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  • 1.
    Blandine, Feneuil
    et al.
    Aalto University, Concrete Technology Laboratory, Department of Civil and Structural Engineering, School of Engineering, Aalto University.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Cwircen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Erratum to: Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste2017In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 11, no 2, p. 255-255Article in journal (Refereed)
  • 2.
    Bohling, Daniel
    et al.
    Aalto University, Helsinki, Finland.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bond Strength between Glass Fiber Fabrics and Low Water-to-Binder Ratio Mortar: Experimental Characterization2018In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2018, article id 8197039Article in journal (Refereed)
    Abstract [en]

    Full utilization of mechanical properties of glass fiber fabric-reinforced cement composites is very limited due to a low bond strength between fibers and the binder matrix. An experimental setup was developed and evaluated to correlate the mortar penetration depth with several key parameters. The studied parameters included fresh mortar properties, compressive and flexural strengths of mortar, the fabric/mortar bond strength, fabric pullout strength, and a single-lap shear strength. Results showed that an average penetration of mortar did not exceed 100 µm even at a higher water-to-binder ratio. The maximum particle size of the used fillers should be below an average spacing of single glass fibers, which in this case was less than 20 µm to avoid the sieving effect, preventing effective penetration. The pullout strength was strongly affected by the penetration depth, while the single-lap shear strength was also additionally affected by the mechanical properties of the mortar.

  • 3.
    Bonath, Victoria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lintzén, Nina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fransson, Lennart
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Properties of ice from first-year ridges in the Barents Sea and Fram Strait2019In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 168, article id 102890Article in journal (Refereed)
    Abstract [en]

    First-year ice ridges are one of the main load scenarios that off-shore structures and vessels operating in ice-covered waters have to be designed for. For simulating such load scenarios, the knowledge gap on ice mechanical properties from the consolidated part of first-year ridges has to be filled. In total 410 small-scale uniaxial compression tests were conducted at different strain rates and ice temperatures on ice from the consolidated layer of 6 different first-year ridges in the sea around Svalbard. For the first time uniaxial tensile tests were performed on ice from first-year ridges using a new testing method. Ice strength was evaluated for different ice type, which are determined for each specimen based on a proposed ice classification system for ice from first-year ridges. 78% of all samples contained mixed ice with various compounds of brecciated columnar and granular ice. Ice strength of mixed ice showed isotropy, except for the samples containing mainly columnar ice crystals. For horizontal loading, mixed ice was stronger than columnar and granular ice. The residual strength of ductile ice depended on the strain rate. At 1.5% strain remained 70% of peak strength at 10−4 s−1 and 50% at 10−3 s−1. Ductile failure dominated for 75% of all mixed ice tests at 10−3 s−1 and − 10 °C. Ductile compressive strength was generally higher than brittle compressive strength for mixed ice. Brine volume was the main parameter influencing the tensile strength of the mixed ice which was between 0.14 MPa and 0.78 MPa measured at constant ice temperature of −10 °C.

  • 4.
    Bonath, Victoria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Petrich, Chris
    Northern Research Institute Narvik.
    Sand, Bjørnar
    Northern Research Institute Narvik.
    Fransson, Lennart
    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, Structural and Fire Engineering.
    Morphology, internal structure and formation of ice ridges in the sea around Svalbard2018In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 155, p. 263-279Article in journal (Refereed)
    Abstract [en]

    The results from 3 years of comprehensive field investigations on first-year ice ridges in the Arctic are presented in this paper. The scopes of these investigations were to fill existing knowledge gaps on ice ridges, gain understanding on ridge characteristics and study internal properties of ice. The ability of developing reliable simulations and load predictions for ridge-structure interactions is the final principal purpose, but beyond the scope of this paper. The presented data comprise ridge geometry, ice block dimensions from ridge sails, ice structure in the ridge and values on the ridge porosity and the degree of consolidation. The total ridge thickness conformed to other ridges studied in the same regions. The consolidated layer thickness was on average 2–3 times the level ice thickness. Minimum 33% and in average 90% of the ridge keel area was consolidated. The distribution of ice block sizes and block shapes within a ridge appears to be predictable. A new approach for deriving a possible ridging scenario and ridge age is presented. Different steps of the ridge building process were identified, which are in good agreement with earlier simulated ridging events. After formation of very thin lead ice between two floes deformation occurs through rafting and ridging until closure of the lead. Subsequently the adjacent level ice floe fractures proceeding ridge formation until ridging forces exceed driving forces. A time span of 10 days could be assessed for a possible ridge formation date, estimating the ridge age of the studied ridge located east of Edgeøya at 78° N to be 7 to 8 weeks.

  • 5.
    Buasiri, Thanyarat
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    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, Structural and Fire Engineering.
    State of the Art on Sensing Capability of Poorly or Nonconductive Matrixes with a Special Focus on Portland Cement–Based Materials2019In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 31, no 11Article in journal (Refereed)
    Abstract [en]

    Concrete is a well-established and the most used but also well-characterized building material in the world. However, many old and new-build structures suffer from premature failures due to extensive deterioration and decreased load-bearing capacity. Consequently, structural monitoring systems are essential to ensure safe usage of concrete structures within and beyond the designed life. Traditional monitoring systems are based on metallic sensors installed in crucial locations throughout the structure. Unfortunately, most of them have a relatively low reliability and very short life span when exposed to often very harsh environments. The ideal solution is therefore to develop a smart concrete having itself self-sensing capability. A number of studies show that conductive cementitious matrixes will undergo changes in their electrical resistivity with variations of stresses, strains or, developing microcracking. This can be used as a reliable tool to measure changes. This review provides a comprehensive overview of several non-conductive matrixes, with special focus on Portland cement based materials showing self-sensing capabilities by description of detection mechanisms, sensing capabilities, limitations and potential applications.  

  • 6.
    Buasiri, Thanyarat
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Krzeminski, Lukasz
    Silesian University of Technology, The Institute of Engineering Materials and Biomaterials, Poland.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Piezoresistive Load Sensing and Percolation Phenomena in Portland Cement Composite Modified with In-Situ Synthesized Carbon Nanofibers2019In: Nanomaterials, ISSN 2079-4991, Vol. 9, no 4, article id 594Article in journal (Refereed)
    Abstract [en]

    Carbon nanofibers (CNFs) were directly synthesized on Portland cement particles by chemical vapor deposition. The so-produced cements contained between 2.51–2.71 wt% of CNFs; depending on the production batch. Several mortar mixes containing between 0 and 10 wt% of the modified cement were produced and the electrical properties at various ages and the load sensing capabilities determined. The percolation threshold related to the electrical conductivity was detected and corresponded to the amount of the present CNFs, 0.271, 0.189, 0.135 and 0.108 wt%. The observed threshold depended on the degree of hydration of the Portland cement. The studied mortars showed a strong piezoresistive response to the applied compressive load reaching a 17% change of the electrical resistivity at an applied load of 3.5 MPa and 90% at 26 MPa. This initial study showed that the studied material is potentially suitable for future development of novel fully integrated monitoring systems for concrete structures.

