, Johan
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Obtaining rheological parameters from flow test: analytical, computational and lab test approach2014In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 63, p. 29-34Article in journal (Refereed)
    Abstract [en]

    In the mix design process of cementitious suspensions, an adequate rheology of the cement paste is crucial. A novel rheological field test device for cementitious fluids is presented here and investigated theoretically, by computer simulation and by lab tests. A simple flow stoppage test with a timed spread passage point provides accurate rheological parameters according to the Bingham material model. Values for yield stress and plastic viscosity are obtained for a test specimen of no more than 19.75 · 10- 6 m3 of fluid. This volume is equivalent to 19.75 g of water at room temperature. Such a small volume allows reliable tests even for small amounts of fillers. Promising results show that both yield stress and plastic viscosity can be determined by this simple test. This novel rheological test method also enables the correlation of different rheological equipment used by different laboratories.

  • 10.
    Gram, Annika
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Swedish Cement and Concrete Research Institute (CBI), Sweden.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Swedish Cement and Concrete Research Institute (CBI), Sweden.
    Lagerblad, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Swedish Cement and Concrete Research Institute (CBI), Sweden.
    Obtaining rheological parameters from flow test - Analytical, computational and lab test approach2014In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 63, p. 29-34Article in journal (Refereed)
    Abstract [en]

    In the mix design process of cementitious suspensions, an adequate rheology of the cement paste is crucial. A novel rheological field test device for cementitious fluids is presented here and investigated theoretically, by computer simulation and by lab tests. A simple flow stoppage test with a timed spread passage point provides accurate rheological parameters according to the Bingham material model. Values for yield stress and plastic viscosity are obtained for a test specimen of no more than 19.75 . 10(-6) m(3) of fluid. This volume is equivalent to 19.75 g of water at room temperature. Such a small volume allows reliable tests even for small amounts of fillers. Promising results show that both yield stress and plastic viscosity can be determined by this simple test. This novel rheological test method also enables the correlation of different rheological equipment used by different laboratories.

  • 11.
    Johannesson, Björn
    Lund Institute of Technology.
    A theoretical model describing diffusion of a mixture of different types of ions in pore solution of concrete coupled to moisture transport2003In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 33, no 4, p. 481-488Article in journal (Refereed)
    Abstract [en]

    A theoretical model is established for diffusion of different types of ions in pore solution of concrete and the coupling to moisture flow and moisture content. Mass exchanges between ions in pore solution and solid hydration products in the concrete are also considered. The basic concepts behind the so-called mixture theory are used. The development of a mass balance principle for ions in pore solution is established. This principle accounts for (i) diffusion caused by concentration gradients of ions and gradients of the so-called internal electrical potential, (ii) convection, i.e. the effect on the motion of ions due to a motion of the pore solution in concrete, (iii) the effect on the concentration due to changes in the moisture content, and finally, (iv) the effect of mass exchange of ions between solid hydration products and the bore solution phase. The model is general in the sense that all different types of ions appearing in pore solution phase can-be included and computed for during quite arbitrary boundary conditions.

  • 12.
    Johannesson, Björn
    Lund Institute of Technology.
    Diffusion of a mixture of cations and anions dissolved in water1999In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 29, no 8, p. 1261-1270Article in journal (Refereed)
    Abstract [en]

    In service life modeling of concrete, the ion transport in the pore solution is crucial. The main deterioration phenomena associated with ions in the pore solution are (1) corrosion due to external chloride ions reaching the embedded reinforcement bars; (2) carbonation due to presence of dissolved carbon dioxide (which will form carbonic acid with water) supplied from the surrounding air. and (3) leaching of hydroxide ions from the pore solution to the surrounding environment. Models dealing with diffusion of ions are usually based on the mass balance equations for the individual diffusing ions together with constitutive relations for the mass density flows and for the mass exchange among the constituents. The important consequences of electroneutrality among the diffusing ions, however, is often omitted in models dealing with diffusion of ions in the pore solution of concrete. Here a method will be examined that allows diffusion of different ions in water, which satisfies both the electroneutrality requirement and the mass balance laws. For simplicity the effect of built-up electric double layers on the charged pore walls will not be treated.

