Bartos P. J., Glassfibre Reinforced Concrete - Principles, Production, Properties and Applications, 2017

Glassfibre Reinforced Concrete

Glassfibre Reinforced Concrete Principles, production, properties and applications

Professor Peter J. M. Bartos

Published by Whittles Publishing, Dunbeath, Caithness KW6 6EG, Scotland, UK www.whittlespublishing.com © 2017 Peter J. M. Bartos ISBN 978-184995-326-9

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, recording or otherwise without prior permission of the publishers. Te publisher and authors have used their best efforts in preparing this book, but assume no responsibility for any injury and/or damage to persons or property from the use or implementation of any methods, instructions, ideas or materials contained within this book. All operations should be undertaken in accordance with existing legislation, recognized codes and standards and trade practice. Whilst the information and advice in this book is believed to be true and accurate at the time of going to press, the authors and publisher accept no legal responsibility or liability for errors or omissions that may have been made.

ypeset by Deanta Global Publishing Services, Chennai, India

Contents

x xiii xiv xv xvii

List of figures List of tables Acknowledgements Preface Glossary

1

Introduction and Scope

1

2

Brief History of Development

4

3

Constituent Materials 3.1 Binders 3.2 Aggregates 3.3 Fibres 3.3.1 Composition and basic properties 3.3.2 Size, shape and length 3.3.3 Alkali resistance 3.4 Admixtures 3.4.1 Plasticisers and superplasticisers 3.4.2 Viscosity-modifying agents 3.4.3 Accelerators and retarders for setting/hardening 3.4.4 itanium dioxide 3.4.5 Other admixtures 3.5 Polymers, pigments and additives/fillers 3.5.1 Polymers 3.5.2 Pigments

v

8 8 9 10 12 13 14 16 16 16 17 17 19 19 19 20

vi

Contents

3.5.3 Microsilica 3.5.4 Hydraulic additives 3.6 Water

21 21 22

4

Manufacture 4.1 Batching and mixing 4.2 Production of GRC elements 4.2.1 Premix and casting 4.2.2 Simultaneous spray-up 4.2.3 Other production methods 4.3 Curing 4.4 Moulds and formwork 4.5 Surface finishes and treatments 4.6 Handling, transport, storage and repairs 4.7 Cutting and shaping

23 23 25 27 28 29 32 33 35 39 40

5

Composite Action 5.1 Internal microstructure 5.2 Fracture mechanisms 5.3 Influencing factors 5.3.1 Mechanical properties of fibres 5.3.2 Mechanical properties of the matrix 5.3.3 Bond

41 41 41 47 47 48 49

6

Properties of GRC 6.1 Properties of fresh GRC 6.2 Properties of hardened GRC 6.2.1 Basic influencing factors and typical mix designs 6.2.2 Methods for assessment of performance 6.3 Physical properties

53 53 55 55 58 59

6.3.1 6.3.2 Density Permeability, water absorption and apparent porosity 6.3.3 Acoustic properties 6.3.4 Termal properties 6.4 Mechanical properties 6.4.1 Modulus of elasticity 6.4.2 Flexural/bending strength 6.4.3 ensile strength and Poisson’s ratio 6.4.4 Compressive strength 6.4.5 ransverse tensile and inter-laminar shear strength

59 60 60 61 62 62 64 65 66 67

Contents

vii

6.5 oughness and impact resistance 6.6 Durability 6.6.1 Wet/dry cycles 6.6.2 Freeze/thaw cycles 6.6.3 Fire resistance 6.6.4 Chemical, biological and other exposure 6.7 Volume (dimensional) changes 6.7.1 Effects of humidity: shrinkage/swelling 6.7.2 Creep and fatigue 6.7.3 Termal contraction/expansion 6.8 Self-cleaning 6.9 Environmental performance 6.9.1 Energy requirements 6.9.2 Environmental impact analysis 6.9.3 Active de-pollution of environment by eGRC 6.9.4 Recycling of GRC

