High Strength Concrete A practical guide By Michael A Caldarone

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High Strength Concrete A practical guide By Michael A Caldarone

Contents

List of illustrations x
Preface xiii
Acknowledgments xviii
List of abbreviations xix
1 Introduction 1
Unit conversions 2
Terminology 2
Historical background 12
Applications 15
References 20
2 Constituent materials 21
Introduction 21
Cementitious materials 21
Aggregates 48
Water 53
Chemical admixtures 54
Air-entraining admixtures 59
References 61
3 Mixture proportioning and evaluation 64
Introduction 64
Identifying relevant concrete properties 65
Statistical variability 67
Proportioning considerations 68
Designated acceptance age 84
ACI 318 code requirements for strength acceptability 85
Trial evaluation 86
Proportioning high-strength concrete: an example 88
References 96
4 Properties 99
Introduction 99
Mechanical properties 99
Durability properties 115
Constructability properties 124
References 126
5 Specifications 131
Introduction 131
Prescriptive vs. performance-based specifications 131
The pitfalls of arbitrarily established limits 133
The relevancy of the slump test 135
Constituent materials 136
Quality management plans 136
Producer qualifications 137
Submittals and conditions of sale 138
Testing laboratory qualifications 139
Preconstruction conferences 139
Post-28-day designated acceptance ages 140
References 142
6 Production and delivery 143
Introduction 143
Order taking 144
Dispatching 144
Quality control 145
Plant operations 147
Delivery 150
References 152
7 Placement, consolidation, and finishing 153
Introduction 153
Preconstruction conferences 154
Preparation 155
Placement 155
Consolidation 159
Finishing 159
Case study: When self-consolidation is not enough 160
References 162
8 Curing 164
Introduction 164
Moisture requirements 166
viii Contents
Temperature requirements 171
Curing high-strength precast concrete 171
References 173
9 Quality control and testing 174
Introduction 174
Testing variables influencing compressive strength 175
Standard cured vs. field cured specimens 186
In-place evaluation 187
Profiling constituent materials in the laboratory 191
Case Study: Jobsite curing in limewater 193
References 197
10 Problem solving 200
Introduction 200
Incompatibility 200
Early stiffening and erratic setting 211
Poor strength development 212
Aesthetic defects 213
Petrography 218
Case study: When color becomes a concern 221
Case study: An autogenous shrinkage cracking
investigation 223
References 225
11 Summary 226
Glossary 237
Institutes and standard writing organizations 242
Index 245