  • 13.
    Johannesson, Björn
    Lund Institute of Technology.
    Prestudy on diffusion and transient condensation of water vapor in cement mortar2002In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 32, no 6, p. 955-962Article in journal (Refereed)
    Abstract [en]

    The kinetics of sorption of water vapor in mature cement mortar are examined experimentally by the use of a sorption balance (DVS1000). The relative humidity in the sample chamber is obtained by mixing dry and saturated air using flow regulators with very high accuracy. A predefined change of relative humidity in the sample chamber can be obtained in about 30 s. The time needed for equilibration in terms of the mass of a finely grained mortar sample is shown to be in the order of 2500 min for a 0-96% step in relative humidity at 25 degreesC. This fact calls for a refinement of modeling of diffusion of water vapor in materials such as mortar to take into account the kinetics of sorption. The established model involves a transient mass exchange term that explicitly describes the rate of condensation at internal material surfaces. This function becomes zero when located at the equilibrium sorption isotherm. The 'global' mass diffusion velocity of water vapor in the air-filled porosity is assumed to be significantly affected by the mass concentration of liquid water in the pore space. A satisfying match between the proposed model and measurements presented by U. Daian [Transp. Porous Media 4 (1989) 1.] was obtained by using nonlinear diffusion and sorption characteristics. In order to get a satisfying match, the sorption kinetics was, however, forced to be much slower than the recorded values obtained by the sorption balance. Some speculations as to the reason of this marked difference are performed. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 14.
    Johannesson, Björn
    et al.
    Lund Institute of Technology.
    Utgenannt, Peter
    Lund Institute of Technology.
    Microstructural changes caused by carbonation of cement mortar2001In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 31, no 6, p. 925-931Article in journal (Refereed)
    Abstract [en]

    The change of specific surface area and pore size distribution due to carbonation of an ordinary Portland cement mortar is investigated. The adsorption of water vapor on noncarbonated and well-carbonated cement mortar is measured in order to evaluate the difference in specific surface area for the two samples using the BET theory. From the measured desorption the pore size distribution is calculated using the Kelvin formula. A sorption balance is used to measure the sorption characteristics for the two studied sample qualities. In this method dry and saturated air are mixed in desired proportion in a closed system. One of the benefits of the method is that the samples not are exposed to carbon dioxide during testing, i.e., undesired effects caused by carbonation on the sorption can be eliminated. The specific surface area for a noncarbonated sample was calculated, using the measured adsorption data, to be 8% higher than for the well-carbonated sample. The difference in pore size distributions was more marked than the difference in specific surface area for the two samples. The well-carbonated mortar had about twice as much volume attributed to small pores as the noncarbonated cement mortar.

  • 15. Johansson, Karin
    et al.
    Larsson, C.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Ronin, Vladimir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Reply to the discussion by Knut O. Kjellsen of the paper "Kinetics of the hydration reactions in the cement paste with mechanochemically modified cement: 29Si magic-angle-spinning NMR study"2000In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 30, no 8, p. 1325-1328Article in journal (Refereed)
  • 16.
    Johansson, Karin
    et al.
    Luleå tekniska universitet.
    Larsson, Cecilia
    Luleå tekniska universitet.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ronin, Vladimir
    Kinetics of the hydration reactions in the cement paste with mechanochemically modified cement 29Si magic-angle-spinning NMR study1999In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 29, no 10, p. 1575-1581Article in journal (Refereed)
    Abstract [en]

    A comparative 29Si solid state NMR study of kinetics of the hydration reactions in cement pastes based on rapid-hardening ordinary Portland cement (SH) and on the mechanochemically modified cement (MSH) is presented. The mechanical activation of a cement/silica fume blend in a vibrating mill accelerates the hydration reactions by 15-20%, especially during the initial period of hardening. Variations in relative intensities of 29Si resonances assigned to the hydration products in SH/MSH blends suggest different structures of hydrated SH nets. This can be correlated with a pronounced increase of the MSH-cement binding capacity reported earlier.

  • 17.
    Justnes, Harald
    et al.
    SINTEF Civil & Environmental Engineering, Trondheim.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ronin, Vladimir
    Mechanism for performance of energetically modified cement versus corresponding blended cement2005In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 35, no 2, p. 315-323Article in journal (Refereed)
    Abstract [en]

    The microstructure of cement paste of 50/50 mixes of cement/quartz and cement/fly ash, both ground in a special mill [energetically modified cement (EMC) process] and simply blended, have been studied under sealed curing conditions. The grinding process reduced the size of both cement grains and quartz/fly ash markedly and created flaky agglomerates of high inner surface for the finer particles. EMCs had much higher degree of hydration at 1 day, but similar as blends at 28 days. The pores were much finer for EMC paste due to smaller particles as also reflected in the strength. The morphology of calcium hydroxide in EMC paste appeared more mass like. Pozzolanic reaction was insignificant for quartz in EMC, but increased for fly ash. Thus, improved performance of EMC versus OPC can be explained by increased early hydration and extensive pore size refinement of the hardened binder resulting in reduced permeability and diffusivity for concrete.