68 69 69 70 70 71 71 72 72 74 74 75 75 76 78 80

7

Structural Design 7.1 Principles 7.2 ypical structural elements 7.2.1 Single-skin sheet 7.2.2 Ribbed panels 7.2.3 Sandwich panels 7.2.4 Stud-frame system 7.3 Fixings 7.3.1 Basic functions and design principles 7.3.2 ypes of fixings 7.3.3 Durability

81 81 82 82 83 83 85 86 86 88 91

8

Specification and Compliance

93

8.1 8.2 8.3 8.4

93 93 94 94 94 95 96 97 97

General guidance, selection Production quality grades controland andtheir compliance Sampling and frequency of tests esting 8.4.1 Content of glass fibres 8.4.2 Grade 8.4.3 Bulk density, water absorption and apparent porosity 8.4.4 Other tests 8.5 Dimensional tolerances

viii

Contents

8.6 Potential defects 97 8.6.1 Uneven fibre content and distribution 97 8.6.2 Inadequate or excessive thickness 98 8.6.3 Excessive cracking and crazing 98 8.6.4 Porosity, insufficient compaction and surface defects 99 8.6.5 Excessive efflorescence 100 8.6.6 Ghosting 100 8.7 Repair and remedial actions 100 9 Health and Safety

102

10 Summary of Benefits

104

11 Applications 11.1 Introduction 11.2 Mature structures 11.3 Civic/public buildings 11.4 Office and commercial buildings 11.5 Residential buildings 11.6 Religious structures 11.7 Art and recreation 11.8 Reconstruction/conservation of historic and contemporary buildings 11.9 Interior decoration and furniture 11.10 Architectural building components 11.11 Civil and environmental engineering

106 106 109 112 119 125 133 135

12 Standards

156

13 References

158

Appendix A: Calibration of GRC Spray Equipment A.1 Bag test A.1.1 Equipment A.1.2 Method A.1.3 Glass output A.2 Bucket test A.2.1 Equipment A.2.2 Method A.2.3 Slurry output

163 163 163 163 164 164 164 164 164

140 142 147 150

Contents

ix

A.2.4 Calculated examples A.2.5 Basic procedure A.3 Mini-slump test: measuring flow of slurry A.3.1 Equipment A.3.2 Method A.3.3 Notes

164 166 166 166 167 167

Appendix B: Determination of Glass Content of Uncured GRC B.1 Scope B.2 Definitions B.3 est specimen B.4 est procedure B.5 Calculation and expression of results B.6 est report

168 168 168 169 169 170 170

Appendix C: Determination of Flexural Properties of GRC C.1 Scope C.2 Definitions C.3 Apparatus C.4 est specimen C.5 Number of test specimens C.6 Procedure C.6.1 Conditioning of test specimens C.6.2 esting procedure C.7 Calculation and expression of results C.7.1 Limit of proportionality C.7.2 Modulus of rupture C.7.3 Directionality ratio C.8 est Report

171 171 171 171 172 173 173 173 174 174 174 174 175 175

Appendix D: Determination of the Dry and Bulk Density, Water Absorption and Apparent Porosity ofWet GRC D.1 Scope D.2 Apparatus D.3 est specimen D.4 est procedure D.5 Calculation and expression of results D.6 est report

177 177 177 177 178 178 178

Index

181

List of figures

3.1 3.2 3.3 3.4 3.5 4.1 4.2 4.3

4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13

Roving of AR glass fibres Chopped AR fibre strands A typical cross section of a strand of fibres – shown in a backlit section through GRC Dimensions of a standard specimen for the SIC test Outline of the photocatalytic activity at an ‘active’ eGRC surface exposed to natural light ypical GRC 125 Combination high shear batch mixers Integrated automated batching/mixing plant (a) Spring rollers for manual compaction of fresh GRC; (b) manual compaction of a highly profiled GRC element using a roller Spray gun for the premix-spray process (a) Concentric spray gun; (b) in action A thickness gauge being used to measure the thickness of a GRC sheet during production Section through light-transmitting glass fibre concrete Details of lattice truss elements produced by 3-D printing of GRC Polyurethane rubber mould being stripped off Mould for production of a prototype GRC panel forming a section of a large dome Principle of the ‘adaptive mould’ system for production of moulds for double-curved GRC elements Production of a GRC element using the ‘adaptive’ mould process Handling of a large GRC panel x

