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  • 1. 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.

  • 2.
    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    KTH, Superseded Departments, Civil and Architectural Engineering.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.

  • 3.
    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.

  • 4.
    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)
  • 5.
    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.

  • 6. 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.

  • 7.
    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.

  • 8.
    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)
    Abstract [en]

    The rheological properties of cement grouts play a key role in determining the final spread in grouted rock formations. In terms of flow properties, cement grouts are known to be complex thixotropic fluids, but their steady flow behavior is often described by the simple Bingham constitutive law. Due to their time dependent nature, the flow curves of cement grouts have been known to exhibit an unstable non-monotonic region, characterized by a negative slope below a critical shear rate. Within this paper, we focus on how this unstable region that is dominated by flow localization is affected by rheometer geometry and flow sweep measurement interval. We carried out controlled shear rate (CSR) flow sweeps on typical micro-cement grouts within different Couette geometries. Lastly, we discuss the effects of geometry and measurement interval on the resulting flow curves, with a focus on the critical shear rate that separates homogenous from non-homogeneous unstable flow.

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