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Orosz, K., Humad, A., Hedlund, H. & Cwirzen, A. (2019). Autogenous Deformation of Alkali-Activated Blast Furnace Slag Concrete Subjected to Variable Curing Temperatures. Advances in Civil Engineering / Hindawi, 2019, Article ID 6903725.
Open this publication in new window or tab >>Autogenous Deformation of Alkali-Activated Blast Furnace Slag Concrete Subjected to Variable Curing Temperatures
2019 (English)In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2019, article id 6903725Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2019
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-74369 (URN)10.1155/2019/6903725 (DOI)000473368400001 ()2-s2.0-85066020513 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-26 (johcin)

Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2019-08-16Bibliographically approved
Orosz, K. (2017). Early age autogenous deformation and cracking of cementitious materials – Implications on strengthening of concrete. (Doctoral dissertation). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Early age autogenous deformation and cracking of cementitious materials – Implications on strengthening of concrete
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2017
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
concrete, mortar, strengthening, composites, shrinkage, autogenous deformation, alkali activated materials, alkali activated slag
National Category
Other Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63337 (URN)978-91-7583-908-0 (ISBN)978-91-7583-909-7 (ISBN)
Public defence
2017-06-19, F1031, Luleå tekninska universitet, Luleå, 13:00 (English)
Opponent
Supervisors
Funder
SBUF - Sveriges Byggindustriers UtvecklingsfondSwedish Transport Administration
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2017-11-24Bibliographically approved
Orosz, K., Hedlund, H. & Cwircen, A. (2017). Effects of variable curing temperatures on autogenous deformation of blended cement concretes. Construction and Building Materials, 149, 474-480
Open this publication in new window or tab >>Effects of variable curing temperatures on autogenous deformation of blended cement concretes
2017 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 149, p. 474-480Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63597 (URN)10.1016/j.conbuildmat.2017.05.143 (DOI)000405536800044 ()2-s2.0-85019772715 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-05-29 (andbra)

Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2018-07-10Bibliographically approved
Orosz, K., Fjellström, P., Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Evaluation of the Linear Logarithmic Creep Model (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 417-420
Open this publication in new window or tab >>Evaluation of the Linear Logarithmic Creep Model
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2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 417-420Article in journal (Refereed) Published
Abstract [en]

In order to make reliable predictions of thermal cracking risks in young concrete, modelling of the creep behaviour is important. The linear logarithmic creep model (LLM) has only been used to describe the creep behaviour of moisture-sealed concrete samples (basic creep). The aim of the present research is to check whether LLM could be also applied to drying creep. The results indicate that the LLM delivers good results for sealed but not for drying samples. Thus, refinement of the existing model (e.g., tri-linear instead of bi-linear in logarithmic time scale), or a new model is needed to account for the increase of creep due to on-going drying.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-28345 (URN)21e99458-34c1-4122-8238-0b6afbf87fe3 (Local ID)21e99458-34c1-4122-8238-0b6afbf87fe3 (Archive number)21e99458-34c1-4122-8238-0b6afbf87fe3 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140829 (katoro); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-25Bibliographically approved
Orosz, K., Fjellström, P., Jonasson, J.-E., Emborg, M. & Hedlund, H. (2014). Evaluation of Thermal Dilation and Autogenous Shrinkage at Sealed Conditions (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 299-302
Open this publication in new window or tab >>Evaluation of Thermal Dilation and Autogenous Shrinkage at Sealed Conditions
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2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 299-302Article in journal (Refereed) Published
Abstract [en]

As known, load independent deformations are of large importance in structural analysis, e. g. when estimating elongations, restraint stresses, or pre-stressing forces. Two models to describe thermal dilation (TD) and autogenous shrinkage (AS) have been evaluated, for a broader range of w/C ratios and cements types than before. In Model I, AS is determined solely based on the maturity model and TD incorporates two TD coefficients (TDC). In Model II, AS is dependent on both the maturity model and a separate temperature adjustment factor, while TDC is constant. For the more rapid-hardening cement, Model I did not give satisfactory results, whereas the usefulness of Model II to describe both AS and TD has shown to be limited, suggesting that a new model is needed.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-31101 (URN)529e1b20-d576-493d-8f5d-c5c22c0395de (Local ID)529e1b20-d576-493d-8f5d-c5c22c0395de (Archive number)529e1b20-d576-493d-8f5d-c5c22c0395de (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140829 (katoro); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-25Bibliographically approved
Orosz, K. (2014). Strengthening of Concrete with Carbon Fibre Reinforced Polymer (CFRP) Grids Bonded by Cementitious Binders (ed.). Paper presented at Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014. Nordic Concrete Research, 50, 207-210
Open this publication in new window or tab >>Strengthening of Concrete with Carbon Fibre Reinforced Polymer (CFRP) Grids Bonded by Cementitious Binders
2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 207-210Article in journal (Refereed) Published
Abstract [en]

