Manual of ready-mixed concrete

256 Pages·2003·7.544 MB·English

by  J D Dewar, R Anderson

Manual of Ready-Mixed
Concrete

J.D.DEWAR
Director
British Ready Mixed Concrete Association
and
R.ANDERSON
Product Officer
British Aggregate Construction Materials Industries

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This edition published in the Taylor & Francis e-Library, 2004.
First edition 1988
Second edition 1992
© 1992 Chapman & Hall
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ISBN 0 7514 0079 3 (Print Edition) 0 442 30866 3
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Preface
The first edition of this manual was warmly received as a straightforward and
well-written guide to the technology and practice of the ready-mixed concrete
industry. The industry is constantly changing, not only by a self-driven desire
to improve standards and quality, but also in response to the changing needs
of the marketplace, and the requirements to adapt to new and revised codes of
practice.
The manual has been completely updated to take account of changes in
British Standards—in particular those relating to concrete specification and
testing, and to cements. A particularly important inclusion is the concept of the
Designated Mix, which has been welcomed by the construction industry at
large as a major improvement to the way of specifying concrete for particular
end-uses. Throughout, we have also taken the opportunity to amend and add
to the text where we have perceived a need to present information and ideas
differently. As a result this revised edition is an improvement on the first
edition and should serve the needs of the market equally well.
We have retained the overall structure and format of the successful first
edition and, as before, to enable clear and logical presentation of the
information, the book is divided into two main sections: Part 1, Technology,
and Part 2, Practice. The Technology section provides the background to the
technical aspects of materials, concrete, control and testing, with the Practice
section dealing with methods of concrete production, specification,
construction, and quality assurance.
As before, the book is aimed at a wide readership within the construction
industry. It is equally relevant to the contracts manager, the site engineer, the
buyer working with a contractor, and will be of considerable value to the
consulting engineer, the architect and the quantity surveyor. It will be an
invaluable handbook for materials suppliers and testhouses and for all who
supply plant, equipment or materials, or who make, sell test or use ready-
mixed concrete. Lecturers and researchers in universities and colleges will
find it a useful source of reference.
JDD
RA
Acknowledgements
The authors gratefully acknowledge that many of the principles and methods described
are the distillation of years of experience generated by the many individuals who
collectively make up the ready-mixed concrete industry, its suppliers and its clients.
The net result may be taken as a summation of views for which the authors are
privileged to be the selectors and arbiters. Naturally, the authors take responsibility for
expressing the views and the facts and for any omissions or errors.
To minimize the risk of error, Mr B.V.Brown, Senior Technical Executive of Ready
Mixed Concrete (United Kingdom) Ltd, kindly read and commented upon the whole
of Part 1, and the authors are particularly grateful to him. On two specialized
subjects—cements and admixtures—thanks are due for expert comments from Mr
G.F.Masson, National Technical Manager, Blue Circle Industries plc, and Dr P.C.
Hewlett, Managing Director, Cementation Research Ltd and visiting professor at the
University of Dundee. For providing particular help with recent developments we wish
to thank Mr P.M.Barber (QSRMC) and Dr T.A.Harrison (BCA).
The comments and criticism of Mr P.E.D.Howes of ARC Ltd at the drafting stage
were much appreciated by both the authors, and material provided by Mr P.Male, then
of Steetley Quarry Products, Mr D.Bickley, then of Pioneer Concrete (UK) Ltd., and
Mr P.N.Staples of Tilcon Ltd., provided the basis for much of Part 2.
The following published papers have been used by permission of their authors and
publishers in suitably modified, updated or abbreviated forms: ‘BRMCA Guide:
Concrete Mixes, an Introduction to the BRMCA Method of Mix Design’, and
‘BRMCA Guide: BRMCA Concrete Control System’ (BRMCA); ‘Monitoring concrete
by the CUSUM system’ (B.V.Brown and the Concrete Society); ‘Ready Mixed
Concrete Mix Design’ (Municipal Engineer); Testing Concrete for Durability
(Palladian Publications); ‘Quality Scheme for Ready Mixed Concrete Technical
Regulations’ (QRSMC); ‘The workability of ready-mixed concrete’ (RILEM).
A number of tables and figures have been adapted from published papers as
acknowledged in the references. Particular thanks are due to the following for
permission to reproduce data, tables or figures: Mr F.W.Beaufait; Mr B.V.Brown;
Professor R.K.Dhir; Dr A.M.Neville; Mr K.Newman; Mr B.Osbaeck; Professor
S.Popovics; Mr R.Ryle; Mr R.E.Spears; ACI; BACMI; BRMCA; BSI; BCA; Concrete
International; The Concrete Society; Controller of HM Stationery Office; ERMCO;
Municipal Engineer; New Civil Engineer; Palladian Publications; Pitman Books Ltd;
Pergamon Press Ltd; RILEM; RMC Technical Services Ltd.
Extracts from BS 6089:1981 are reproduced by permission of BSI. Complete
copies can be obtained from them at Linford Wood, Milton Keynes MK 14 6LE.
Thanks are given to Mr Robert Phillipson, Director General of BACMI, for
permitting the text to be transferred to a BACMI word processor which has made the
editing and re-editing of drafts a far simpler task than it would have been otherwise.
We also thank the publishers for their support.
Contents