  • 18.
    Kauppi, A
    et al.
    YKI – Ytkemiska institutet.
    Andersson, KM
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    Probing the effect of superplasticizer adsorption on the surface forces using the colloidal probe AFM technique2005In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 35, p. 133-140Article in journal (Refereed)
    Abstract [en]

    The interactions between adsorbed superplasticizer layers have been studied using direct force measurements, with an atomic force microscope. MgO was used as a nonreactive model system for cement, and a novel freeze granulation method for the production of spherical particles suitable for the colloidal probe atomic force microscope (AFM)-technique is reported. We found that the interactions induced by the adsorption of the anionic acrylic ester–ethylene oxide (AAE–EO) copolymers can be described as electrosteric, with an electrostatic and steric contribution. The range of the steric repulsion varied between 1.5 and 5 nm and could be related to the length of the grafted ethylene oxide chains. The lignosulfonate also induced a significant steric contribution that could be related to a dense coil conformation of the adsorbed superplasticizer

  • 19. Kjellsen, Knut
    et al.
    Lagerblad, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Microstructure of tricalcium silicate and Portland cement system at middle periods of hydration-development of Hadley grains2007In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 37, no 1, p. 13-21Article in journal (Refereed)
    Abstract [en]

    The development of the microstructure of C3S paste and a Portland cement paste was studied between 7 and 24 h by means of backscattered electrons in a field-emission SEM. The course of hydration was measured by isothermal calorimetry. While the abundant occurrence of Hadley grains (hollow-shells) in Portland cement systems is well documented from a number of SEM and other microscopy studies, some earlier reports have noted that Hadley grains do not form in C3S or alite paste alone. This report shows evidence of Hadley grains in C3S paste, and follows their development from middle to late hydration stages. At around 10 h the microstructure with respect to Hadley grains were seen to develop in a very similar manner in C3S and cement. In both systems, a narrow gap often developed between the receding anhydrous cores and layer of reaction product enveloping the cores. By 1 day, Hadley grains had continued to develop only in the cement paste, where they became a prominent feature. Only small 'hollowed-out' hydration shells were observed in the C3S paste by 1 day. These were presumably reminiscences of the small gapped Hadley grains seen at the earlier hydration stages.

  • 20. Lindgård, Jan
    et al.
    Nixon, Philip J
    The EU “PARTNER” Project — European standard tests to prevent alkali reactions in aggregates: final results and recommendations2010In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 40, no 4 Special Issue, p. 611–635-Article in journal (Refereed)
  • 21.
    Peter, M. A.
    et al.
    University of Bremen, Postfach 330 440, 28334 Bremen, Germany.
    Muntean, Adrian
    University of Bremen, Postfach 330 440, 28334 Bremen, Germany.
    Meier, S. A.
    University of Bremen, Postfach 330 440, 28334 Bremen, Germany.
    Böhm, M.
    University of Bremen, Postfach 330 440, 28334 Bremen, Germany.
    Competition of several carbonation reactions in concrete: A parametric study2008In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 38, no 12, p. 1385-1393Article in journal (Refereed)
  • 22.
    Robison Fernlund, Joanne
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Image analysis method for determining 3-D shape of coarse aggregate2005In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 35, no 8, p. 1629-1637Article in journal (Refereed)
    Abstract [en]

    A 3-D method for particle shape determination of coarse aggregates using image analysis, IA, is presented. It is based on the measures the axial length of all three axis of every particle in a coarse aggregate sample. Two images of the entire aggregate sample are taken, in lying and standing positions. Since the particle's intermediate axes are measured in both images they can be used to couple the shortest and longest axial dimensions for each particle. The method allows an interpretation of length/thickness, length/width and width/thickness ratios of all the particles and is thus comparable to the flakiness and shape index tests.