Knowledge of the tensile behaviour of the strengthening material is important to estimate the shear capacity of the strengthened structure. In this paper, the tensile behaviour of externally bonded carbon fibre polymer (CFRP) grids has been studied. Bonding agent was either quasi-brittle polymer-modified mortar (PMM) or strain-hardening (“ductile”) mortar, instead of the typical epoxy resin. Uniaxial tensile and wedge-splitting tests were conducted to investigate the tensile-, and post-cracking behaviour, toughness, and ductility. The strain-hardening mortar enhanced both the load bearing- and in particular, the deformation capacity, surpassing the benefits of the PMM. The “ductile” mortar has also shifted the overall behaviour from brittle towards a more ductile failure.Keywords: Concrete, Strengthening, CFRP, Testing, Strain Hardening, Tensile Behaviour, Cracking, Brittleness, Deformation Capacity

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-38575 (URN)d038cb4b-b674-4d3e-b453-55f92691e3c6 (Local ID)d038cb4b-b674-4d3e-b453-55f92691e3c6 (Archive number)d038cb4b-b674-4d3e-b453-55f92691e3c6 (OAI)
Conference
Nordic Concrete Research Symposia : 13/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140829 (katoro); Konferensartikel i tidskriftAvailable from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-05-25Bibliographically approved
Orosz, K., Blanksvärd, T., Täljsten, B. & Fischer, G. (2013). Crack development and deformation behaviour of CFRP-reinforced mortars (ed.). Paper presented at . Nordic Concrete Research, 48, 49-69
Open this publication in new window or tab >>Crack development and deformation behaviour of CFRP-reinforced mortars
2013 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 48, p. 49-69Article in journal (Refereed) Published
Abstract [en]

This paper reports on a research study investigating CFRPreinforced mortars in uniaxial tension, as a strengthening material for concrete structures. The bare strengthening material was tested on dogbone specimens. Crack formation, crack development and the interaction between the grid and the mortar phase with varying geometrical parameters and mortar compositions have been investigated and evaluated. The use of engineered cementitious composites, exhibiting multiple cracking and enhanced pseudo-ductility in uniaxial tension, was found to result in an improved overall performance.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-15091 (URN)e8e77786-c4b1-4bfb-bb6d-57d675e53f59 (Local ID)e8e77786-c4b1-4bfb-bb6d-57d675e53f59 (Archive number)e8e77786-c4b1-4bfb-bb6d-57d675e53f59 (OAI)
Note
Validerad; 2013; 20131216 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-25Bibliographically approved
Orosz, K. (2013). Tensile behaviour of mineral-based composites (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Tensile behaviour of mineral-based composites
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Externally bonded fibre-reinforced polymer (FRP) systems have shown to be a robust and durable way to repair, or strengthen concrete structures. Epoxy, as the most common bonding agent, provides excellent force transfer, and bonds well to the base substrate to the as well as to the strengthening material. However, the epoxy-bonded systems exhibit certain inherent weaknesses, such as low compatibility with the concrete substrate, degradation in strength and stiffness around 85 °C, and toxicity both during application and when subjected to fire. Epoxies also require a minimum application temperature often above 10 °C, and create sealed surfaces, potentially resulting in moisture and freeze/thaw problems.In recent years, alternative, inorganic bonding agents have been in the focus of research. Cementitious bonding agents, when combined with the FRP, have the potential to become a high-performance strengthening system, without the drawbacks of the epoxy-bonded systems. Inorganic binders provide excellent protection to the FRP against UV-degradation, fire, or vandalism. Contrary to epoxy, they can be applied in colder temperatures or climates. They show a better compatibility with the base concrete in terms of chemical or thermal compatibility, shrinkage properties, and they do not create diffusion-closed surfaces.In this thesis, the mineral-based composite (MBC) strengthening system has been investigated, with focus on the tensile behaviour of the material. The MBC comprises of a carbon fibre polymer (CFRP) grid and an inorganic, mineral-based binder. Additionally, MBC has been placed in a wider context within the field of externally bonded, mineral-based strengthening systems. On the material side, MBC has been modified and enhanced by involving strain-hardening mortars. The experimental work presented in the thesis consists of two test series aiming to investigate the tensile behaviour. First, uniaxial tensile tests were carried out on dogbone-shaped specimens, to characterize the tensile properties of the bare composite strengthening material. Then, wedge-splitting tests were conducted to investigate the post-cracking behaviour, toughness, and ductility of the MBC, and the interaction between the MBC and the base concrete.The chosen test methods have proven to be suitable to characterize the tensile behaviour of the MBC. In all cases, the specimens failed with CFRP rupture, indicating good bond, both on the base concrete-mortar, and the mortar-CFRP interface. The MBC strengthening system performed excellent in terms of load-carrying capacity. Furthermore, the strain-hardening mortar has been found to enhance both the load bearing and in particular, the deformation capacity. It has also been shown that the pseudo-ductile mortar is capable to shift the overall behaviour from brittle towards a more ductile failure.The potential in such improved mineral-based strengthening systems is enormous. The ductility provided by the strain-hardening mortars together with the stiffness and strength from the FRP component could result in a high-performance strengthening material applicable in a range of different situations, from shear-sensitive structures through mining applications, such as tunnel linings.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-17404 (URN)34479c60-ca1e-43f0-876e-f8b7038316d0 (Local ID)978-91-7439-662-1 (ISBN)978-91-7439-663-8 (ISBN)34479c60-ca1e-43f0-876e-f8b7038316d0 (Archive number)34479c60-ca1e-43f0-876e-f8b7038316d0 (OAI)
Note
Godkänd; 2013; 20130514 (katoro); Tillkännagivande licentiatseminarium 2013-05-29 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Katalin Orosz Ämne: Konstruktionsteknik/Structural Engineering Uppsats: Tensile Behaviour of Mineral-Based Composites Examinator: Professor Mats Emborg, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Docent, Vice head of dept., Head of division Anders Ansell, KTH, Division of Concrete Structures, Stockholm Tid: Fredag den 14 juni 2013 kl 13.00 Plats: F1031, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-25Bibliographically approved
Orosz, K., Blanksvärd, T., Täljsten, B. & Fischer, G. (2010). From material level to structural use of mineral-based composites: An overview (ed.). Advances in Civil Engineering / Hindawi, 2010, Article ID 985843.
Open this publication in new window or tab >>From material level to structural use of mineral-based composites: An overview
2010 (English)In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2010, article id 985843Article in journal (Refereed) Published
Abstract [en]

