Metakaolin and Fly Ash as Mineral Admixtures for Concrete

241 Pages·2021·16.385 MB·English

by  Leonid Dvorkin, Vadim Zhitkovsky, Nataliya Lushnikova, Yuri Ribakov

Metakaolin and Fly Ash
as Mineral Admixtures
for Concrete
Leonid Dvorkin
Professor and Head Department of Building Products Technology
and Material Science National University of Water and Environmental Engineering
Rivne, Ukraine
Vadim Zhitkovsky
National University of Water and Environmental Engineering
Rivne, Ukraine
Nataliya Lushnikova
National University of Water and Environmental Engineering
Rivne, Ukraine
Yuri Ribakov
Ariel University, Israel
p,
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A SCIENCE PUBLISHERS BOOK
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First edition published 2021
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DOI : 10.1201/ 9781003096825
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Preface

The use of mineral admixtures in cement concrete began in the second half of the
nineteenth century with the beginning of its massive use in construction. Initially,
based on experience of ancient Greeks and Romans volcanic rocks were used to
obtain water—resistant mortars. These and other lime-active admixtures began to
be used for increasing cement concrete water and corrosion resistance, especially
in sea water, and then to modify their properties and save Portland cement.
Active mineral admixtures have acquired particular importance in technology of
new generation concretes, characterized by a number of improved construction
and technical properties. Using such a highly active mineral admixture as
microsilica in a composition with superplasticizers made it possible to radically
improve concrete technological, strength and deformative properties as well as
its durability. At the same time, production abilities for obtaining microsilica are
limited, and there are difficulties with its transportation and dosing. Therefore
it is logical to use it in modern concrete in a composition with admixtures of
superplasticizers and other more easily available and cheap mineral admixtures,
like fly ash and metakaolin.
The monograph presents results of experimental studies carried out by the
authors to investigate the formation of the main properties of high-strength,
reaction-powder, self-compacting and self-leveling concrete with complex
admixtures, including fly ash, metakaolin and their compositions. Structure
formation features and experimental statistical models are analyzed to quantify
the influence of the main technological factors on the properties of concrete
mixtures and hardened concrete. A methodology for the design of concrete
compositions with organic mineral modifiers, including superplasticizers, fly ash
and metakaolin is proposed.
The authors hope that the proposed technological solutions will be used in
modern construction practice. The authors are grateful to colleagues who took
part in experimental studies and in the preparation of this book for publication.

Contents

Preface iii

1. Introduction 1

2. Mineral Admixtures as Components of Cement Concrete 3

2.1 General Information about Mineral Admixtures for Concrete 3

2.2 Interaction in the “Mineral Admixture (admixture)—Mineral 6

Binder” System

2.3 Activation of Mineral Admixtures 10

2.4 General Characteristics of Fly Ash as Active Mineral 13

Admixture of Cement Concrete

2.5 Concrete Proportioning with Fly Ash Admixture 17

3. Self-compacting Ash-containing Concrete 29

3.1 Properties of Cement-fly Ash Pastes and Fresh Concrete 29

3.2 Strength Properties of Self-compacting Ash Containing Concrete 36

3.3 Durability of Self-compacting Concrete Containing Fly Ash 44

3.4 Proportioning and Optimization of Self-compacting Concrete 49

Compositions

4. Metakaolin as Mineral Admixture for Cement-based Composites 53

4.1 General Information about Metakaolin as Mineral Admixture 53

4.1.1 Genesis and Properties of Kaolin 53

4.1.2 Manufacturing and Properties of Metakaolin 56

4.1.3 Application Areas of Metakaolin 58

4.1.4 Multicomponent Admixtures Containing Metakaolin 59

4.2 Properties of Metakaolin and other Components of Cement 60

Pastes and Self-leveling High-strength Concrete

4.2.1 Properties of Metakaolin as Mineral Admixture 60

4.2.2 Properties of other Materials Applied in Research 64

4.2.3 Effectiveness of Metakaolin and Composite 67

Metakaolin-based Admixtures

4.3 Hydration and Structure Formation of Cement Pastes with 73

Metakaolin-based Admixture

4.3.1 Normal Consistency and Water Retention of Cement Pastes 74

4.3.2 Initial Structure forming of Cement Pastes 82
vi Metakaolin and Fly Ash as Mineral Admixtures for Concrete
4.3.3 Peculiarities of Hydration and Structure of Hardened 89

Cement Paste

4.4 Properties of Self-leveling Concrete Containing Metakaolin 102

4.4.1 Water Consumption and Workability of Fresh Concrete 102

4.4.2 Water Bleeding, Segregation and Air-entraining of 110

Self-leveling Concrete

4.4.3 Peculiarities of Fine Aggregate Impact on Properties of 117

Fresh Concrete

4.5 Properties of High-strength Concrete Containing Metakaolin 121

4.5.1 Compressive Strength of Concrete and Kinetics of 121

Hardening

4.5.2 Efficiency Factor of Metakaolin Application for 130

Self-leveling High-strength Concrete
4.5.3 Crack Resistance Parameters of Concrete 137