Illustrations

Figures
1.1 Office building at 225 West Wacker Drive, Chicago 14
1.2 Two Union Square, Seattle 15
1.3 Cross section and prestressed strand patterns Texas
U54 beams 17
1.4 Parking structure at 900 N. Michigan Ave, Chicago 18
1.5 The super skyscraper Burj Dubai 18
1.6 An extraordinary increase in attainable building height 19
2.1 Micrograph of Type I Portland cement 23
2.2 Portland cement clinker 24
2.3 Relative reactivity of cement compounds 25
2.4 28-day compressive strength of two concretes 28
2.5 A micrograph of fly ash showing typical spherical
particles 33
2.6 Compressive strength of concretes produced with
fly ash 35
2.7 Common setting characteristics comparing low and
high calcium fly ashes 36
2.8 Particle size comparison of conventional and ultra-fine
fly ash 39
2.9 Micrographs of conventional fly ash and ultra-fine
fly ash 40
2.10 Micrograph of ground granulated blast-furnace slag
grains 41
2.11 Scanning electron microscope micrograph of silica
fume particles 43
2.12 Micrograph of densified silica fume 46
2.13 Scanning electron microscope micrograph of metakaolin
particles 47
2.14 Effects of aggregate type and blend on mean 28-day
compressive strength 52
3.1 Illustration of the relationship between W/B ratio and
strength 72
3.2 Schematic representation of two fresh cement pastes 73
3.3 Illustration of interfacial transition zone 75
3.4 Effect of cement content on compressive strength at
28 days 77
3.5 Strength efficiency of Portland cement 78
4.1 Typical stress-strain relationship for high-, moderate-,
and conventional-strength concrete 101
4.2 As compressive strength increases, failure takes on an
increasingly explosive mode 102
4.3a (SI units) Measured modulus of elasticity at 28, 91,
and 426 days 104
4.3b (inch-pound units) Measured modulus of elasticity at
28, 91, and 426 days 105
4.4 Measured modulus of elasticity at 91 days 105
7.1 Placement of high-strength concrete simultaneously
with conventional-strength concrete 157
7.2 Honeycombs in monolithic spandrel beams 161
8.1 Severe plastic shrinkage cracking caused by ineffective
interim curing 167
9.1 Effect of high temperature initial curing 180
9.2 Initial jobsite curing by immersion in lime-saturated water 181
9.3 Temperature controlled jobsite-curing box 182
9.4 Transportation boxes 183
9.5 Improper storage of test cylinders
9.6 Rebound number determination using a “rebound
hammer” 184
9.7 Evaluating surface hardness by means of penetration
resistance method 189
9.8 Deviation from average strength at 3 days 190
9.9 Deviation from average strength at 7 days 194
9.10 Deviation from average strength at 28 days 194
9.11 Deviation from average strength at 56 days 195
9.12 Initial jobsite curing by immersion in lime-saturated
water 196
10.1 Profile of normal paste hydration 201
10.2 Illustration of an ideally balanced paste during the early
stages of cement hydration 202
10.3 Illustration of an “under-sulfated” paste 202
10.4 Illustration of an “over-sulfated” paste 203
10.5 1-day strength values for mortars made using cement
with various levels of sulfate, Class C fly ash used as
a 25 percent cement replacement, and a carbohydratebased
water-reducing admixture 206
10.6 The “mini-slump” test performed on paste samples 208
10.7 Mini-slumps pats taken at 2, 5, 10, 30, and 45
minutes 209
10.8 Examination of thin sections using a polarized-light
microscope 219
10.9 Air voids cluster along the periphery of a coarse
aggregate particle 220
10.10 Thin-section photomicrograph showing concrete
damaged by expansive alkali-silica reaction (ASR) 221
10.11 Color contrast of darker column concrete with slab
concrete 222
Tables
2.1 Bulk specific gravity of cementitious materials 22
2.2 Abbreviated notations used in cement chemistry 24
2.3 Primary compounds in Portland cement clinker 24
2.4 Various forms of calcium sulfate (CaSO4) 26
2.5 American (ASTM) and Canadian Standards Institute
(CSA) Portland cement classification 27
2.6 European (EN) “common cements” 27
2.7 ASTM C 595 classification for blended hydraulic
cements 29
3.1 Example constituent material combinations for pastes
of varying W/B ratios 88
3.2 Constituent materials used in first series of laboratory
trials 90
4.1 Coefficient of thermal expansion of various structural
concrete aggregates 114
9.1a Example mixtures used for laboratory evaluation of
various cement samples (SI units) 192
9.1b Example mixtures used for laboratory evaluation of
various cement samples (inch-pound units) 192
xii Illustrations

