CCS-4(20): Shotcrete for the Craftsman

CCS-4(20): Shotcrete for the Craftsman

DESCRIPTION

The purpose of this document is to provide the nozzleman an understanding of basic concrete technology and describe and illustrate how to properly place quality shotcrete.

Information in this workbook should be used as a guide to good practice. ACI 506.2, “Specification for Shotcrete,” and ACI 506R, “Guide to Shotcrete,” should also be consulted. Above all, the plans and specifications for a specific construction project must be followed.

DOCUMENT DETAILS

Pages: 92

ISBN: 9781641951135

TABLE OF CONTENTS

Preface 7

Chapter 1—What is shotcrete?

1.1—Introduction 9

1.1.1. Dry-mix shotcrete 9

1.1.2. Wet-mix Shotcrete 10

1.1.3 Comparison of the shotcrete processes 10

Chapter 2—What the shotcrete craftsman should know about concrete

2.1—What is concrete? 13

2.1.1 Aggregates 13

2.1.2 Paste 14

2.2—Fundamentals of concrete 15

2.2.1 Freshly mixed concrete 16

2.2.2 Workability 16

2.2.3 Consolidation 17

2.2.4 Hydration, setting time, hardening 17

2.2.5 Curing 18

2.2.6 Drying of concrete 18

2.2.7 Strength 19

2.2.8 Unit weight (density) 20

2.2.9 Resistance to freezing and thawing 20

2.2.10 Permeability and impermeability 20

2.2.11 Abrasion resistance 21

2.2.12 Shrinkage 21

2.2.13 Control of cracking 21

Chapter 3—Concrete materials

3.1—Cements 23

3.1.1 Portland cements 23

3.1.2 Special cements 25

3.1.3 Calcium aluminate cement (CAC) 25

3.2—Supplementary cementitious materials (pozzolans) 25

3.3—Aggregates 26

3.3.1 Maximum size of aggregate 27

3.3.2 Aggregate gradation (size distribution) 27

3.3.3 Harmful materials in aggregate 29

3.4—Mixing water 29

3.5—Admixtures 29

3.5.1 Accelerators 30

3.5.2 Set retarders 30

3.5.3 Water reducers 30

3.5.4 High-range water reducer 31

3.5.5 Air-entraining admixtures 31

3.5.6 Hydration control admixtures 31

3.5.7 Rheology-modifying admixtures 31

3.5.8 Shrinkage-reducing admixtures 31

Chapter 4—Shotcrete Materials

4.1—Shotcrete 34

4.1.1 Dry-mix shotcrete 34

4.1.2 Wet-mix shotcrete 35

4.2—Reinforcement 37

4.2.1 Reinforcing steel 38

4.2.2 Welded-wire fabric 38

4.2.3 Steel and synthetic fibers 39

Chapter 5—Mixture Proportioning

5.1—Water-cementitious materials ratio 41

5.2—Concrete proportioning for shotcrete 43

Chapter 6—Shotcrete Equipment

6.1—Equipment layout 45

6.2—Equipment operation 45

6.3—Dry-mix equipment 45

6.3.1 Single- and double-chamber guns 45

6.3.2 Continuous feed rotary guns 46

6.4—Wet-mix equipment 46

6.5—Air compressors 47

6.6—Mixing equipment 49

6.7—Hoses and nozzles 49

6.8—Scaffolding 50

6.9—Auxiliary equipment 51

6.9.1 Air lance (blow pipes) 51

6.9.2 Predampeners 52

6.9.3 Water booster pump 53

6.9.4 Lighting 53

6.10—Operation 53

6.10.1 Dry-mix shotcrete 53

6.10.2 Wet-mix shotcrete 53

Chapter 7—Preparation before Shooting

7.1—Earth surfaces 55

7.2—Forms 55

7.3—Existing concrete or masonry 56

7.4—Reinforcing steel 57

Chapter 8—Shotcrete Placement Principles and Techniques

8.1—General 59

8.2—Dry-mix shotcrete 62

8.3—Wet-mix shotcrete 62

8.4—Horizontal surfaces 63

8.4.1 Dry-mix shotcrete 63

8.4.2 Wet-mix shotcrete 64

8.5—Corners 64

8.6—Vertical surfaces 65

8.6.1 Bench shooting 65

8.6.2 Vertical layers 65

8.7—Overhead surfaces 67

8.8—Encasing reinforcing steel 68

8.9—Crew responsibilities 69

Chapter 9—Environmental Conditions and Precautions

9.1—Cold weather 73

9.2—Hot weather 74

9.3—Wind 74

9.4—Plastic shrinkage sracking 74

9.5—Curing 75

Chapter 10—Finish and Tolerance Controls

10.1—General 77

10.2—Tolerance 77

10.3—Finishing 77

Chapter 11—Safety

11.1—General 79

11.1.1 Cement burns 79

11.1.2 Inherent pressure risk 80

11.2—Equipment 82

11.2.1 Manlift 82

11.2.2 Dry-mix equipment 82

11.2.3 Wet-mix equipment 82

11.2.4 Hose line wear 83

11.2.5 Safety shroud 83

11.3—Communications 83

Chapter 12—Testing/Quality Control

12.1—Evaluating shotcrete material quality 85

12.2—Test panels 85

12.2.1 Material 85

12.2.2 Mockup panels 86

12.2.3 Finish 86

12.3—Care in handling and curing of shotcrete samples 86

Appendix A—Definitions 87

APPENDIX B—EVAPORATION RATE CHART 91