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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: 2019-08-16Bibliographically 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
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
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
Sayahi, F., Emborg, M., Hedlund, H. & Cwirzen, A. (2019). Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period. Nordic Concrete Research, 60(1), 67-88
Open this publication in new window or tab >>Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period
2019 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 60, no 1, p. 67-88Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Norsk betongförening, 2019
Keywords
plastic shrinkage, cracking, evaporation, capillary pressure, dormant period, self-compacting concrete.
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73170 (URN)10.2478/ncr-2019-0012 (DOI)000475508100006 ()
Note

Validerad;2019;Nivå 2;2019-07-23 (svasva)

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-08-16Bibliographically approved
Humad, A., Kothari, A., Provis, J. L. & Cwirzen, A. (2019). The Effect of Blast Furnace Slag/Fly Ash Ratio on Setting, Strength, and Shrinkage of Alkali-Activated Pastes and Concretes. Frontiers in Materials, 6(9)
Open this publication in new window or tab >>The Effect of Blast Furnace Slag/Fly Ash Ratio on Setting, Strength, and Shrinkage of Alkali-Activated Pastes and Concretes
2019 (English)In: Frontiers in Materials, ISSN 2296-8016, Vol. 6, no 9Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
fly ash FA, blast furnace slag BFS, initial and final setting time, shrinkage, alkali-activated binders
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-73145 (URN)10.3389/fmats.2019.00009 (DOI)000458669200001 ()2-s2.0-85062450166 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-08 (johcin)

Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-03-15Bibliographically approved
Tole, I., Habermehl-Cwirzen, K., Rajczakowska, M. & Cwirzen, A. (2018). Activation of a Raw Clay by Mechanochemical Process: Effects of Various Parameters on the Process Efficiency and Cementitious Properties. Materials, 11(10), Article ID 1860.
Open this publication in new window or tab >>Activation of a Raw Clay by Mechanochemical Process: Effects of Various Parameters on the Process Efficiency and Cementitious Properties
2018 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, no 10, article id 1860Article in journal (Refereed) Published
Abstract [en]

The efficiency of the mechanochemical activation (MCA) is influenced by various process parameters as well as by the properties of the treated material. The main objective of this research was to optimize the MCA process, gaining enhancement of the chemical reactivity of a Swedish raw clay, which is going to be used as an alkali-activated cementitious binder. The effects of the amount of water, the filling ratio, the rotation speed, and the grinding duration on the amorphization degree were evaluated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Generally, wet and dry processes showed an extensive amorphization of both kaolinite and muscovite minerals present in the studied clay. On the contrary, quartz was amorphized mainly by the wet grinding process. The efficiency of both dry and wet grinding processes was enhanced by the increased number of grinding media versus the amount of the activated material. However, longer processing times caused significant agglomeration while a higher rotational speed enhanced the amorphization. Preliminary tests have shown that alkali activation of the processed clays produced hardened samples. Furthermore, the increased amorphization corresponded to the increased compressive strength values.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
clay minerals, dry grinding, fine grinding, mechanochemical activation, mechanochemistry, wet grinding
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-71035 (URN)10.3390/ma11101860 (DOI)30274273 (PubMedID)2-s2.0-85054276282 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-03 (marisr)

Available from: 2018-09-30 Created: 2018-09-30 Last updated: 2019-04-02Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6287-2240

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