12 12 13 15 18 24 25

26 27 28 29 31 32 34 35 36 36 39

List of figures

4.14 A laser beam cutting through a sheet of GRC 4.15 A GRC sheet with a very precisely cut hole using a laser beam 5.1 Cross section of GRC showing strands of glass fibres 5.2 A composite of microphotographs of the three typical modes of tensile fracture of strands of glass fibres embedded in a cementitious matrix and crossing a crack in the GRC 5.3 Flexural test fracture surface – premix GRC 5.4 Fracture of a strand of fibres crossing a crack at an angle during a test within an SEM 5.5 ypical shapes of load-deflection (stress-strain) diagrams of GRC in bending 5.6 Cross section of a single glass fibre within a strand, split by a sharp diamond indenter in a nano-indentation ‘push-through’ test 6.1 Basic arrangement of the (mini) slump test for fresh slurry 6.2 Baseplate and mould for the mini-slump test 6.3 Reduction in transmission of sound in relation to mass of a panel 6.4 Layout of the standard flexural (bending) test on GRC 6.5 ypical test jig for the standard bending test 6.6 Development of LOP and MOR with age 6.7 ypical stress-strain diagram for GRC in tension 6.8 ypical shear-loading conditions 6.9 Dimensional changes related to humidity of service environment 6.10 Magnitude of the creep strain related to age and level of the applied flexural stress 6.11 Flexural fatigue of GRC (5% of fibres; w/c = 0.33) as a function of peak stress 6.12 Environmental parameters: between precastimpact concrete and GRCcomparison 6.13 De-pollution of air by photocatalysis on a road surface 7.1 ypical shapes of single-skin GRC panels 7.2 ypical shape of a box-ribbed panel 7.3 ypical shapes of sandwich panels 7.4 Tin-walled hollow sections in galvanised steel with anchors, ready for the assembly of a stud-frame GRC panel 7.5 ypical arrangement of a GRC stud-frame panel 7.6 Fixing through embedded inserts

xi

40 40 42

43 43 45 46

51 54 54 61 64 64 65 65 67 72 73 74 77 79 82 83 84 85 86 88

xii

List of figures

7.7

Basic arrangement of a bonded fixing. Te bonding pad envelops the anchor Guidance on the minimum size of a bonding pad with a flex anchor (a) A typical flex anchor; (b) its degrees of freedom of movement (a) Gravity anchor attached to the frame; (b) indication of the load paths Cast-in dowel bar connection ‘Hidden’ face fixing A defective rib in a GRC panel. Te rib-former (polystyrene) was not adequately held down, and a void ‘A’ developed Incorrect formation of a rib Stainless steel mesh basket for washing out of the test specimen Standard test for GR in bending – general layout ypical load-extension curve recorded in the test for bending strength

7.8 7.9 7.10 7.11 7.12 8.1 8.2 B.1 C.1 C.2

89 89 90 90 91 91 99 99 169 172 175

List of tables

3.1 3.2 3.3 6.1

ypical composition of an AR glass ypical physical and mechanical properties of AR glass fibres Specification for acrylic polymer admixtures (for curing) Guide to selection of grades of GRC for typical application