Preface

My purpose for writing this book is principally to provide those who
specify, produce, test, and construct with high-strength concrete practical
guidance about a material that continues to be viewed as mysterious, exotic,
and to some degree, even experimental. My hope is that this book will also
aid the reader in understanding the fundamental mechanics of how structural
concrete in general, not just high-strength concrete, works. High-strength
concrete is not a new material. The availability of commercially produced
high-strength concrete can be traced back to the late 1950s. In many markets
worldwide, the commercial availability of concretes capable of developing
compressive strength three to five times greater than typical conventional
concrete is well established. In other markets, high-strength concrete is still
considered novel.
As all new technologies are born in the research laboratory, intellectual
concentrations naturally shift from primarily academic interest to practical
and economic applicability. While the academic community continues to
research and publish ways in which to expand the feasible boundaries of
new materials and design methodologies, a shift from theoretical feasibility
to practical applicability occurs. Once the transition from research laboratory
to real world takes place, the amount of information published about
the technology, and its practical applications, decreases.
Although the topic of this book is high-strength concrete, it does not
define “high strength” by any single numerical value. My preference is
to define “high strength” relative to what might be considered as “normal”
or “conventional” strength in the geographic location it is being produced.
Even though high-strength concrete usually accounts for no more than a
very small fraction of all of the concrete used in modern construction, my
personal appreciation for this material is not limited to the ability of making
it in and of itself, but more so, the practical knowledge gained that is
applicable to conventional concrete also. So even though the primary subject
of this book is high-strength concrete, it should come as no surprise to the
reader that it also contains information dealing with conventional concrete.
Discussing the rationale supporting the technology of high-strength concrete
in relation to conventional concrete is far more beneficial than simply
presenting a set of guidelines and empirical relationships merely for purposes
of rote memorization. Stated differently, simply knowing that two plus two
equals four has far less potential for advancement compared to knowing
why two plus two equals four.
Several key considerations were addressed prior to writing this book.
First, is the presumption that the reader is generally familiar with both the
fundamental terminology and basic principles associated with concrete
technology.1 With this in mind, the reader may find that some concepts
considered fundamental to concrete technology have, for the most part,
been omitted. In the event of an unfamiliar term, material property, or
construction practice being encountered, several informative publications
are suggested at the beginning of Chapter 1. Second, to be consistent with
the book’s title, only concrete-making materials, production methods, and
construction practices considered “mainstream” to the industry will be
covered. Exotic materials and manufacturing processes will not be addressed.
This book will address high-strength concrete made using the same type
of cements, aggregates, admixtures, and water that can be used to produce
conventional-strength concretes.
There is a unique set of challenges for authors whose mission it is to
write a book about concrete meant for an international audience. Each
country has its own set of standards for concrete and its constituents. The
true challenge for authors or academics when attempting to absorb the
seemingly countless number of standards is that no international criteria
for measuring concrete properties or defining the physical characteristics
of concrete and its constituents yet exist. The exercise is like attempting to
assimilate a set of books written in multiple languages, presumably about
one particular area of knowledge, that are virtually non-translatable.
Fortunately, international standardization attempts are being made with
organizations such as the European Committee for Standardization (CEN).
Unfortunately, it may take many years before such harmonization occurs
on a global scale. In fact, with the vast amount of knowledge that has been
collected about concrete and its constituents in modern times, the absence
of more universally-oriented standards is an unfortunate roadblock to the
concrete industry worldwide. Since the standards and test methods that
apply to concrete vary so significantly worldwide, unless considered central
to the subject at hand, much of the information presented will refer largely
to North American guides and standards published by organizations such
as the American Concrete Institute (ACI) and American Society for Testing
and Materials (ASTM).
Compared to conventional-strength concrete, the use of high-strength
concrete offers a multitude of advantages considering both the technical
and economical aspects. The prime objective of this book is to provide the
reader with an understanding of the principles and methodologies associated
with the commercial applicability of high-strength concrete. Doing so will
require identifying some popular myths and misconceptions about concrete.
This book was not written with the implicit intention of identifying common
misunderstandings or misconceptions rooted within the concrete industry;
however, in order to satisfy the prime objective, it will occasionally be
necessary to distinguish the myth from the fact. Without doing so, it would
be much more difficult to develop a comprehensive understanding of why
the principles governing high-strength concrete can be so different from
those governing concrete of a more conventional strength.
The most notable evolutionary period thus far in the development of
ready-mixed high-strength concrete unquestionably occurred in Chicago
between the years 1960 and 1990. It was in Chicago, during the early
1960s, that a “perfect storm” of opportunity for the development of commercially
available high-strength concrete came together. What emerged