  • 7.
    Carolin, Anders
    et al.
    Trafikverket, Luleå.
    Anderson, Robert
    Network Rail, London, United Kingdom.
    Heissenberger, Roman
    ÖBB, Wien, Austria.
    Hermosilla Carrasco, Carlos
    Acciona Technology, Madrid, Spain.
    Schewe, Britta
    Deutsche Bahn, Berlin, Germany.
    Nilimaa, jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwircen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Innovative Intelligent Management of Railway Bridges, In2Rail: A European Horizon 2020 Project2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, p. 2552-2561Conference paper (Refereed)
    Abstract [en]

    Innovative Intelligent Railways, In2Rail, is a European Horizon 2020 Project with the objective to enhance capacity, increase reliability and reduce Life Cycle Costs of European Railways. Bridges and Tunnels is the main focus in Work Package 4. The aim is to study, benchmark and further develop new Inspection Technologies in order to create more proactive maintenance procedures. In this paper some preliminary results are presented.

  • 8.
    Cnudde, V.
    et al.
    Department of Geology and Soil Science, Ghent University.
    Cwirzen, A.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Masschaele, B.
    Department of Geology and Soil Science, Ghent University.
    Jacobs, P. J S
    Department of Geology and Soil Science, Ghent University.
    Porosity and microstructure characterization of building stones and concretes2009In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 103, no 3-4, p. 76-83Article in journal (Refereed)
    Abstract [en]

    The microstructure of building materials greatly influences engineering properties like permeability, strength and durability. To determine this microstructure, different techniques were developed, each with its own limitations. The purpose of this study on concrete and natural building stones was to compare and to combine data obtained by X-ray computed micro-tomography (micro-CT), water absorption under vacuum and mercury intrusion porosimetry (MIP). Pore-size distribution curves ranging from 10 nm to 1 mm and total porosity results were obtained. Furthermore, micro-CT revealed the presence of an interfacial transition zone (ITZ) and of micro-cracks inside the aggregates of the concrete samples after mercury intrusion. Micro-CT visualized mercury inside large air bubbles within the concrete samples. Both micro-CT and MIP were compared and their respective advantages and disadvantages discussed. © 2008 Elsevier B.V. All rights reserved.

  • 9.
    Cwirzen, A.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    The effect of the heat-treatment regime on the properties of reactive powder concrete2007In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 19, no 1, p. 25-33Article in journal (Refereed)
    Abstract [en]

    The influence of the curing regime on the mechanical properties and microstructure of ultra-high-strength mortar was studied. Nine different curing procedures were applied in which the start and duration of the heat treatment were varied. The studied mortars had a water-to-binder ratio of 0·17 and additions of amorphous silica fume and fine quartz filler. The microstructure and microchemistry were investigated by electron scanning microscopy and mercury intrusion porosimetry. The results revealed that longer heating times increased the degree of hydration, refined the microstructure and resulted in higher ultimate compressive strength, Very late and very early application of the heat treatment caused a lower degree of hydration and a smaller long-term increase of compressive strength. The scanning electron microscopy investigation revealed the formation of one hydration rim around anhydrous cement particles and the presence of a hollow shell in all investigated specimens. © 2007 Thomas Telford Ltd.

  • 10.
    Cwirzen, A.
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, K.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Nasibulin, A. G.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Kaupinen, E. I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Mudimela, P. R.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Penttala, V.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    SEM/AFM studies of cementitious binder modified by MWCNT and nano-sized Fe needles2009In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 60, no 7, p. 735-740Article in journal (Refereed)
    Abstract [en]

    Several compositions of cement paste samples containing multiwalled carbon nanotubes were produced using a small-size vacuum mixer. The mixes had water-to-binder ratios of 0.25 and 0.3. Sulfate resistant cement has been used. The multiwalled carbon nanotubes were introduced as a water suspension with added surfactant admixtures. The used surfactant acted as plasticizing agents for the cement paste and as dispersant for the multiwalled carbon nanotubes. A set of beams was produced to determine the compressive and flexural strengths. The scanning electron microscope and atomic force microscope studies of fractured and polished samples showed a good dispersion of multiwalled carbon nanotubes in the cement matrix. The studies revealed also sliding of multiwalled carbon nanotubes from the matrix in tension which indicates their weak bond with cement matrix. In addition to multiwalled carbon nanotubes also steel wires covered with ferrite needles were investigated to determine the bond strength between the matrix and the steel wire. These later samples consisted of 15-mm-high cylinders of cement paste with vertically cast-in steel wires. As reference, plain steel wires were cast, too. The bond strength between steel wires covered with nano-sized Fe needles appeared to be lower in comparison with the reference wires. The scanning electron microscope studies of fractured samples indicated on brittle nature of Fe needles resulting in shear-caused breakage of the bond to the matrix. © 2008 Elsevier Inc. All rights reserved.

  • 11.
    Cwirzen, A.
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, K.
    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.
    Surface decoration of carbon nanotubes and mechanical properties of cement/carbon nanotube composites2008In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 20, no 2, p. 65-73Article in journal (Refereed)
    Abstract [en]

    The present study investigated the effects of the method of surface decoration on the wetability of multi-walled carbon nanotubes (MWCNTs) and the mechanical properties of the cement paste incorporating these dispersions. The results showed that stable and homogenous dispersions of MWCNTs in water can be obtained by using surface functionalisation combined with decoration using polyacrylic acid polymers. The cement paste specimens incorporating these dispersions revealed good workability and an increase in the compressive strength of nearly 50% even with only a small addition of the MWCNTs, namely 0-045-0-15% of the cement weight. These results indicate the existence of chemical bonds between the OH groups of the functionalised MWCNTs and probably the C-S-H phase of the cement matrix, which enhanced the transfer of stresses. A second method that was studied included decoration of MWCNTs with polyacrylic acid polymers and gum Arabic. These dispersions appeared to be homogeneous only for approximately 2 h after which a progressive sedimentation occurred. Good workability was found for the cement pastes produced with all of the dispersions; the only significant difference being the slower hydration of the cement incorporating gum Arabic. The mechanical properties of the cement pastes incorporating MWCNTs treated with polyacrylic polymers were unchanged.

  • 12.
    Cwirzen, A.
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, K.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Shandakov, D.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulina, L. I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulin, A. G.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Mudimela, P. R.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Kauppinen, E. I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Penttala, V.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Properties of high yield synthesised carbon nano fibres/portland cement composite2009In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 21, no 4, p. 141-146Article in journal (Refereed)
    Abstract [en]

    The compressive strength and electrical resistivity of hardened pastes produced either from nanomodified Portland sulfate-resistant cement (CHH) or a mixture of nanomodified and pristine sulfate-resistant cements were determined. The nanomodification included grow carbon nanotubes (CNTs) and carbon nanofibres (CNFs) on the cement particles. Pastes having a water-to-binder ratio of 0-5 were produced. The test results revealed that partial replacement of sulfate-resistant cement by CHH cement decreased the electrical resistivity of the 28 day old specimens but worsened the mechanical properties. The lower compressive strength was attributed to a lower degree of hydration of the CHH cement. The addition of a mixture of surfactants enabled the production of specimens consisting entirely of CHH cement. The hardened material obtained was characterised by a nearly doubled compressive strength in comparison with the reference specimens made from pristine sulfate-resistant cement. This was attributed to a high degree of hydration as well as reinforcing action of the CNTs and CNFs. The electrical resistivity was lowered by one order of magnitude classifying this material as a semiconductor.