PART 1: TECHNOLOGY OF READY-MIXED CONCRETE
Introduction: History of ready-mixed concrete 3
1 Materials for concrete 9
1.1 Aggregates 10
1.1.1 Maximum aggregate size 11
1.1.2 Grading 12
1.1.3 Silt, clay and fine dust 16
1.1.4 Shape and texture 17
1.1.5 Water absorption 18
1.1.6 Relative density 18
1.1.7 Bulk density, void content and voids ratio 19
1.1.8 Moisture content 21
1.1.9 Chloride content 22
1.1.10 Deleterious materials 23
1.1.11 Shells 24
1.1.12 Uniformity 24
1.1.13 Non-standard aggregates 25
1.1.14 Making the best use of natural resources 25
1.1.15 Moisture movement 25
1.1.16 Lightweight aggregates 26
1.1.17 Heavyweight aggregates 27
1.2 Cementitious materials 28
1.2.1 Grading, mean size and fineness 29
1.2.2 Relative density 30
1.2.3 Water demand 30
1.2.4 Setting times 31
1.2.5 Strength at 28 days 33
1.2.6 Ratio of early to 28-day strength 35
1.2.7 Sulphate resistance 35
1.2.8 Alkali content 35
1.2.9 Chloride content 38
1.2.10 Colour 38
1.2.11 Ground granulated blastfurnace slag and pulverized-fuel ash 38
1.3 Admixtures 48
1.3.1 Accelerators 50
1.3.2 Retarders 50
1.3.3 Water-reducers (normal and superplasticizers) 50
1.3.4 Air entrainment 51
1.3.5 Superplasticizers 53
1.3.6 Pigments 54
1.3.7 Foaming agents 54
1.4 Other materials 54
1.4.1 Pfa to BS 3892: Part 2, Grade A 54
1.4.2 Silica fume (micro-silica) 54
1.4.3 Fibres 55
1.5 Water for concrete 55
vi CONTENTS
2 Properties of fresh concrete 56
2.1 Uniformity and stability 56
2.2 Workability 57
2.2.1 Workability test methods 57
2.3 Pumpability 60
2.4 Water demand and water/cement ratio 61
2.5 Rate of change of workability 63
2.6 Influence of transporting on the workability of ready-mixed concrete 64
2.6.1 Cement content 68
2.6.2 Aggregate grinding 68
2.6.3 Water content and initial workability 68
2.6.4 Admixtures 68
2.6.5 Ambient conditions 69
2.6.6 Bulk volume of concrete 70
2.6.7 Transporting method 70
2.7 Effects of transporting of concrete on strength and workability 70
2.8 Limitations on delivery time 71
2.9 Retempering of concrete 72
2.10 Laboratory simulation of ready-mixed concrete 74
3 Properties of hardened concrete 76
3.1 Surface quality 76
3.2 Cracking of concrete 76
3.3 Strength 79
3.3.1 Strength development with age 81
3.4 Durability 81
3.4.1 Concrete mobility 82
3.4.2 Covercrete and heartcrete 83
3.4.3 A background to specifying durability 85
3.4.4 Corrosion of reinforcement 86
3.4.5 Chlorides in concrete 86
3.4.6 Alkali-silica reaction 86
4 Mix design 88
4.1 Principles of mix design 88
4.2 BRMCA method of concrete mix design 88
4.2.1 Use of base data from BRMCA mix design method 90
4.2.2 Example: selecting batch proportions for specified design
mix requirements 94
4.2.3 Selection of batch proportions for a prescribed mix 95
4.2.4 Example: selecting batch proportions for a standard mix 95
4.2.5 The predictable future 96
4.2.6 Technical advice on concrete properties based on the BRMCA
method 97
4.3 Mix design using ggbs or pfa 98
4.3.1 Example: an adjustment to a mix design for the use of pfa 98
4.4 Judging concrete mix design 101
4.5 Water/cement ratio—free or total 102
4.6 Meeting durability requirements 103
4.6.1 Equivalent strength grades—ensuring durability 103
5 Statistics for quality control, mix design and compliance 105
5.1 Statistical terms 105
5.2 Variation 105
5.3 Distribution 106
5.4 Normal distribution 106
CONTENTS vii
5.5 Calculations of mean, standard deviation and other parameters 108
5.6 Sources of variation 109
5.7 Influence of mean strength level on standard deviation 110
5.8 Standard deviation due to sampling and testing 111
5.9 Relevance of standard deviation for concrete mix design 112
5.10 Statistical implication of compliance rules 112
5.10.1 Current compliance rules of BS 5328 113
5.10.2 Influence on producer’s risk of faults in sampling and testing for
compliance 117
6 Quality control 118
6.1 Forward control 119
6.2 Immediate control 120
6.3 Retrospective control 121
