Table of Contents
Preface ix
Acknowledgements x
1 The importance of workability 1
1.1 The meaning of workability 1
1.2 Definition of workability 5
1.3 Terminology 7
1.4 Subjective assessment of workability 8
1.5 Empirical methods-of measurement 9
1.6 References 10
2 Standard tests for workability 11
2.1 Sampling 13
2.2 The slump test 14
2.3 The compacting-factor test 16
2.4 The Vebe consistometer 19
2.5 The flow-table test 21
2.6 Ball-penetration test 27
2.7 Precision of the standard tests 28
2.8 General criticism of standard tests 31
2.9 References 34
3 Flow properties of fresh concrete 37
4 Principles of measurement 47
5 The two-point workability test 54
5.1 Principles 54
5.2 Development 55
5.3 The apparatus 57
5.4 Modification for low-workability concretes 59
5.5 Use of the apparatus 62
5.6 Experimental error 64
5.7 Oscillation of torque 66
5.8 Theoretical considerations 67
5.9 Results 70
5.10 References 73
6 Workability expressed in terms of two constants 74
6.1 Restricted validity of single-point tests 77
6.2 Significance of single-point tests 80
6.3 References 87
7 Extremely low-workability concretes 88
7.1 References 93
8 Factors affecting workability: Time and properties of mix components 94
8.1 Introduction 94
8.2 Time 95
8.3 Properties of aggregates 99
8.4 Cement properties 111
8.5 References 119
9 Effect of mix proportions 121
9.1 Water content 121
9.2 Aggregate : cement ratio and fines content 123
9.3 Segregation and bleeding 131
9.4 Segregation during testing 135
9.5 References 137
10 Effect of chemical admixtures 139
10.1 Plasticizers and superplasticizers 139
10.2 Air entrainment 151
10.3 Combined effects 152
10.4 References 155
11 Effect of cement replacements and fibres 156
11.1 Introduction 156
11.2 Pulverised fuel ash 157
11.3 Microsilica 162
11.4 Blast furnace slag 164
11.5 Fibres 169
11.6 References 175
12 Workability and practical processes 176
12.1 Mixing 176
12.2 Pumping 180
12.3 Vibration 184
12.4 References 199
13 Specification of workability 202
13.1 Specification in terms of the two-point test 205
13.2 References 212
14 Workability measurement as a means of quality control 214
14.1 Introduction 214
14.2 General principles of quality control 215
14.3 Present practice 215
14.4 Possibilities in testing for control 222
14.5 Control potential of the two-point test 223
14.6 Quality assessment without preliminary investigations 224
14.7 Quality assessment with preliminary investigations 232
14.8 Prediction of strength 234
14.9 Establishing a control system 237
14.10 References 242
15 Epilogue 243
Glossary 245
Appendix: BS 5328:1990 252
Conversion factors 255
Author index 257
Subject index 259