  • 13.
    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.

  • 14.
    Cwirzen, Andrzej
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Controlling physical properties of cementitious matrixes by nanomaterials p12010In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 123-125, p. 639-642Article in journal (Refereed)
    Abstract [en]

    The majority of concrete used nowadays is based on matrixes formed by hydrating Portland cement. Latest developments in nanosciences introduced a new generation of nano-sized materials possessing often remarkable mechanical and physical properties. These materials can be also used to improve or alter the characteristics of the binder matrixes based on Portland cement. The results showed that mechanical properties such as compressive and flexural strength can be increased by up to 50% by addition of for example 0.23wt% of carbon nanotubes. Carbon nanotubes and carbon nanofibres and/or nanosilica appeared to improve also the frost resistance. Other properties, such as autogenous shrinkage decreased significantly after addition of carbon nanofibres. Nanosilica enabled an immense densification of the hydrated binder matrix, which in turn improved for instance the durability and mechanical properties. © (2010) Trans Tech Publications.

  • 15.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Engblom, Ronny
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Punkki, Jouni
    Consolis Technology Oy.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Effects of curing: Comparison of optimised alkali-activated PC-FA-BFS and PC concretes2014In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 66, no 6, p. 315-323Article in journal (Refereed)
    Abstract [en]

    The effects of curing on the mechanical properties, chemical composition, microstructure and shrinkage of optimised alkali-activated concretes (AACs) based on ternary mixtures of fly ash (FA), blast-furnace slag (BFS) and Portland cement (PC) were compared. Heat treatment was found to accelerate the early-age strength development of both the PC concrete and the AAC. The long-term strength of AAC was not adversely affected by the heat treatment after 90 d of dry curing. Water curing slightly enhanced the ultimate long-term strength of non-heat-treated AAC specimens but had barely any effect on the heat-treated specimens. Conversely, the dry-cured PC specimens showed a significant decrease in long-term compressive strength. The ultimate drying shrinkage of the PC concrete was lower compared with the AAC, independent of the type of applied curing. In the case of AAC, the drying shrinkage was significantly decreased by the application of heat treatment while water curing did not have any measurable effect. Conversely, the drying shrinkage of AAC cured at ambient temperatures was decreased with the application of water curing. Compared with the PC concrete, the microstructure of the AAC samples was denser and more homogeneous without visible microcracking of the binder matrix. The dominant phases were geopolymer and calcium silicate hydrate (C-S-H) gels intermixed with probably sodium and aluminium ions and crystalline inclusions of zeolitic hydroxysodalite. A large amount of unreacted FA and BFS was observed in the hardened binder matrix of the AAC specimens. At the same time, no anhydrous PC was observed, thus indicating its extensive dissolution and contribution to the formation of the modified C-S-H gel.

  • 16.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Effects of reactive magnesia on microstructure and frost durability of portland cement-based binders2013In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 25, no 12, p. 1941-1950Article in journal (Refereed)
    Abstract [en]

    The effects of portland cement (PC) replacement with magnesia (reactive magnesium-oxide) on properties of PC-based pastes, mortars, and concretes were investigated. The research included determination of mechanical properties and frost durability in addition to studies of the microstructure and microchemistry. The mortar and paste mixtures contained from 10-80 weight percent (wt%) replacement of PC by magnesia and had water to cementitious-binder ratios from 0.4-0.7, whereas concretes contained from 5-10 wt% magnesia and had a water to cementitious-binder ratio of 0.53. Replacement of PC by magnesia had adverse effects on the mechanical properties and frost durability. The magnesia reduced microcracking of the binder matrix in comparison with pastes containing only PC. The primary hydration product of magnesia was brucite in addition to regular hydration phases of PC. The amount of formed portlandite was increased. Magnesia caused densification of the microstructure but also increased the capillary porosity, resulting in lower frost-durability. © 2013 American Society of Civil Engineers.

  • 17.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Enhancement of Frost Durability by Application of Nanomaterials2010In: Additions improving properties of concrete: AdIPoC / [ed] Wolfgang Brameshuber, Bagneux: Rilem publications, 2010, p. 307-313Conference paper (Refereed)
    Abstract [en]

    The effect of carbon nanotubes (CNT), carbon nanofibers (CNF) and nano-sized silica (NS) on the frost durability of mortars was investigated. The test specimens were produced using Portland cement as binder and water to binder ratios of 0.5 and 0.33. CNT and CNF were added as water dispersion with superplasticizers. The NS was intermixed with micro silica and added as slurry. The frost durability was determined by a modified CIF method. The results showed that in the case of addition of nano-sized fibers a positive effect can be only found if the binder matrix is homogenous and dense. The combination of CNTs and NS resulted in the lack of any frost damage even after 180 freeze-thaw cycles.

  • 18.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    The effect of carbon nano- and microfibers on strength and residual cumulative strain of mortars subjected to freeze-thaw cycles2013In: Journal of Advanced Concrete Technology, ISSN 1346-8014, Vol. 11, no 3, p. 80-88Article in journal (Refereed)
    Abstract [en]

    The strength and development of residual strain of normal strength mortars subjected to freeze-thaw cycles incorporating carbon nanotubes (CNTs) and carbon microfibers (CMF) were studied. The workability was influenced by the fiber type, the dispersion method, and the amount of fibers. The obtained results showed that the measured flexural strength increased only in the case of mortars incorporating CMFs. The compressive strength remained unchanged in the case of mortars containing CMFs and was slightly lower when CNTs were present. The residual strain due to freeze-thaw cycles was lowered in comparison with reference mortar only when incorporating CMFs. The obtained results confirmed that in order to utilize the outstanding mechanical properties of CNTs the binder matrix must be very homogenous to provide sufficient contact area for stress transfer. The used water to binder ratio was sufficiently low only for long CMFs, which were able to bridge numerous weak inclusions present on the binder matrix. © 2013 Japan Concrete Institute.

