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Publications (10 of 66) Show all publications
Tole, I., Rajczakowska, M., Humad, A., Kothari, A. & Cwirzen, A. (2020). Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag. Materials, 13(5), Article ID 1134.
Open this publication in new window or tab >>Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag
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2020 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 13, no 5, article id 1134Article in journal (Refereed) Published
Abstract [en]

An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
mechanochemistry, alkali activation, air-cooled slag, ground granulated slag, mechanical activation, cement-free mortars
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-78303 (URN)10.3390/ma13051134 (DOI)32143319 (PubMedID)2-s2.0-85081681477 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-04-02 (alebob)

Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
Sayahi, F., Emborg, M., Hedlund, H., Cwirzen, A. & Stelmarczyk, M. (2020). Modelling the Severity of Plastic Shrinkage in Cementitious Materials. In: Proceedings of the international Conference on Civil Infrastructure of Construction (CUSC 2020): . Paper presented at International Conference on Civil Infrastructure and Construction (CIC 2020), 2-5 Febuary, 2020, Doha, Qatar (pp. 566-573). Qatar University Press
Open this publication in new window or tab >>Modelling the Severity of Plastic Shrinkage in Cementitious Materials
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2020 (English)In: Proceedings of the international Conference on Civil Infrastructure of Construction (CUSC 2020), Qatar University Press , 2020, p. 566-573Conference paper, Published paper (Other academic)
Abstract [en]

Plastic shrinkage cracking in cement-based materials occurs between the mixing and the final setting of the mixture, where rapid evaporation of the mixed water is the main cause behind the phenomenon. The induced cracks may impair the durability and sustainability of the structure by facilitating ingress of harmful materials into the concrete bulk. In this paper a new model for estimating the cracking severity of plastic cementitious materials is presented based on the mixture’s initial setting time and the amount of the pore liquid evaporated from within the concrete mass. Results of experiments performed by the authors in another study, in addition to results of tests performed by other researchers are used to control the validity of the model. It is concluded that the model can anticipate the cracking severity of plastic concretes with good precision. The new method can provide practical tools for designers and contractors to predict and compare the cracking risk of the concretes prior to casting.

Place, publisher, year, edition, pages
Qatar University Press, 2020
Keywords
Plastic shrinkage cracking, Initial setting, Evaporation, Bleeding, Modelling
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-78794 (URN)10.29117/cic.2020.0071 (DOI)
Conference
International Conference on Civil Infrastructure and Construction (CIC 2020), 2-5 Febuary, 2020, Doha, Qatar
Available from: 2020-05-05 Created: 2020-05-05 Last updated: 2020-05-18Bibliographically approved
Cwirzen, A. (2020). Properties of SCC with industrial by-products as aggregates. In: Rafat Siddique (Ed.), Self-Compacting Concrete: Materials, Properties, and Applications (pp. 249-281). Woodhead Publishing Limited
Open this publication in new window or tab >>Properties of SCC with industrial by-products as aggregates
2020 (English)In: Self-Compacting Concrete: Materials, Properties, and Applications / [ed] Rafat Siddique, Woodhead Publishing Limited, 2020, p. 249-281Chapter in book (Other academic)
Abstract [en]

Concrete contains up to 80 volume percentage of aggregates which forces producers to use extensively available local resources to avoid very high transportation costs and related carbon dioxide emissions. In addition, many regions around the world face increasing problems to obtain good quality natural aggregates and the only alternative is to use various types of wastes, industrial by products or recycled concrete. If application of these types of aggregates in normal concretes is rather common, the situation is quite different in the case of the self-compacting concrete.

This chapter will focus on reviewing current Stata of the art on utilization of aggregates produced from wastes and industrial by products. A number of currently available waste streams are described and their potential for application in self-compacting concrete is evaluated. Effects on fresh and hardened concrete properties are described. In addition, basic physical properties and durability aspects are addressed as well.

Place, publisher, year, edition, pages
Woodhead Publishing Limited, 2020
Series
Woodhead Publishing Series in Civil and Structural Engineering
Keywords
Aggregates, Industrial waste, Communal waste, Strength, Durability
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-78655 (URN)10.1016/B978-0-12-817369-5.00010-6 (DOI)
Note

ISBN för värdpublikation: 978-0-12-817369-5

Available from: 2020-04-24 Created: 2020-04-24 Last updated: 2020-04-24Bibliographically approved
Ghasemi, Y., Rajczakowska, M., Emborg, M. & Cwirzen, A. (2020). Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography. Magazine of Concrete Research, 72(2), 88-96
Open this publication in new window or tab >>Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography
2020 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 72, no 2, p. 88-96Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ICE publishing, 2020
Keywords
Mix design, Water film thickness, Excess water layer theory, specific surface area, aggregates, testing, apparatus & methods, workability
National Category
Infrastructure Engineering Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-71374 (URN)10.1680/jmacr.18.00121 (DOI)000502339000003 ()
Funder
Swedish Research Council Formas
Note

Validerad;2020;Nivå 2;2019-12-16 (johcin)

Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2020-02-25Bibliographically approved
Ghasemi, Y., Emborg, M. & Cwirzen, A. (2019). A theoretical study on optimal packing in mortar and paste. Advances in Cement Research
Open this publication in new window or tab >>A theoretical study on optimal packing in mortar and paste
2019 (English)In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605Article in journal (Refereed) Submitted
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. 

Keywords
Excess layer theory, packing density, optimal packing
National Category
Building Technologies Other Civil Engineering
Identifiers
urn:nbn:se:ltu:diva-73151 (URN)
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11
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
Rajczakowska, M., Habermehl-Cwirzen, K., Hedlund, H. & Cwirzen, A. (2019). Autogenous Self-Healing: A Better Solution for Concrete. Journal of materials in civil engineering, 31(9), Article ID 3119001.
Open this publication in new window or tab >>Autogenous Self-Healing: A Better Solution for Concrete
2019 (English)In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 31, no 9, article id 3119001Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2019
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-75206 (URN)10.1061/(ASCE)MT.1943-5533.0002764 (DOI)000475694700023 ()2-s2.0-85067520596 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-07-03 (svasva)

Available from: 2019-07-03 Created: 2019-07-03 Last updated: 2019-10-28Bibliographically approved
Rajczakowska, M., Nilsson, L., Habermehl-Cwirzen, K., Hedlund, H. & Cwirzen, A. (2019). Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?. Materials, 12(20), Article ID 3298.
Open this publication in new window or tab >>Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 20, article id 3298Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
continued hydration, ultra-high performance concrete, cracking, microstructure, calcite
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-76510 (URN)10.3390/ma12203298 (DOI)000498402100021 ()
Note

Validerad;2019;Nivå 2;2019-10-28 (johcin)

Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-12-18Bibliographically approved
Ghasemi, Y., Emborg, M. & Cwirzen, A. (2019). Effect of water film thickness on the flow in conventional mortars and concrete. Materials and Structures, 52(3), Article ID 62.
Open this publication in new window or tab >>Effect of water film thickness on the flow in conventional mortars and concrete
2019 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 3, article id 62Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Excess water layer theory, flow of mortar, flow of concrete, fresh cementitous mixtures
National Category
Other Civil Engineering Other Materials Engineering
Research subject
Building Materials; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-73150 (URN)10.1617/s11527-019-1362-9 (DOI)000469403900001 ()2-s2.0-85066505381 (Scopus ID)
Funder
Swedish Research Council Formas
Note

Validerad;2019;Nivå 2;2019-06-20 (johcin)

Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-06-20Bibliographically approved
Humad, A., Provis, J. L. & Cwirzen, A. (2019). Effects of Curing Conditions on Shrinkage of Alkali-Activated High-MgO Swedish Slag Concrete. FRONTIERS IN MATERIALS, 6, Article ID 287.
Open this publication in new window or tab >>Effects of Curing Conditions on Shrinkage of Alkali-Activated High-MgO Swedish Slag Concrete
2019 (English)In: FRONTIERS IN MATERIALS, ISSN 2296-8016, Vol. 6, article id 287Article in journal (Refereed) Published
Abstract [en]

This study aimed to determine the effects of curing regime on shrinkage of alkali-activated concretes produced from a Swedish high-MgO blast furnace slag. Sodium carbonate (SC), sodium silicate (SS), and their combination were used as alkali activators. The studied curing procedure included heat-treatment, no heat-treatment, sealed and non-sealed conditions. The heat curing increased the compressive strengths of the concretes activated with SS and with the combination of SS and SC. Sealed-curing applied for a period of 1 month reduced the measured drying shrinkage by up to 50% for all studied heat-treated samples. Conversely, the same curing procedure significantly increased the development of the drying shrinkage once the seal was removed after 28 days of curing in the case of the SC-activated concretes non-heat treated. Higher degree of reaction/hydration reached by the binders in these concretes was indicated as the main factor. All of the concretes studied had showed a significant microcracking of the binder matrix, with the most extensive cracking observed in the sealed lab-cured mixes. The heat-cured mixes activated with SS and combination of SC and SS showed the most homogenous microstructure and low extensive micro cracking comparing with lab-cured ones.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-77237 (URN)10.3389/fmats.2019.00287 (DOI)000500776400001 ()
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2020-03-31Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6287-2240

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