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Flowability and proportioning of cementitious mixtures
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0003-2567-5891
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Flytbarhet och proportionering avcementblandnigar (Swedish)
Abstract [en]

Understanding the role of constituents of cementitious mixtures as the most globally used human-made material and their effect on the flowability of the blends is of great importance. A comprehensive understanding of the ingredients of mixtures allows for optimized proportioning of constituents and can lead to a reduction in cement and water demand of the blends.

The thesis focuses on relating the flow of mixtures to the specific surface area of the particles through the concepts of excess water layer theory by assuming that the particles are enveloped by a thin film layer that separates the grains and lubricates their surfaces. However, in order to study the film thickness, it is inevitable to consider packing density and specific surface area of the particles. Both of the mentioned parameters and their influence on water requirement of mixtures were investigated as a part of the project.

The theoretical part of the thesis includes background and explanation of the concepts and theories used in conducting the research including particle packing theory, specific surface area, and excess layer theories. In addition, the thesis attempts at defining and formulating terms and parameters such as representative shape, mixer efficiency, and optimal packing.

The experimental part of the thesis consists of laboratory measurements of packing density in the loose state, estimation of specific surface area using microtomography and slump tests for mortar and concrete.

The results of the thesis indicate that the available packing models can estimate the packing density with acceptable accuracy. In addition, it was shown that it is possible to estimate flowability of mixtures based on information about the specific surface area of the constituents. A mix design approach is introduced which predicts flow spread of slump test, a measure that is often used in laboratories and at the building sites.

Moreover, the research revealed that the estimation of the specific surface area of particles can be improved by assuming a platonic solid shape for the particles instead of spheres. Furthermore, the mixer efficiency was quantified and optimization of mixtures against packing density and water requirement was explained.

The finding of the project lays a foundation for a simple workability based mix design approach.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords [en]
Particle packing, excess layer theory, mix design
National Category
Other Civil Engineering Building Technologies
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-73152ISBN: 978-91-7790-328-4 (print)ISBN: 978-91-7790-329-1 (electronic)OAI: oai:DiVA.org:ltu-73152DiVA, id: diva2:1295176
Public defence
2019-05-03, F1031, Lulea, 10:30 (English)
Opponent
Supervisors
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-04-30Bibliographically approved
List of papers
1. Particle Packing for Concrete Mix Design: Models vs. Reality
Open this publication in new window or tab >>Particle Packing for Concrete Mix Design: Models vs. Reality
2014 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 85-94Article in journal (Refereed) Published
Abstract [en]

The packing density of aggregates is of great importance in concrete mix design as obtaining a higher packing density leads to less usage of cement paste which has technical, environmental and economic benefits. It is thus of interest to model particle packing correctly. Hence, in this study, packing densities of seven mixes of aggregate were attained in the laboratory using the loose packing method and were compared to values suggested by three models: 4C, Compressible Packing Model and Modified Toufar Model. Modified Toufar showed 1.72% mean difference from the laboratory values while CPM and 4C had mean differences of 1.79% and 1.84% respectively. In addition, it was found that some of the models are preferable in certain mixtures.

Keywords
Materials science - Construction materials, Civil engineering and architecture - Building engineering, Teknisk materialvetenskap - Konstruktionsmaterial, Samhällsbyggnadsteknik och arkitektur - Byggnadsteknik
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-11550 (URN)a8da796a-d226-4f81-bf32-6533318afb9e (Local ID)a8da796a-d226-4f81-bf32-6533318afb9e (Archive number)a8da796a-d226-4f81-bf32-6533318afb9e (OAI)
Note
Validerad; 2014; 20141209 (yahgha)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-03-11Bibliographically approved
2. Estimation of specific surface area of particles based on size distribution curve
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
3. Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography
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)
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: 2019-12-16Bibliographically approved
4. Exploring the relation between the flow of mortar and specific surface area of its constituents
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
5. Effect of water film thickness on the flow in conventional mortars and concrete
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
6. A theoretical study on optimal packing in mortar and paste
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

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