  • 19.
    Cwirzen, Andrzej
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, Karin
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Nasibulina, Larisa I.
    Department of Applied Physics, Aalto University, Department of Applied Physics and Center for New Materials, Laboratory of Physics, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Shandakov, Sergey D.
    Department of Applied Physics and Center for New Materials, Aalto University, Laboratory of Carbon NanoMaterials, Kemerovo State University, Department of Applied Physics, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulin, Albert G.
    Department of Applied Physics, Aalto University, Department of Applied Physics and Center for New Materials, Centre for New Materials, Laboratory of Physics, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Kauppinen, Esko I.
    Department of Applied Physics, Aalto University, VTT Biotechnology, Laboratory of Physics, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Mudimela, Prasantha R.
    Department of Applied Physics and Center for New Materials, Aalto University, Centre for New Materials, Department of Applied Physics, Laboratory of Physics, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Penttala, Vesa
    Department of Civil and Structural Engineering, Aalto University, Department of Structural Engineering, Laboratory of Building Materials Technology, Laboratory of Building Materials, NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    CHH Cement Composite2009In: Nanotechnology in Construction 3: Proceedings of the NICOM3 / [ed] Zdeněk Bittnar ; Peter J.M. Bartos; Jiří Němeček; Vit Šmilauer; Jan Zeman, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2009, p. 181-185Conference paper (Refereed)
    Abstract [en]

    The compressive strength and electrical resistivity for hardened pastes produced from nanomodified Portland SR cement (CHH- Carbon Hedge Hog cement) were studied. The nanomodification included growing of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on the cement particles. Pastes having water to binder ratio of 0.5 were produced. The obtained hardened material was characterized by increased compressive strength in comparison with the reference specimens made from pristine SR cement, which was attributed to reinforcing action of the CNTs and CNFs. The electrical resistivity of CHH composite was lower by one order of magnitude in comparison with reference Portland cement paste

  • 20.
    Cwirzen, Andrzej
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Metsäpelto, Lari
    MSc, YIT Infra Oy, Helsinki, Finland.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Interaction of Magnesia with Limestone-Metakaolin-Calcium Hydroxide Ternary Alkali-Activated Systems2018In: Advances in Materials Science and Engineering, ISSN 1687-8434, E-ISSN 1687-8442, Vol. 2018, article id 1249615Article in journal (Refereed)
    Abstract [en]

    The effect of magnesia on ternary systems composed of limestone, metakaolin and calcium hydroxide, alkali activated with sodium silicate, sodium hydroxide, and sodium sulphate was studied by determination of the compressive strength, X-ray powder diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). Pastes activated with sodium silicate and sodium sulphate showed strength regression caused by a formation of an unstable prone to cracking geopolymer gel. The presence of magnesia in sodium hydroxide-activated system hindered this trend by promoting a formation of more stable crystalline phases intermixed with brucide. In general, magnesia densified the binder matrix by promoting a formation of amorphous phases while sodium hydroxide produced the most porous microstructure containing high amount of crystalline phases.

  • 21.
    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.

  • 22.
    Cwirzen, Andrzej
    et al.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Penttala, Vesa
    Department of Civil and Structural Engineering, Aalto University, Department of Structural Engineering, Laboratory of Building Materials Technology, Laboratory of Building Materials.
    Vornanen, C.
    Aalto University.
    RPC mix optimization by determination of the minimum water requirement of binary and polydisperse mixtures2005In: ISISS 2005: Innovation & Sustainability of Structures / [ed] Z. Lu; A. Li; Z. Wu; S. Meng, 2005, Vol. 1-3, p. 2191-2201Conference paper (Refereed)
    Abstract [en]

    Reactive powder concrete (RPC) is an ultra high performance material which development was strongly associated with the maximization of the packing density. This paper presents an alternative approach for the optimization of the mix design of RPC by using the determination of the water demand of binary, ternary and polydisperse mixes. Measurements of the water demand of quartz/sand and quartz/sand/cement/silica fume mixes were performed. The control mixes-having water to binder ratio of 0.187, 25% of silica fume and 5% of superplasticizer measured from cement content-were produced for the assessment of fresh concrete properties and compressive strength. The concretes were heat-treated at 90 degrees C. The results showed that maximum compressive strength was obtained in concretes having binary quartz/sand mixes characterized by the highest packing density. The best rheorogical properties were obtained in mixes, which had the highest packing density when measured on polydisperse mixes containing all RPC components.

  • 23.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Provis, John L.
    Department of Chemical & Biomolecular Engineering, University of Melbourne.
    Penttala, Vesa
    Department of Civil and Structural Engineering, Aalto University.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    The effect of limestone on sodium hydroxide-activated metakaolin-based geopolymers2014In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 66, p. 53-62Article in journal (Refereed)
    Abstract [en]

    Blends of metakaolin and limestone can be alkali-activated with NaOH to form solid binders, which show relatively low strength but offer potential as a model system by which the reaction processes of more complex systems can be better understood. The effects of curing procedure, limestone content and alkalinity of the activator are able to be related to the mineralogy, mechanical properties and microstructure of hardened pastes. The presence of limestone enhances the release of Al and Si ions from metakaolin, with the Al released in the early stages of the reaction being bound into AFm-type phases. Dissolution of LS is slightly higher when a lower alkalinity sodium hydroxide activator is used. The heat treatment of pastes activated with 3 M NaOH solution resulted in a lower extent of reaction of limestone, while with 5 M solution, heat-curing at early age resulted in more reaction. The main alkali-activation product in metakaolin-limestone-NaOH pastes is a geopolymer gel with inclusions of unreacted metakaolin, limestone particles, zeolite A, and AFm phases, with different zeolites such as faujasite-like and hydrosodalite phases also identified at higher reaction temperatures. © 2014 Elsevier Ltd. All rights reserved.

  • 24.
    Cwirzen, Andrzej
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Sztermen, P.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Habermehl-Cwirzen, Karin
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Effect of baltic seawater and binder type on frost durability of concrete2014In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 26, no 2, p. 275-282Article in journal (Refereed)
    Abstract [en]

    The effects of Baltic seawater on frost durability of PC concretes using sulfate resistant portland cement and combination of rapid hardening portland cement with silica fume were studied. The freeze-thaw cycles were performed on specimens exposed to the Baltic seawater, 3% sodium chloride solution and deionized water. The freeze-thaw cycles appeared to cause the most extensive internal damage in specimens based on sulfate resistant cement (SR) and exposed to seawater. The most extensive surface scaling was observed in the case of concretes containing silica fume and exposed to deicing salts. Based on the thermo gravimetric and X-ray diffraction analyses it was concluded that extensive internal damage of concrete based on SR was caused by changes of the microstructure due to secondary formation of ettringite, carbonation, and formation of calcite. The results showed also that low C3A content of the SR did not fully mitigate formation of secondary ettringite during freeze-thaw cycles. A combination of rapid hardening portland cement and silica fume appeared to form more frost resistant concrete when exposed to seawater. © 2014 American Society of Civil Engineers.

  • 25.
    Feneuil, Blandine
    et al.
    Aalto University, Concrete Technology Laboratory, Department of Civil and Structural Engineering, School of Engineering, Aalto University.
    Habermehl-Cwirzen, Karin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. 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, Structural and Construction Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste2016In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 10, no 2, p. 224-235Article in journal (Refereed)
    Abstract [en]

    In this experimental study, carbon nanotubes (CNTs) and carbon nanofibers (CNFs) were dispersed by intensive sonication in water in the presence of superplasticizer and subsequently mixed with Portland cement with water/ cement ratios varying between 0.3 and 0.4. The autogenous shrinkage in the fresh stage was investigated. The CNTs and CNFs were characterized by high resolution scanning electron microscopy (SEM) and the hydrated pastes were studied by X-ray diffraction and SEM. The results showed a reduction of the autogenous shrinkage by 50% for pastes containing small amounts (0.01 wt%) of nanomaterials. Higher additions appeared to be less effective. The highest reduction of shrinkage was observed for carbon nanofibers which were long, rather straight and had diameters of around 200 nm. The result showed that the addition of nanomaterials accelerated the hydration processes especially in the early stages of hydration. The effect was the most pronounced in the case of functionalized nanotubes. The proposed mechanism resulting in the reduction of the autogenous shrinkage was a combination of nano-reinforcing effects, alterations of hydration and microstructure of the hydrated matrix.