was nothing less than a golden age in the history of a state-of-the-art
construction material. In 1962, high-strength concrete with a design
compressive strength of 42 MPa (6000 psi) was supplied to Chicago’s 40-
story Outer Drive East high-rise condominium project. At that time, the
commercial availability of 40 MPa (6000 psi) was considered a breakthrough.
By 1989, commercially available concrete with a design strength
of 96 MPa (14,000 psi) was supplied for six stories of columns along with
one 117 MPa (17,000 psi) experimental column at the 225 W. Wacker
project (Moreno, 1990). What came together was a rapidly growing highrise
building market and an engineering community ready to reap the
advantages that come with higher-strength materials; high-quality locally
available raw materials (including the new “chemical” admixtures that
were making their way into mainstream industry), and lastly, at the focal
point of it all was a premier ready-mixed concrete producer with a progressively
minded technical staff. The company was Material Service Corporation
(MSC) and the individuals principally responsible for the birth and continual
evolution of high-strength concrete in Chicago were Ron Blick, Ralph
Vencil, Mike Winter, Chuck Peterson, John Albinger, Art King, and Mike
Pistilli.
Since the early 1960s, the market demands, material supply, and knowledge
in the art and science of making high-strength concrete came together
in Chicago. In order for all the necessary components to come together
and make it possible, there was one more critically essential element needed.
In the case of high-strength concrete in Chicago, the essential element
prompting the coming together of high-strength material and design was
the communication between the material supply and design communities.
For those familiar with both materials engineering and structural design,
it will come as no surprise that structural engineers and materials engineers
appear to speak different languages. If it had not been for the efforts of
the technical and engineering staff, and individuals like Jaime Moreno,
working side by side with local designers, the author does not believe that
the evolution that took place in Chicago could ever have been possible. In
three short decades, there was nearly threefold increase in commercially
available compressive strength. The history of high-strength concrete is
covered in more detail in Chapter 1.
My personal interest in materials engineering can be traced back to the
inspiring lectures of my first materials engineering instructor, Dr Antoine
Naaman, at the University of Illinois, Chicago. My personal interest in
high-strength concrete was born during a field trip to Material Service Yard
No. 1 near downtown Chicago. Dr Naaman arranged this field trip every
semester for his students. In fact, it was on the day of that field trip that
I suspected (or at least hoped) where my future interests would lie. Just
before the tour bus departed, I recall Art King’s final words and the profound
effect they would have on my life—“and remember Material Service makes
good concrete.” Years later, I reminded myself how important it is to
maintain a focus on long-term objectives because, in 1989, I was offered
a position with MSC. Although the evolutionary years of high-strength
concrete in Chicago was in its twilight, the five years I spent in the Quality
Control Department at MSC under the guidance of Art King was an excellent
personal opportunity in and of itself. Sadly, in 1994, as a purely business
decision, MSC sold its ready-mixed concrete operation.
Of course, Chicago was not the only place where great things happened
with high-strength concrete. What happened in Chicago became a great source
of inspiration for others. Interestingly, in the preface of his book (Aïtcin, 1998),
Professor Pierre Claude Aïtcin of University of Sherbrooke wrote:
My first exposure to high-strength concrete dates back to 1970, when
I first heard John Albinger of Material Service make a presentation on
the high-strength concrete he was delivering in the Chicago area at that
time. He was so convincing and enthusiastic about high-strength concrete
that I decided to end my concrete class at the University of Sherbrooke
every year with a contest whose objective was for my students to make
the strongest concrete with a maximum amount of cement and supplementary
cementitious materials of 600 kg/m3 (1000 lbs/yd3).
Unlike Dr Aïtcin, when I first met John Albinger in the mid-1980s, my
interest in high-strength concrete was already solidly established, thanks to
Dr Naaman’s thoughtfully planned student field trips. John’s passion and
enthusiasm about high-strength concrete had not waned. Looking back,
there is no question that John Albinger was a major source of inspiration
for me. Passion about one’s chosen field is both marvelous to have and
difficult to hide.
The intention of this book is to pass on as much useful, practical information
that the forthcoming pages will allow. This book, in many respects,
expands upon the principles contained in American Concrete Institute’s
State-of the-Art Report on High-Strength Concrete published by Committee
363. Also included is knowledge learned over the past 20 plus years from
colleagues, along with some “real world” case studies.
There is countless advancement still to be made in the field of cement
and concrete. Scientists, mathematicians, and engineers, including Sir Isaac
Newton (1642–1727), recognized that most advancement in knowledge is
built upon the achievements of those who came before them. In a letter
to fellow scientist Robert Hooke on February 5, 1676, Newton modestly
wrote: “If I have seen further it is by standing on the shoulders of giants.”
To illustrate, Newton’s Law of Gravitation, which could be used to mathematically
describe, among other things, planetary motion, was developed
using the highly precise calculations of Johannes Kepler (1571–1630).
Kepler’s contributions to scientific knowledge, on the other hand, may
never had occurred had he not stood on the shoulders of giants with such
names as Galileo (1564–1642), Brahe (1546–1601), and Copernicus
(1473–1543).
Although perhaps not as intriguing as planetary physics, the evolution
of knowledge in the field of cement and concrete is no different. In industry
and academia, there are many great shoulders yet to be climbed.