4.5.4 Durability Properties of Concrete 144

4.6 Other Types of Concrete Admixtures Containing Metakaolin 149

4.7 Peculiarities of Industrial Manufacturing of Concrete 154

Containing Metakaolin and Superplasticizer

4.7.1 Concrete Proportioning Method and Proportion 154

Optimization

4.7.2 Industrial Manufacturing of Concrete Containing 160

Metakaolin and Superplasticizer

5. Use of Complex Metakaolin Fly Ash and Blast Furnace Granulated 165

Slag in Reactive Powder Concrete (RPC)

5.1 Influence of RPC Structural Features on its Strength 166

5.2 Aggregates Grain Composition 172

5.3 Activity of Ash-metakaolin Compositions and their Effect on 177

Hydration and Structure Formation of Cement Stone

5.4 Influence of Ash and Slag Admixtures on Reactive Powder 189

Concrete Strength
5.5 Optimal Compositions of Reactive Powder Concretes 202

Containing Ash and Metakaolin

5.6 Influence of Hardening Temperature Modes on Reactive 217

Powder Concrete Strength

References 221

Index 231
1

Introduction

In recent decades, new generation concretes have been increasingly used in
construction. Their distinctive features are multicomponent, adjustable in a wide
range of operational properties and have high manufacturability. Concrete of this
type is characterized by a reduced specific consumption of cement per unit of
strength when its high values are reached, high energy efficiency and the ability
to minimize or eliminate vibration when compacting a concrete mixture and heat
treatment in the manufacture of products and structures.
Active mineral admixtures are an important component of concretes.
New generation concretes, in contrast to traditional ones, these admixtures are
introduced into compositions with superplasticizers, which significantly increases
their efficiency as a result of a significant improvement in the rheological
properties of the cement matrix.
As numerous studies have shown, the greatest effect is achieved when a
highly active mineral admixture-microsilica is introduced into concrete mixtures.
At the same time, special production of microsilica as an admixture in concrete
requires implementation of a rather complex energy-intensive technology of
high-temperature processing of silica materials, sublimation and subsequent
condensation of a finely dispersed amorphous material. Most commonly used is
microsilica dust obtained during gas cleaning at enterprises for ferrosilicon and
ferroalloys production. It has a limited distribution, its transportation, storage
and dosing is fraught with certain difficulties.
This book contains research results on obtaining self-leveling, self-
compacting, high-strength and reactive-powder concretes using such sufficiently
available mineral admixtures such as fly ash, metakaolin and their compositions.
In combination with superplasticizers, these mineral admixtures make it possible
to obtain an effect commensurate with the effect of microsilica addition. The
technological conclusions obtained by the authors can be used in the production
of the above-discussed effective concrete types and the expansion of their use in
construction.
2 Metakaolin and Fly Ash as Mineral Admixtures for Concrete
Active mineral admixtures are an important component of concretes.
In new generation concretes, in contrast to traditional ones, these admixtures
are introduced into compositions with admixtures of superplasticizers, which
significantly increases their efficiency as a result of a significant improvement in
the rheological properties of the cement matrix.
2

Mineral Admixtures as

Components of Cement Concrete

2.1 General Information about Mineral Admixtures
for Concrete
Mineral admixtures are finely dispersed mineral materials, added into concrete
mixtures in an amount that is usually higher than 5% to improve or provide
special properties to concrete. By origin, admixtures of this type can be natural
or technogenic. Mineral admixtures are divided according to their pozzolanic
activity into inert and active. The group of active admixtures or pozzolan includes
materials capable to react with calcium hydroxide at normal temperatures to
form compounds with binding properties. Calcium hydroxide sources at concrete
hardening are the main minerals that are part of Portland cement clinker and are
hydrolyzed by exposure to water.
Self-cementing materials containing a significant amount of calcium oxide
along with acid oxides (high calcium slags and ashes) are sometimes called
active hydraulic admixtures, emphasizing their ability to slowly harden in an
aquatic environment. For a more complete realization of such admixtures binding
potential, additional lime content from an external source, such as Portland
cement or lime, may be required. Classification of active mineral admixtures,
used in European countries and USA, is based on their activity, chemical and
mineralogical composition (Table 2.1).
Mineral admixtures are usually considered active if cement paste, made on
the basis of the admixture and slaked lime, has a setting end no later than 7 days
after mixing, and specimens from this paste remain water resistant 3 days after
setting. Activity of admixtures is measured by the amount of CaO in mg, absorbed
by 1 g of the admixture from a water lime mortar during 30 days. It ranges from
50 to 100 for fly ash and from 350 ... 400 mg of CaO or more per 1 g of highly
active mineral admixtures (silica fume, metakaolin). The mineral admixtures
activity is also determined using the microcalorimetric method according to the