  • 26.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A theoretical study on optimal packing in mortar and paste2019In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605Article in journal (Refereed)
    Abstract [en]

    Packing density of particles is regarded as a key factor affecting workability of cementitious mixtures. While the value can be easily measured, and several models exist for estimating the parameter, no generally accepted definition exist for the optimal packing. Current study aims at exploring the concept of optimal packing in mortars and paste using particle packing and excess water layer theories. A semiempirical method is used for calculating water demand of mixtures based on their specific surface area. The approach allows for estimating optimal packing considering water demand and water to cement ratio of mixtures in addition to packing density. 

  • 27.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Lulea university of technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Betongindustri AB, Stockholm, Sweden.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Effect of water film thickness on the flow in conventional mortars and concrete2019In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 3, article id 62Article in journal (Refereed)
    Abstract [en]

    Mortar and concrete can be divided into two phases of solids and water where water fills the voids between the grains and also coats the surface of particles. The current study investigates the influence of the thickness of coating water on flow spread of mortars and concretes. The article aims at correlating consistency of concretes to consistency of mortars. It was found that the flow behavior of granular mixtures can be directly related to the average water film thickness that envelops the particles. The concept was tested on mortar and concrete mixtures with different cement types, aggregate grading, aggregate shape, fineness and proportioning; proving water film thickness to be the most critical parameter affecting the flow. The results of the study indicate the possibility of predicting the flowability of mixtures by knowing the enveloping water film thickness. In addition, the relation between flowability of mixtures measured in different sizes of slump cone is explored to enable translating flow of mortars measured in mini-slump cone to flow of concrete obtained from Abram’s cone.

  • 28.
    Ghasemi, Yahya
    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.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Exploring the relation between the flow of mortar and specific surface area of its constituents2019In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 211, p. 492-501Article in journal (Refereed)
    Abstract [en]

    Mortars can be studied as mixtures of solid and flowable phases. The volume of the flowable phase required for deformation depends on the solid phase surface area according to excess layer theories. This paper examines the relation between the specific surface area of constituents in mortars and their flow. The flowable phase volume was divided by the solid phase surface area to obtain the layer thickness surrounding the surface of the particles. The results suggested that the amount of water and paste needed to ensure flow could be estimated from the packing density and specific surface area of the particles.

  • 29.
    Ghasemi, Yahya
    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.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Quantification of the shape of particles for calculating specific surface area of powders2016In: RILEM publication S.A.R.L, Denmark, 2016, Vol. 115, p. 31-41Conference paper (Refereed)
    Abstract [en]

    The concepts of particle packing and water/paste layer theory are commonly used for basis of concrete mix design models. While particle packing insists on achieving fewer voids in aggregate matrix by adding fine aggregate, water/paste layer theories state that increasing the amount of fines will lead to higher water demand since the specific surface area of particles will increase. In order to calculate the thickness of excess paste, it is essential to quantify the shape of particles. However, there are uncertainties regarding how the various shape parameters would affect the packing and specific surface, mainly because up to now many of the shape parameters are not yet clearly defined and there are no commonly accepted methods for their measurement. In addition, the term “shape” needs to be defined, some research suggest that for obtaining an appropriate shape factor several parameters need to be measured e.g. flakiness, elongation, sphericity, convexity etc. The paper aims to derive a shape factor based on variation of packing from the packing of ideal spheres with the same particle size distribution as the studied aggregate and to apply the shape factor to calculate an approximate specific surface area value.

  • 30.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mats, Emborg
    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, Structural and Fire Engineering.
    Estimation of specific surface area of particles based on size distribution curve2018In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 10, p. 533-540Article in journal (Refereed)
    Abstract [en]

    Workability in the fresh state is one of the most important factors in design and production of concrete and can be related to the water demand of the mixture, which in addition to other factors is a function of the particle shape of aggregates and binders and their specific surface area. While it is known that the shape of fine particles has a significant effect on the water demand, there are uncertainties regarding how the various shape parameters would affect the specific surface area, mainly because up to now many of the shape parameters have not yet been clearly defined and there are no commonly accepted methods for their measurement and/or estimation. In this research, the actual particle shapes were replaced with regular convex polyhedrons to calculate the total specific surface area using the size distribution curves of the samples. The obtained results indicate that while, in some cases, the assumption of a spherical particle shape leads to an acceptable estimation of the specific surface area when compared with Blaine test results, the specific surface area of powders with more angular particles could be calculated more accurately with the assumption of a polyhedron shape rather than a sphere.

  • 31.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Rajczakowska, Magdalena
    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.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography2018In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763XArticle in journal (Refereed)
    Abstract [en]

    The specific surface area (SSA) of constituents in a concrete mixture has a significant effect on its workability in fresh state. Excess layer theories relate the SSA to the flow behaviour of mixtures and can be used as part of an approach to mix design. However, measurement of SSA is complex and includes several issues, and thus is commonly replaced by mathematical estimation of the parameter. The mathematical approximation of surface area is based on the assumption of a spherical shape for the particles, which leads to failure of taking into account the effect of shape and the square–cube law. The article explores the possibility of replacing the assumption of a spherical shape with that of Platonic solids as the representative shape to account for the angularity of aggregates. The calculation was conducted based on information on the particle size distribution (PSD) obtained from dry sieving method. A calculated surface area on the assumption of a dodecahedron shape for natural aggregates and a cubical shape for crushed aggregates showed good agreement with SSA measurements conducted by X-ray microtomography. Furthermore, the effect of changes in PSD on the accuracy of the approach was also studied. It was found that the estimated value of SSA was improved in comparison with the traditional way of calculation on the assumption of a spherical shape.

  • 32.
    Habermehl-Cwirzen, Karin
    et al.
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Curtain, Roger
    Bio21 Molecular Science and Biotechnology Institute.
    Penttala, Vesa
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Provis, John
    Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, AUS-University of Melbourne.
    Gordon, Laura
    Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, AUS-University of Melbourne.
    Cwirzen, Andrzej
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Sustainable straw-based cementitious building materials2012In: fib Symposium 2012: Concrete Structures for Sustainable Community - Proceedings / [ed] Dirch H. Bager; Johan Silfwerbrand, Stockholm: Swedish Concrete Association , 2012, p. 477-480Conference paper (Refereed)
    Abstract [en]

    New classes of sustainable cementitious materials are needed to improve the environmental impact of cement-based building materials. This study describes the recent work carried out on cementitious materials made with various straw-fibre based additions. The straw was used as unprocessed and chemically processed. The chemical processing enabled fibre extraction down to the micro and nano scale. The different fibres, before and after processing, as well as the fibre-hydrated cement paste composites were characterized and the mechanical properties of the different materials were determined.

