Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 50) Show all publications
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
Ghasemi, Y., Emborg, M. & Cwirzen, A. (2019). Effect of water film thickness on flowability of conventional mortars and concretes. Materials and Structures
Open this publication in new window or tab >>Effect of water film thickness on flowability of conventional mortars and concretes
2019 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873Article in journal (Refereed) Submitted
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.

Keywords
Excess water layer theory, flow of mortar, flow of concrete, fresh cementitous mixtures
National Category
Building Technologies Other Civil Engineering
Research subject
Construction Management and Building Technology
Identifiers
urn:nbn:se:ltu:diva-73150 (URN)
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11
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)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: 2019-04-03Bibliographically 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)30974888 (PubMedID)
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: 2019-04-15Bibliographically 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
Humad, A. M., Provis, J. L. & Cwirzen, A. (2018). Alkali activation of a high MgO GGBS: fresh and hardened properties. Magazine of Concrete Research, 70(24), 1256-1264
Open this publication in new window or tab >>Alkali activation of a high MgO GGBS: fresh and hardened properties
2018 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 24, p. 1256-1264Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Westminster England: ICE Publishing, 2018
Keywords
compressive strength; curing; setting properties
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-71837 (URN)10.1680/jmacr.17.00436 (DOI)000450222300002 ()2-s2.0-85049372488 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-30 (inah)

Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2019-04-24Bibliographically approved
Bohling, D., Cwirzen, A. & Habermehl-Cwirzen, K. (2018). Bond Strength between Glass Fiber Fabrics and Low Water-to-Binder Ratio Mortar: Experimental Characterization. Advances in Civil Engineering / Hindawi, 2018, Article ID 8197039.
Open this publication in new window or tab >>Bond Strength between Glass Fiber Fabrics and Low Water-to-Binder Ratio Mortar: Experimental Characterization
2018 (English)In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, Vol. 2018, article id 8197039Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2018
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70881 (URN)10.1155/2018/8197039 (DOI)000444863000001 ()2-s2.0-85053683394 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-18 (johcin)

Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-10-03Bibliographically approved
Vehmas, T., Anna, K. & Cwirzen, A. (2018). Calcium chloride acceleration in ordinary Portland cement. Magazine of Concrete Research, 70(16), 856-863
Open this publication in new window or tab >>Calcium chloride acceleration in ordinary Portland cement
2018 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 16, p. 856-863Article in journal (Refereed) Published
Abstract [en]

Early-age hydration of ordinary Portland cement is now acknowledged to originate from nucleation and crystal growth of calcium–silicate–hydrates. The acceleration mechanism of water-soluble inorganic substances, such as calcium chloride, is still unclear. In the present study, the acceleration mechanism was approached in two independent ways. First, the acceleration effect of filler materials (limestone and quartz powder) and calcium chloride (CaCl2) were studied experimentally with a conduction calorimeter. Second, the calcium chloride effect was studied with thermodynamic modelling. The experimental test results showed that the filler materials accelerated the acceleration period of ordinary Portland cement hydration, whereas calcium chloride accelerated hydration throughout the 24 h measuring period. A synergistic effect was observed with fillers and calcium chloride. Thermodynamic modelling indicated that calcium chloride provides a supersaturation with respect to pure calcium–silicate–hydrate. It was concluded that the supersaturation provides a qualitative explanation for both calcium chloride-induced acceleration and the synergistic effect observed with fillers

Place, publisher, year, edition, pages
ICE publishing, 2018
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-68745 (URN)10.1680/jmacr.17.00079 (DOI)000438392100004 ()2-s2.0-85049945938 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-07 (rokbeg)

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-08-07Bibliographically approved
Ghasemi, Y., Mats, E. & Cwirzen, A. (2018). Estimation of specific surface area of particles based on size distribution curve. Magazine of Concrete Research, 70(10), 533-540
Open this publication in new window or tab >>Estimation of specific surface area of particles based on size distribution curve
2018 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, no 10, p. 533-540Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
London, UK: ICE PUBLISHING, 2018
Keywords
Excess water layer theory, Aggregate shape, Workability, Fresh concrete
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65668 (URN)10.1680/jmacr.17.00045 (DOI)000430044700005 ()2-s2.0-85045533136 (Scopus ID)
Projects
Concrete mix design development
Funder
Swedish Research Council
Note

Validerad;2018;Nivå 2;2018-04-16 (rokbeg)

Available from: 2017-09-15 Created: 2017-09-15 Last updated: 2019-03-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6287-2240

Search in DiVA

Show all publications