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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
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
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
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
Ghasemi, Y., Rajczakowska, M., Emborg, M. & Cwirzen, A. (2018). Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography. Magazine of Concrete Research
Open this publication in new window or tab >>Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography
2018 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763XArticle in journal (Refereed) Epub ahead of print
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, 2018
Keywords
Mix design, Water film thickness, Excess water layer theory, specific surface area, aggregates, testing, apparatus & methods, workability
National Category
Other Civil Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-71374 (URN)10.1680/jmacr.18.00121 (DOI)
Funder
Swedish Research Council Formas
Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2019-08-16
Ghasemi, Y. & Emborg, M. (2017). A method for obtaining optimum packing of aggregates for concrete at the onset of flow. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017 (pp. 361-365). Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>A method for obtaining optimum packing of aggregates for concrete at the onset of flow
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017, p. 361-365Conference paper, Published paper (Refereed)
Abstract [en]

Particle packing models have been studied extensively during past decades and led to development of some complex and relatively accurate predictions of packing of granular materials. While the models are capable of calculating the packing density for different volumetric share of constitutes, the concept of optimum packing remains unclear. The study aims to define optimum packing based on particle packing theory and excess water layer theory .The approach makes it also possible to calculate amount of paste that is required to put a concrete mixture at the onset of flow. Some pilot tests conducted in the laboratory showed good agreement with calculated data.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
Keywords
Excess layer theory, Optimum packing, Specific surface area, Zero-slump
National Category
Building Technologies Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65692 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Projects
Concrete mix design
Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2018-04-03Bibliographically approved
Sayahi, F., Emborg, M. & Hedlund, H. (2017). Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017. Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Plastic shrinkage cracking is a mechanical phenomenon that occurs in the first few hours after casting the concrete in its mould. It is commonly believed that rapid and excessive moisture loss of the fresh concrete, mainly due to evaporation, plays a decisive role in the early age shrinkage. However, it is not always possible to justify all the plastic shrinkage incidents based on water evaporation solely. Instead, it seems that and interconnected correlation between evaporation, capillary pressure and hydration rate may offer better explanation. In this paper effect of water-cement (w/c) ratio on plastic shrinkage cracking of self-compacting concrete (SCC) is investigates. Four recipes with different w/c ratios (0.38, 0.45, 0.55 and 0.67) are tested by using Ring test method (NT BUILD 433). During the experiments evaporation, capillary pressure and internal temperature of the specimens were recorded from 60 minutes after casting up to 18 hours, at which the length and width of the cracks were measured. The results show lower risk of cracking when w/c ratio is between 0.45 to 0.55. However, the specimens with 0.38 and 0.67 w/c ratio experienced higher cracking tendency, especially the latter, in which severe cracking was observed.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65992 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-28Bibliographically approved
Persson, M., Ohlsson, U., Silfwerbrand, J. & Emborg, M. (2017). Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017. Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>Interface stresses in concrete bridge deck overlays subjected to differentialshrinkage
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Concrete overlays on bridge decks are expected to be more durable as compared with the more common asphalt solution. Besides stresses due to traffic load and temperature variations at service, the overlays are exposed to stresses due to long term shrinkage. Of interest is to evaluate the concrete overlay due to the shrinkage induced stresses at the composite interface. Three strategies have been employed to gain knowledge on the stresses; 1) use of non-destructive test systems via field observations, 2) a numerical study on a concrete composite slab tested in laboratory, 3) recordings of realistic shrinkage and climate data on a reference bridge using vibrating strain gauges and humidity probes in the newly cast concrete overlay. The data were used as input data for a linear elastic finite element model. This article demonstrates this last phase of the work.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65991 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-27Bibliographically approved
Sayahi, F., Emborg, M. & Hedlund, H. (2017). Plastic Shrinkage Cracking in Concrete: Influence of Test Methods. In: : . Paper presented at 2nd International RILEM/COST Conference on Early Age Cracking and Serviceability in Cement-based Materials and Structures - EAC2, Brussels, Belgium, 12–14 September 2017.
Open this publication in new window or tab >>Plastic Shrinkage Cracking in Concrete: Influence of Test Methods
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Plastic shrinkage cracking can become problematic especially in concrete elements with high surface to volume ratio such as slabs and pavements. In this paper two test methods commonly used when studying the phenomenon have been evaluated; ring test method (NORDTEST-method NT Build 433) developed in NTNU/SINTEF by Johansen and Dahl in order to study the effect of different materials and constituents on the cracking tendency at macro-level, and ASTM C 1579, mainly designed in order to map the influence of fibres. During this research, influence of coarse aggregate content on plastic shrinkage cracking of self-compacting concrete (SCC) was studied. Preliminary results show same tendencies with the two methods i.e. a lower plastic shrinkage tendency with higher amount of coarse aggregates.

National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65993 (URN)
Conference
2nd International RILEM/COST Conference on Early Age Cracking and Serviceability in Cement-based Materials and Structures - EAC2, Brussels, Belgium, 12–14 September 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-03-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3997-3083

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