  • 33.
    Horoshenkov, K. V.
    et al.
    Department of Civil and Environmental Engineering, University of Bradford.
    Hughes, D. C.
    Department of Civil and Environmental Engineering, University of Bradford.
    Cwirzen, A.
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    The sound speed and attenuation in loose and consolidated granular formulations of high alumina cements2003In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 64, no 2, p. 197-212Article in journal (Refereed)
    Abstract [en]

    Clinkers of high alumina cements are separated into three granular formulations with particle sizes in the range 0.6-0.71 mm, 0.71-1.18 mm and greater than 1.18 mm. These are used to manufacture consolidated samples of porous concrete in an autoclave. The acoustic and microscopic properties of loose and consolidated porous samples of concrete are investigated using both experimental methods and mathematical modelling. Values of porosity, flow resistivity, tortuosity and parameters of the pore size distribution are determined and used to predict closely the sound speed, acoustic attenuation and normal incidence absorption coefficient of these materials. It is shown that high alumina cements do not require additional binders for consolidation and that the structural bonds in these cements are developed quickly between individual clinkers in the presence of water. The hydration product build-up during the consolidation process is insignificant which ensures good acoustic performance of the consolidated samples resulting from a sufficient proportion of the open pores. The value of porosity in the consolidated samples was found to be around 40%, which is close to that measured in some commercial acoustic absorbers. This work provides a foundation for the development of acoustically efficient and structurally robust materials, which can be integrated in environmentally sustainable concrete and masonry structures. © 2002 Elsevier Science Ltd. All rights reserved.

  • 34.
    Humad, Abeer
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    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, Structural and Fire Engineering.
    Effects of fineness and chemical composition of blast furnace slag on properties of alkali-activated binder2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 20, article id 3447Article in journal (Refereed)
    Abstract [en]

    Abstract: The effects of fines and chemical composition of three types of ground granulated blast furnace slag (GGBFS) on various concrete properties were studied. Those studied were alkali activated by liquid sodium silicate (SS) and sodium carbonate (SC). Flowability, setting times, compressive strength, efflorescence, and carbonation resistance and shrinkage were tested. The chemical composition and microstructure of the solidified matrixes were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) coupled with EDX analyser. The results showed that the particle size distribution of the slags and the activator type had significantly stronger effects on all measured properties than their chemical composition. The highest compressive strength values were obtained for the finest slag, which having also the lowest MgO content. SC-activated mortar produced nearly the same compressive strength values independently of the used slag. The most intensive efflorescence and the lowest carbonation resistance developed on mortars based on slag containing 12% of MgO and the lowest fineness. The slag with the highest specific surface area and the lowest MgO content developed a homogenous microstructure, highest reaction temperature and lowest drying shrinkage. Thermogravimetric analysis indicated the presence of C-(A)-S-H, hydrotalcite HT, and carbonate like-phases in all studied mortars.

  • 35.
    Humad, Abeer
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Civil Engineering Department, Babylon University, Hillah, Iraq.
    Kothari, Ankit
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Provis, John L.
    Department of Materials Science and Engineering, University of Sheffield, Sheffield, United Kingdom.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    The Effect of Blast Furnace Slag/Fly Ash Ratio on Setting, Strength, and Shrinkage of Alkali-Activated Pastes and Concretes2019In: Frontiers in Materials, ISSN 2296-8016, Vol. 6, no 9Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to determine the effects of partial fly ash substitution in to a series of alkali-activated concrete based on a high-MgO blast furnace slag BFS. Mixes were activated with various amounts of sodium silicate at alkali modulus (mass ratio SiO2/Na2O) values of 1.0, 0.5, and 0.25. The results showed that, an increase in the fly ash content extended the initial setting time but had very little effect on the final setting time, although the early age compressive strength was decreased. The fly ash addition had no effect on the drying shrinkage but lowered the autogenous shrinkage. The mixes activated with sodium silicate at a lower alkali modulus showed a significantly higher autogenous shrinkage but lower drying shrinkage values. Severe micro cracking of the binder matrix was observed only for mixes without fly ash, activated with sodium silicate solution at higher alkali modulus. Decreasing the alkali modulus resulted in a higher autogenous shrinkage, less micro cracking and a more homogenous structure due to more extensive formation of sodium-aluminate-silicate-hydrate gel (N-A-S-H), promoted by the addition, and more extensive reaction of the fly ash.

  • 36.
    Humad, Abeer M.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Babylon Univ, Civil Engn Dept, Babylon, Iraq.
    Provis, John L.
    Univ Sheffield, Dept Mat Sci & Engn, Sheffield, S Yorkshire, England.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Alkali activation of a high MgO GGBS: fresh and hardened properties2018In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 24, p. 1256-1264Article in journal (Refereed)
    Abstract [en]

    In this study, concretes and pastes were produced from a high magnesium oxide (MgO) ground granulated blast furnace slag (magnesium oxide content 16.1 wt%) by alkali activation with various amounts and combinations of sodium carbonate and sodium silicate. Sodium carbonate activators tended to reduce slump compared to sodium silicate at the same dose, and, in contrast to the literature for many blast furnace slags with more moderate magnesium oxide, to shorten the initial and final setting times in comparison with concretes activated by sodium silicate for dosages less than 10 wt%. Higher heat curing temperatures and the use of larger dosages of alkali activators resulted in higher early-age compressive cube strength values. The X-ray diffraction analysis of 7 and 28 d old pastes activated with sodium carbonates revealed formation of gaylussite, calcite, nahcolite and calcium-aluminium-silicate-hydrate (C-A-S-H) gel. Curing at 20 degrees C appeared to promote dissolution of gaylussite and calcite, while heat curing promoted their replacement with C-A-S-H, which also resulted in higher ultimate cube compressive strength values. Conversely, mixes activated with sodium silicate contained less crystalline phases and more disordered gel, which strengthened the binder matrix.

  • 37.
    Matsakas, Leonidas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karnaouri, Anthi C
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Formation of Lignin Nanoparticles by Combining Organosolv Pretreatment of Birch Biomass and Homogenization Processes2018In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, no 7, article id 1822Article in journal (Refereed)
    Abstract [en]

    Valorization of lignocellulosic biomass into a biorefinery scheme requires the use of all biomass components; in this, the lignin fraction is often underutilized. Conversion of lignin to nanoparticles is an attractive solution. Here, we investigated the effect of different lignin isolation processes and a post-treatment homogenization step on particle formation. Lignin was isolated from birch chips by using two organosolv processes, traditional organosolv (OS) and hybrid organosolv-steam explosion (HOS-SE) at various ethanol contents. For post-treatment, lignin was homogenized at 500 bar using different ethanol:water ratios. Isolation of lignin with OS resulted in unshaped lignin particles, whereas after HOS-SE, lignin micro-particles were formed directly. Addition of an acidic catalyst during HOS-SE had a negative impact on the particle formation, and the optimal ethanol content was 50⁻60% v/v. Homogenization had a positive effect as it transformed initially unshaped lignin into spherical nanoparticles and reduced the size of the micro-particles isolated by HOS-SE. Ethanol content during homogenization affected the size of the particles, with the optimal results obtained at 75% v/v. We demonstrate that organosolv lignin can be used as an excellent starting material for nanoparticle preparation, with a simple method without the need for extensive chemical modification. It was also demonstrated that tuning of the operational parameters results in nanoparticles of smaller size and with better size homogeneity.