This paper surveys different material combinations and applications in the field of mineral-based strengthening of concrete structures. Focus is placed on mechanical behaviour on material and component levels in different cementitious composites; with the intention of systematically maping the applicable materials and material combinations for mineral-based strengthening. A comprehensive description of a particular strengthening system developed in Sweden and Denmark, denominated as Mineral-based Composites (MBCs), together with tests from composite material properties to structural elements is given. From tests and survey it can be concluded that the use of mineral-based strengthening system can be effectively used to increase the load bearing capacity of the strengthened structure. The paper concludes with suggestions on further development in the field of mineral-based strengthening

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-3960 (URN)10.1155/2010/985843 (DOI)2-s2.0-79958176968 (Scopus ID)1ce764b6-7481-46c4-80db-077ffca7afcc (Local ID)1ce764b6-7481-46c4-80db-077ffca7afcc (Archive number)1ce764b6-7481-46c4-80db-077ffca7afcc (OAI)
Note

Validerad; 2011; 20110622 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Täljsten, B., Orosz, K. & Blanksvärd, T. (2006). Strengthening of concrete beams in shear with mineral based composites: laboratory tests and theory (ed.). In: (Ed.), (Ed.), International Conference on FRP Composites in Civil Engineering: CICE 2006. Paper presented at International Conference on FRP Composites in Civil Engineering : 13/12/2006 - 15/12/2006.
Open this publication in new window or tab >>Strengthening of concrete beams in shear with mineral based composites: laboratory tests and theory
2006 (English)In: International Conference on FRP Composites in Civil Engineering: CICE 2006, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Today, there are many different repair and strengthening methods that might be used to upgrade a concrete structure. One such method involves CFRP (Carbon Fibre Reinforced Polymer) bonding. This method has proven to be usable for many different types of retrofitting applications. Even so, there are some disadvantages while using epoxy resins as a bonding agent, i.e. diffusion closeness, thermal compatibility, working environment and the minimum temperature of assemble. It is therefore of interest to replace the epoxy adhesive with a mineral based bonding agent, e.g. polymer modified mortars with similar properties as the base concrete that also is more working environmental friendly. A combination between the polymer modified mortar and fibre reinforced polymers (FRP) can be used for repair and strengthening of civil structures. This paper presents a pilot study of RC beams strengthened in shear with mineral based bonding agents and CFRP grids. The project is a collaboration project among Luleå University of Technology, Norut Teknologi AS and Denmark Technical University and is also a part of the European funded project "Sustainable Bridges". The results so far show that comparable strengthening results as for epoxy bonded systems can be achieved with MBC strengthening systems. The strengthening effect of the beams was 40 - 100 % compared to the unstrengthened reference beam. The theoretical model describes the load carrying capacity fairly well.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-34482 (URN)8b19f320-be01-11db-9be7-000ea68e967b (Local ID)8b19f320-be01-11db-9be7-000ea68e967b (Archive number)8b19f320-be01-11db-9be7-000ea68e967b (OAI)
Conference
International Conference on FRP Composites in Civil Engineering : 13/12/2006 - 15/12/2006
Note
Godkänd; 2006; 20070207 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2922-5815

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