6.4 Quality monitoring 121
6.5 The cusum system of strength monitoring 122
6.5.1 Principles 122
6.5.2 Control of mean strength 123
6.5.3 Monitoring of standard deviation 124
6.5.4 Significance of trends 125
6.5.5 Design of masks 125
6.5.6 Advantages over other systems 126
6.5.7 Cusum for correlation of predicted and actual strength 127
6.5.8 Example: cusum in operation 128
6.5.9 Plotting cusum charts 129
6.5.10 Action following changes 132
6.5.11 Investigation of the cause of a change 134
6.5.12 Computerization 134
6.6 BRMCA concrete control system 135
6.6.1 Initial situation 135
6.6.2 Test data 135
6.6.3 Prediction of 28-day strength 135
6.6.4 Mean strength control (by counting rule) 138
6.6.5 Standard deviation 139
6.6.6 Early-28-day strength relationships 139
7 Sampling and testing ready-mixed concrete 140
7.1 Sampling ready-mixed concrete 140
7.2 Effects of non-standard testing on strength 140
7.3 Simple checks on validity of results 143
7.4 Communication 144
7.5 Simple visual checks on the crushed cube 144
7.6 NAMAS register of test houses 147
7.7 Interpreting test results for strength 149
7.7.1 Apparent compliance failures 149
7.7.2 Checking on validity 149
7.7.3 Action relating to valid compliance failures 151
7.7.4 Establishing strength of concrete in the structure 151
7.7.5 Interpretation of in-situ cube strength 154
7.7.6 Use of non-destructive testing 156
7.7.7 Remedial work 156
7.7.8 Increasing the strength and durability of concrete in the structure 157
7.8 Checking mix proportions or quantities 157
7.8.1 Analysis of fresh concrete 157
7.8.2 Chemical analysis of hardened concrete 158
7.9 Checking the quantity of concrete 159
7.9.1 Measuring construction volume 159
viii CONTENTS
7.9.2 Measuring volume to be concreted 160
7.9.3 Measuring volume of plastic concrete after finishing 160
7.9.4 Measuring volume of hardened concrete 160
7.10 Variation in density and yield 160
PART 2: PRACTICE
8 Production, delivery and quality assurance 165
8.1 Production methods 165
8.1.1 Material types 165
8.1.2 Storage capacity 166
8.1.3 Processing sequence 166
8.1.4 Truckmixer capacity and throughput 169
8.1.5 Planning requirements 170
8.1.6 Quality control requirements 170
8.1.7 Regulatory requirements 170
8.1.8 Duration of operations 171
8.1.9 Health and safety 171
8.2 Organizing production and delivery 171
8.3 Delivery 174
8.3.1 Truckmixers 174
8.3.2 Tippers 178
8.3.3 Conveyors 180
8.4 Quality assurance 180
9 Specifications and supervision 182
9.1 Interpreting specifications 182
9.1.1 Uses of concrete specifications 182
9.2 Specifying and supervising the supply of ready-mixed concrete 195
9.2.1 Specification clauses 195
9.2.2 Checking 198
9.2.3 Designated mixes 198
10 Ready-mixed concrete on site 200
10.1 Choosing ready-mixed concrete 200
10.1.1 Site mixing costs 200
10.1.2 Ready-mixed v. site mixing supply 201
10.1.3 Ready-mixed concrete plants on site 201
10.2 Site preparations for ready-mixed concrete 202
10.2.1 Site/supply liaison 202
10.2.2 Setting up a concrete supply 203
10.2.3 Programming concrete deliveries 203
10.3 Ready-mixed concrete on site 205
10.3.1 Delivery ticket 205
10.3.2 Addition of water at site 206
10.3.3 Safety 206
10.3.4 Delays 208
10.3.5 Placing the concrete 209
10.3.6 Compacting the concrete 212
10.3.7 Curing the concrete 212
10.4 Pumping concrete 212
10.4.1 The contractor 212
10.4.2 The pump hirer 213
10.4.3 The ready-mixed concrete supplier 213
CONTENTS ix
11 Organizations 215
11.1 BRMCA 215
11.2 BACMI 216
11.3 QSRMC 216
11.3.1 Technical standards 216
11.3.2 Order processing 216
11.3.3 Technical records 217
11.3.4 Plant and production 218
11.3.5 Continuing surveillance and enforcement 218
11.3.6 NACCB accreditation 218
11.4 NACCB 218
11.5 NAMAS 218
Appendix 1: QSRMC technical regulations 219
Appendix 2: Conversion factors 227
Appendix 3: Designated mixes in accordance with BS 5328:
Part 2 Section 5 229
References 233
References to standards 239
Index 241