  • 38.
    Mudimela, Prasantha R.
    et al.
    NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulina, Larisa I.
    NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulin, Albert G.
    NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Cwirzen, Andrzej
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Valkeapää, Markus
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, Karin
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Malm, Jari E M
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Karppinen, Maarit J.
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Penttala, Vesa
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Koltsova, Tatiana S.
    Material Science Faculty, State Polytechnical University.
    Tolochko, Oleg V.
    Material Science Faculty, State Polytechnical University.
    Kauppinen, Esko I.
    NanoMaterials Group, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Synthesis of carbon nanotubes and nanofibers on silica and cement matrix materials2009In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2009, article id 526128Article in journal (Refereed)
    Abstract [en]

    In order to create strong composite materials, a good dispersion of carbon nanotubes (CNTs) and nanofibers (CNFs) in a matrix material must be obtained. We proposed a simple method of growing the desirable carbon nanomaterial directly on the surface of matrix particles. CNTs and CNFs were synthesised on the surface of model object, silica fume particles impregnated by iron salt, and directly on pristine cement particles, naturally containing iron oxide. Acetylene was successfully utilised as a carbon source in the temperature range from 550 to 750 °C. 5-10 walled CNTs with diameters of 10-15nm at 600 °C and 12-20nm at 750 °C were synthesised on silica particles. In case of cement particles, mainly CNFs with a diameter of around 30nm were grown. It was shown that high temperatures caused chemical and physical transformation of cement particles. © 2009 Prasantha R. Mudimela et al.

  • 39.
    Nasibulin, Albert G.
    et al.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Shandakov, Sergey D.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulina, Larisa I.
    Cwirzen, Andrzej
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Mudimela, Prasantha R.
    Department of Applied Physics, Aalto University.
    Habermehl-Cwirzen, Karin
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Grishin, Dmitrii A.
    Mendeleev University of Chemical Technology.
    Gavrilov, Yuriy V.
    Mendeleev University of Chemical Technology.
    Malm, J. E M
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Tapper, Unto
    VTT Biotechnology.
    Tian, Ying
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Penttala, Vesa
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Karppinen, Maarit J.
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Kauppinen, Esko I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    A novel cement-based hybrid material2009In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, article id 23013Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) are known to possess exceptional tensile strength, elastic modulus and electrical and thermal conductivity. They are promising candidates for the next-generation high-performance structural and multi-functional composite materials. However, one of the largest obstacles to creating strong, electrically or thermally conductive CNT/CNF composites is the difficulty of getting a good dispersion of the carbon nanomaterials in a matrix. Typically, time-consuming steps of purification and fimctionalization of the carbon nanomaterial are required. We propose a new approach to grow CNTs/CNFs directly on the surface of matrix particles. As the matrix we selected cement, the most important construction material. We synthesized in a simple one-step process a novel cement hybrid material (CHM), wherein CNTs and CNFs are attached to the cement particles. The CHM has been proven to increase 2 times the compressive strength and 40 times the electrical conductivity of the hardened paste, i.e. concrete without sand. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

  • 40.
    Nasibulina, Larisa I.
    et al.
    Department of Applied Physics, Aalto University School of Science.
    Anoshkin, Ilya V.
    Department of Applied Physics, Aalto University School of Science.
    Nasibulin, Albert G.
    Department of Applied Physics, Aalto University School of Science.
    Cwirzen, Andrzej
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Penttala, Vesa
    Department of Civil and Structural Engineering, Aalto University, School of Engineering, Espoo.
    Kauppinen, Esko I.
    Department of Applied Physics, Aalto University School of Science.
    Effect of carbon nanotube aqueous dispersion quality on mechanical properties of cement composite2012In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2012, article id 169262Article in journal (Refereed)
    Abstract [en]

    An effect of the quality of carbon nanotube (CNT) dispersions added to cement on paste mechanical properties has been studied. High-quality dispersions of few-walled CNT (FWCNTs) were produced in two steps. First, FWCNTs were functionalized in a mixture of nitric and sulfuric acids (70wt. and 96wt., resp.) at 80°C. Second, functionalized FWCNTs were washed out by acetone to remove carboxylated carbonaceous fragments (CCFs) formed during CNT oxidation. Mechanical test results showed 2-fold increase in the compressive strength of the cement paste prepared from the dispersion of acetone-washed functionalized FWCNTs, which is believed to occur due to the chemical interaction between cement matrix and functional groups (-COOH and -OH). Utilisation of unwashed FWCNTs led to a marginal improvement of mechanical properties of the cement pastes, whereas surfactant-treated functionalized FWCNT dispersions only worsened the mechanical properties. Copyright © 2012 Larisa I. Nasibulina et al.

  • 41.
    Nasibulina, Larisa I.
    et al.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Anoshkin, Ilya V.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Shandakov, Sergey D.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Nasibulin, Albert G.
    Department of Applied Physics and Center for New Materials, Aalto University.
    Cwirzen, Andrzej
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Mudimela, Prasantha R.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Habermehl-Cwirzen, Karin
    Laboratory of Building Materials Technology, Faculty of Engineering and Architecture, Helsinki University of Technology, Espoo.
    Malm, Jari E M
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Koltsova, Tatiana S.
    Material Science Faculty, State Polytechnical University.
    Tian, Ying
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Vasilieva, Ekaterina S.
    Material Science Faculty, State Polytechnical University.
    Penttala, Vesa
    Laboratory of Building Materials Technology, Aalto University.
    Tolochko, Oleg V.
    Material Science Faculty, State Polytechnical University.
    Karppinen, Maarit J.
    Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, Espoo.
    Kauppinen, Esko I.
    Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo.
    Direct synthesis of carbon nanofibers on cement particles2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2142, p. 96-101Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) and nanofibers (CNFs) are promising candidates for the next generation of high-performance structural and multifunctional composite materials. One of the largest obstacles to creating strong, electrically or thermally conductive CNT-CNF composites is the difficulty of getting a good dispersion of the carbon nanomaterials in a matrix. Typically, time-consuming steps are required in purifying and functionalizing the carbon nanomaterial. A new approach under which CNTs-CNFs are grown directly on the surface of matrix and matrix precursor particles is proposed. Cement was selected as the precursor matrix, since it is the most important construction material. A novel cement hybrid material (CHM) was synthesized in which CNTs and CNFs are attached to the cement particles by two different methods: screw feeder and fluidized bed reactors. CHM has been proved to increase the compressive strength by two times and the electrical conductivity of the hardened paste by 40 times.

  • 42.
    Niewiadomski, Pawel
    et al.
    Faculty of Civil Engineering, Wroclaw University of Technology.
    Cwirzen, Andrzej
    Aalto University, Espoo.
    Hola, Jerzy
    Faculty of Civil Engineering, Wroclaw University of Technology.
    The influence of an additive in the form of selected nanoparticles on the physical and mechanical characteristics of self-compacting concrete2015In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 111, p. 601-606Article in journal (Refereed)
    Abstract [en]

    The influence of nanoparticle additives on the physical and mechanical characteristics of hardened self-compacting concrete (SCC) was studied. Research included SCC concretes modified with different amounts of SiO2, TiO2 and Al2O3 nanoparticle additives and one reference concrete made without nanoparticles. Rheological properties, microstructure and compressive strength were determined. The obtained results showed that SiO2 and Al2O3 additions worsened the workability while the compressive strength was increased in the case of SiO2 addition. All studied nanomaterials densified the microstructure of the hydrated binder matrix

  • 43.
    Niewiadomski, Paweł
    et al.
    Faculty of Civil Engineering, Wroclaw University of Science and Technology.
    Hola, Jerzy
    Faculty of Civil Engineering, Wroclaw University of Science and Technology.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Study on properties of self-compacting concrete modified with nanoparticles2018In: Archives of Civil and Mechanical Engineering, ISSN 1644-9665, Vol. 18, no 3, p. 877-886Article in journal (Refereed)
    Abstract [en]

    The paper presents the results of studies of a total of 11 series of self-compacting concrete, which were modified with different amounts of the following nanoparticle additives: SiO2, TiO2 and Al2O3, and also a reference concrete without the addition of nanoparticles. The study included the rheological properties of concrete mixes and the physical and mechanical properties of a hardened self-compacting concrete. The characteristics of air pores obtained using a computer image analyser and analysis of a microstructure with the use of a computer microtomograph are also presented. The paper contains the results of tests of compressive strength, flexural strength, hardness and elastic modulus, which were obtained using the nanoindentation technique. The obtained results were analyzed and commented on.

  • 44.
    Orosz, Katalin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Skanska Sverige AB.
    Cwircen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Effects of variable curing temperatures on autogenous deformation of blended cement concretes2017In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 149, p. 474-480Article in journal (Refereed)
    Abstract [en]

    Shrinkage tests have been performed on blended Portland cement based early-age concrete with different w/c ratios, undergoing variable temperature curing. Results showed presence of induced non-negligible autogenous swelling which could mitigate part of the stresses related to shrinkage at very young concrete age. Recorded swelling was higher at higher curing temperatures and longer duration, especially pronounced for the low w/c mix. The swelling continued for several days after the temperature stabilized. Although not investigated directly, evidence to the nonlinear nature of the thermal expansion coefficient in young concrete has also been provided

  • 45.
    Orosz, Katalin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Humad, Abeer
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hedlund, Hans
    Skanska Sverige AB, SE-405 18 Gothenburg, Sweden.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Autogenous Deformation of Alkali-Activated Blast Furnace Slag Concrete Subjected to Variable Curing Temperatures2019In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2019, article id 6903725Article in journal (Refereed)
    Abstract [en]

    Deformations of alkali-activated slag concrete (AASC) with high MgO and Al2O3 content, subjected to variable curing temperature were studied. Sodium silicate and sodium carbonate were used as alkali activators. The obtained results showed development of deformations consisting of both shrinkage and expansion. Shrinkage appeared not to be affected by the activator type, while the expansion developed after the cooling down phase in stabilized isothermal conditions and did not stop within the duration of the tests. X-ray diffraction analysis performed shortly after the cooling down phase indicated the formation of crystalline hydrotalcite, which was associated with the observed expansion. A mixture with a higher amount of sodium silicate showed less expansion, likely due to the accelerated hydration and geopolymerization leading to the increased stiffness of the binder matrix.

  • 46.
    Rajczakowska, Magdalena
    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, Structural and Fire Engineering.
    The effect of exposure on the autogenous self-healing of Ordinary Portland cement mortarsIn: Article in journal (Refereed)
  • 47.
    Rajczakowska, Magdalena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Habermehl-Cwirzen, Karin
    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. Concrete Specialist, Skanska AB, Göteborg.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Autogenous Self-Healing: A Better Solution for Concrete2019In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 31, no 9, article id 3119001Article in journal (Refereed)
    Abstract [en]

    Self-healing can be defined as the ability of a material to repair inner damage without any external intervention. In the case of concrete, the process can be autogenous, based on optimized mix composition, or autonomous, when using additionally incorporated capsules containing a healing agent and/or bacteria spores. The first process uses unhydrated cement particles as the healing material while the other utilizes a synthetic material or bacteria released into the crack from a broken capsule or activated through access of water and oxygen. The critical reviewing of both methods indicates that the autogenous self-healing is more efficient, more cost effective, safer, and easier to implement in full-scale applications. Nevertheless, a better understanding of the mechanism and factors affecting the effectiveness of the process is needed. The main weaknesses of the autonomous method were identified as loss of workability, worsened mechanical properties, low efficiency and low probability of the healing to occur, low survivability of the capsules and bacteria in harsh concrete environment, very high price, and lack of full-scale evaluation.

  • 48.
    Rajczakowska, Magdalena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Habermehl-Cwirzen, Karin
    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. Skanska, Stockholm, Sweden.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 20, article id 3298Article in journal (Refereed)
    Abstract [en]

    It is commonly accepted that the autogenous self-healing of concrete is mainly controlled by the hydration of Portland cement and its extent depends on the availability of anhydrous particles. High-performance (HPCs) and ultra-high performance concretes (UHPCs) incorporating very high amounts of cement and having a low water-to-cement ratio reach the hydration degree of only 70–50%. Consequently, the presence of a large amount of unhydrated cement should result in excellent autogenous self-healing. The main aim of this study was to examine whether this commonly accepted hypothesis was correct. The study included tests performed on UHPC and mortars with a low water-to-cement ratio and high cement content. Additionally, aging effects were verified on 12-month-old UHPC samples. Analysis was conducted on the crack surfaces and inside of the cracks. The results strongly indicated that the formation of a dense microstructure and rapidly hydrating, freshly exposed anhydrous cement particles could significantly limit or even hinder the self-healing process. The availability of anhydrous cement appeared not to guarantee development of a highly effective healing process.

  • 49.
    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, Structural and Fire Engineering.
    Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period2019In: Nordic Concrete Research, ISSN 0800-6377, Vol. 60, no 1, p. 67-88Article in journal (Refereed)
    Abstract [en]

    This research investigates the effect of capillary pressure and the length of the hydration dormant period on the plastic shrinkage cracking tendency of SCC by studying specimens produced with different w/c ratios, cement types and SP dosages.

    The results show, that the cracking tendency of SCC was the lowest in case of w/c ratio between 0.45 and 0.55, finer rapid hardening cement and lower dosage of SP. The dormant period was prolonged by increasing the w/c ratio, using coarser cement and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure build-up rate and the length of the dormant period.

  • 50.
    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, Structural and Fire Engineering.
    Stelmarczyk, Marcin
    The Severity of Plastic Shrinkage Cracking in Concrete: A New Model2019In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763XArticle in journal (Refereed)
    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, due to evaporation is the primary cause of the phenomenon. This paper presents a new model to estimate the severity of plastic shrinkage cracking, based on the initial setting time and the amount of the evaporated water from within the concrete bulk. A number of experiments were performed under controlled ambient conditions, during which the water-cement ratio, cement type, and the dosage of superplasticizer were altered. The results, alongside those reported by other researchers, were utilized to check the validity of the proposed model. According to the outcomes, the model could predict the cracking severity of the tested concretes with a relative precision.

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