  • 23.
    Roussel, Nicolas
    et al.
    University of Paris-Est, France.
    Gram, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Hållbara byggnadsverk.
    Cremonesi, Massimiliano
    Polytechnic University of Milan, Italy.
    Ferrara, Liberato
    Polytechnic University of Milan, Italy.
    Krenzer, Knut
    IAB Weimar GmbH, Germany.
    Mechtcherine, Viktor
    TU Dresden, Germany.
    Shyshko, Sergiy
    TU Dresden, Germany.
    Skocec, Jan
    Heidelberg Cement Technology Center GmbH, Germany.
    Spangenberg, Jon
    DTU Technical University of Denmark, Denmark.
    Svec, Oldrich
    DTU Technical University of Denmark, Denmark.
    Nyholm Thrane, Lars
    Danish Technological Institute, Denmark.
    Vasilic, Ksenija
    BAM Federal Institute for Material Research and Testing, Germany.
    Numerical simulations of concrete flow: A benchmark comparison2016In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 79, p. 265-271Article in journal (Refereed)
    Abstract [en]

    First, we define in this paper two benchmark flows readily usable by anyone calibrating a numerical tool for concrete flow prediction. Such benchmark flows shall allow anyone to check the validity of their computational tools no matter the numerical methods and parameters they choose. Second, we compare numerical predictions of the concrete sample final shape for these two benchmark flows obtained by various research teams around the world using various numerical techniques. Our results show that all numerical techniques compared here give very similar results suggesting that numerical simulations of concrete filling ability when neglecting any potential components segregation have reached a technology readiness level bringing them closer to industrial practice.

  • 24.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    The Severity of Plastic Shrinkage Cracking in Concrete: A New ModelIn: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948Article in journal (Other academic)
    Abstract [en]

    Plastic shrinkage cracking in concrete is mainly a physical process in which chemical reactions between cement and water do not play a decisive role. It is commonly believed that rapid and excessive moisture loss in the form of evaporation is the primary cause of the phenomenon. This paper presents a new model to estimate the severity of plastic shrinkage cracking in concrete based on initial setting time and the amount of the evaporated water from within the concrete. A number of experiments were performed under controlled ambient conditions, during which water-cement ratio, cement type and dosage of superplasticizer were altered. Results reported by other researchers were utilized, to check the validity of the proposed model. According to the outcomes, the model can predict the cracking severity of the fresh concrete with relative precision.

  • 25.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB, Sweden.
    Rheology of Cement Grouts: On the Critical Shear Rate and No-Slip Regime in the Couette Geometry2019In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948Article in journal (Refereed)
  • 26.
    Singh, Maneesh
    et al.
    Luleå tekniska universitet.
    Upadhayay, S.N.
    Department of Chemical Engineering and Technology, Banaras Hindu University.
    Prasad, P.M.
    Department of Metallurgical Engineering, Banaras Hindu University.
    Preparation of iron rich cements using red mud1997In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 27, no 7, p. 1037-1046Article in journal (Refereed)
    Abstract [en]

    Possibility of producing calcium sulfoaluminoferrite (SAF) (C4(A,F)3S over-bar )-calcium aluminoferrite (C4AF) based cements using lime + red mud + bauxite + gypsum has been investigated. The effects of composition, firing time and firing temperature on the properties of cements produced has been studied. The characteristics of the cements produced have been found to be strongly dependent on the raw mix composition and firing temperature but not so much on firing time. Some of these cements possess strengths comparable to and at times even more than ordinary Portland cement (OPC). Since the red mud used contains significant amount of titania, effect of titania on pure sulfoaluminate phase has also been studied.

  • 27.
    Tang, Luping
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Engineering expression of the ClinConc model for prediction of free and total chloride ingress in submerged marine concrete2008In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 38, no 8-9, p. 1092-1097Article in journal (Refereed)
  • 28.
    Wu, Min
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Geiker, Mette Rica
    Norwegian University of Science and Technology, Norway.
    A study of the water vapor sorption isotherms of hardened cement pastes: Possible pore structure changes at low relative humidity and the impact of temperature on isotherms2014In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 56, p. 97-105Article in journal (Refereed)
    Abstract [en]

    Using water vapor sorption isotherms measured by the “dynamic vapor sorption” (DVS) method, a resaturation study was conducted to investigate possible pore structure changes of hardened cement paste samples caused by the drying at low relative humidity during desorption measurements. The results indicate that either the relatively short term drying does not cause any microstructure changes or the pore structure of the hardened cement paste samples can be restored during the absorption process. Additionally, the temperature dependency of sorption isotherms was investigated using both hardened cement paste samples and a model material MCM-41. The pronounced impact of temperature on desorption isotherms of cement based materials as reported in literature was not found in this investigation. The results suggest that the differences between the sorption isotherms measured at different temperatures are mainly caused by the temperature dependent properties of water.

  • 29.
    Zandi, Kamyab
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Utgenannt, Peter
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Experimental study of the material and bond properties of frost-damaged concrete2011In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 41, no 3, p. 244-254Article in journal (Refereed)
1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf