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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)
Note

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

Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-28Bibliographically 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., Habermehl-Cwirzen, K. & Cwirzen, A. (2019). Effects of fineness and chemical composition of blast furnace slag on properties of alkali-activated binder. Materials, 12(20), Article ID 3447.
Open this publication in new window or tab >>Effects of fineness and chemical composition of blast furnace slag on properties of alkali-activated binder
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 20, article id 3447Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI, 2019
Keywords
alkali-activated slag GBFS, strength, microstructure of AAS, hydration products, shrinkage
National Category
Engineering and Technology Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-76497 (URN)10.3390/ma12203447 (DOI)31640292 (PubMedID)
Funder
Luleå University of Technology, 143103
Note

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

Available from: 2019-10-24 Created: 2019-10-24 Last updated: 2019-10-28Bibliographically approved
Ghasemi, Y., Emborg, M. & Cwirzen, A. (2019). Exploring the relation between the flow of mortar and specific surface area of its constituents. Construction and Building Materials, 211, 492-501
Open this publication in new window or tab >>Exploring the relation between the flow of mortar and specific surface area of its constituents
2019 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 211, p. 492-501Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Mix design, Workability, Water demand, Particle packing theory, Excess layer theories
National Category
Building Technologies Other Civil Engineering Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73148 (URN)10.1016/j.conbuildmat.2019.03.260 (DOI)000466999500045 ()2-s2.0-85063337153 (Scopus ID)
Funder
Swedish Research Council Formas
Note

Validerad;2019;Nivå 2;2019-04-03 (svasva)

Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-06-12Bibliographically approved
Tole, I., Habermehl-Cwirzen, K. & Cwirzen, A. (2019). Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders – review. Mineralogy and Petrology, 113(4), 449-462
Open this publication in new window or tab >>Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders – review
2019 (English)In: Mineralogy and Petrology, ISSN 0930-0708, E-ISSN 1438-1168, Vol. 113, no 4, p. 449-462Article in journal (Refereed) Published
Abstract [en]

Mechanochemical activation can be defined as a process able to induce structural disorder through intensive grinding. In certain conditions, it may increase the chemical reactivity of the processed material. The process is extensively utilized in extractive metallurgy, synthesis of nanocomposites or pharmacology. It is also considered an environmentally friendly alternative to activate kaolinitic clay avoiding high calcination temperature. This paper aims to give a comprehensive overview of the process, its evolution, process parameters and applications. The paper focuses on the mechanochemical treatment of natural clay minerals, aiming at their transformation into cementitious or pozzolanic materials. It provides a summarized review of the theories related to the mechanochemistry and discusses commonly used models. The paper also analyzes various key factors and parameters controlling the mechanochemical activation process. The optimization and control of the several factors, as the filling ratio, the grinding media, the velocity, the time of grinding, etc., can promote developments and new research opportunities on different fields of application. Examples of applications, with a special focus on mechanochemically activated clay minerals and their use as cementitious binders, are listed as well.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Mechanochemistry, Grinding, Mechanochemical activation, Clay minerals, Kaolin
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73879 (URN)10.1007/s00710-019-00666-y (DOI)000475666800002 ()2-s2.0-85065650673 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-07-12 (johcin)

Available from: 2019-05-08 Created: 2019-05-08 Last updated: 2019-08-16Bibliographically approved
Tole, I., Habermehl-Cwirzen, K. & Cwirzen, A. (2019). Mechanochemically activated clay as asustainable cementitious binder. In: : . Paper presented at 2nd International Conference on Sustainable Building Materials PROCEEDINGS ICSBM 2019 (pp. 73-79). , 3
Open this publication in new window or tab >>Mechanochemically activated clay as asustainable cementitious binder
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

High-temperature requirements, emission of hazardous substances from cement kilns and the significantCO2 footprint in the calcination step are factors requiring special attention in the cement industry. Local andcommonly occurring clays can be a sustainable alternative for producing cementitious binders. Structuraldisorder in natural clay minerals can be induced through mechanochemical activation (MCA), by whichthe material develops an enhanced reactivity. The treatment of a Swedish natural clay through intensivegrinding is carried out in order to assess its potential as a sustainable cementitious binder. Several grindingparameters influence a MCA product. The filling ratio of the jar, the rotation speed, the time of grinding,as well as wet and dry environment, are variated to optimize the MCA process. The MCA process doesnot require high temperatures or added chemicals and shorter processing times can avoid high-energyrequirements during fine grinding. The structural changes of the clay were analysed by X-Ray Diffraction(XRD). Analysis of the particle size distribution of the raw and processed clay suggested a correlation withthe grinding duration. An increased ratio of grinding media versus the amount of ground material, whilelonger grinding duration increased the overall efficiency of the MCA process. The strength activity index(SAI) indicated an enhanced pozzolanic activity for the mechanochemically processed clay. Compressivestrength tests have shown a strong correlation between an enhanced amorphization rate and increasedcompressive strength values.

Keywords
alternative cementitious binders, mechanochemical activation, sustainable building materials, mechanochemistry, clay.
National Category
Engineering and Technology
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-76601 (URN)
Conference
2nd International Conference on Sustainable Building Materials PROCEEDINGS ICSBM 2019
Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04
Buasiri, T., Habermehl-Cwirzen, K., Krzeminski, L. & Cwirzen, A. (2019). Piezoresistive Load Sensing and Percolation Phenomena in Portland Cement Composite Modified with In-Situ Synthesized Carbon Nanofibers. Nanomaterials, 9(4), Article ID 594.
Open this publication in new window or tab >>Piezoresistive Load Sensing and Percolation Phenomena in Portland Cement Composite Modified with In-Situ Synthesized Carbon Nanofibers
2019 (English)In: Nanomaterials, ISSN 2079-4991, Vol. 9, no 4, article id 594Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Carbon nanofibers, CVD, percolation, piezoresistive response, compressive load
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73574 (URN)10.3390/nano9040594 (DOI)000467768800110 ()30974888 (PubMedID)2-s2.0-85065309577 (Scopus ID)
Funder
Vinnova, 2016-03285Swedish Transport Administration, TRV2017/57560
Note

Validerad;2019;Nivå 2;2019-04-15 (oliekm)

Available from: 2019-04-11 Created: 2019-04-11 Last updated: 2019-08-23Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6287-2240

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