6.2

Premix grades 8, 8P, 10 and 10P, and sprayed grades 18 and 18P 6.3 Densities of typical GRC mixes 6.4 Range of properties achieved by a typical hardened premix or sprayed GRC 6.5 Environmental impact of GRC and precast concrete drainage channels 6.6 Environmental impact of GRC and precast concrete cable ducts 8.1 Performance of GRC using spray and premix processes 8.2 LOP and MOR of three basic grades of GRC 8.3 Values of LOP and MOR for assessment of compliance with specification A.1 Bag and bucket calibration data or 5% glass content C.1 Major and minor span and crosshead speed for various specimen thicknesses

xiii

13 14 20 56 57 59 63 76 77 95 95 96 165 173

Acknowledgements

Te author wishes to thank all who helped him in the development of this publication, particularly Graham . Gilbert for valuable information and comments, Peter Ridd for providing numerous technical and project data, Glyn Jones for input on structural design, Ian White for advice on production processes and for reading of the manuscript and Neil Sparrow for access to the International Glassfibre Concrete Association (iGRCA) pictorial archive. Te author wishes to acknowledge the inspiration and personal guidance provided by Professor Howard G. Allen of the University of Southampton at the very beginning of the development of GRC, whose predictions of wide use of GRC in the future have been now matched and even exceeded. Te book was produced with the assistance of the iGRCA, for which the author is grateful. However views expressed in this publication are those of the author and do not necessarily reflect those of the iGRCA.

xiv

Preface

Te development of glassfibre reinforced concrete (GRC) in the 1960s [1–4] exploited an ancient and simple principle of converting naturally brittle materials into much tougher and therefore more useful ones through the incorporation of strong fibres, initially of plant srcin. GRC is based on the same principle, and in the twenty-first century it is an already well-established construction material used all over the world. Basic constituents of GRC are very few, namely cement, water, fine aggregate and glass fibres. However, the internal structure of the composite itself is as complex as that of the most advanced high-tech materials, such as composites used in the aerospace industry. Paradoxically, a high-performance material such as GRC can also be reliably produced using relatively simple and inexpensive processes. Te range of its applications is already very wide. In its basic form, it is used to produce simple items such as ornamental flowerpots; while in its hightech version, it is the preferred construction material for the production of large, thin-walled structural elements of very complex shapes. GRC is a cement-based composite strongly related to concrete. However, in order to exploit its outstanding properties, substantial additional knowledge and understanding are required. Applications which utilise high-performance GRC do not require an excessively sophisticated and expensive production plant, but they do require a very strict production regime. An adequate level of supervision is much closer to that used for the production of highperformance, polymer-based, fibre-reinforced composites than to the manufacture of ordinary precast reinforced concrete products. GRC continues to develop (for example, eGRC). Numerous scientific and technical papers which focus on specific aspects of GRC exist. Many of these have been published together in the proceedings of congresses held by the xv

xvi

Preface

International Glassfibre Reinforced Concrete Association (iGRCA) every 2–3 years from 1977 [5] to date, while others have appeared in scientific and technical journals. However, all of the books which surveyed existing knowledge [6–8] were published in the earlier stages of GRC’s development, the last one being published in the early 1990s. Growth in the use of GRC since the turn of the twenty-first century has been and continues to be very strong. Tere is therefore a need to review the current stage of development and the applications of GRC. Tis book reviews historical background, indicates raw materials and outlines the different production processes and properties which can be achieved. Recent developments are highlighted, and the book illustrates the very wide range of GRC applications. At the same time, recent growth in the range and volume of practical applications has not been matched by advances in the understanding of this complex composite. Fundamental and unique aspects of the microstructure and fracture mechanism of GRC are outlined and discussed, without going into details, which are available in previous publications. Tis book shows that the full potential of GRC as a structural material has not yet been realised, and that a comprehensive understanding of GRC has yet to be achieved. An improved understanding is a prerequisite for successfully taking on the challenge of further improving its already outstanding properties and providing a solid background to an even greater use of advanced GRC in practical construction. It is a big challenge, requiring not only the highest level of investigative skills and background knowledge on the part of the researcher, but expensive, state-of-the-art research facilities as well. Compared to other widely used construction materials, GRC is one which has so far benefited the most from the exploitation of nanotechnology such as admixtures designedat molecular scale, investigation of bond using nanoscale apparatus, and nanoparticles in photocatalytic surfaces. Most importantly, substantial additional funding is required to make all the advances achieved in basic research by practitioners in the construction industry. Unfortunately, designuseable and manufacture of GRC are carried out almost entirely by small- and medium-sized companies, which even in the best of times do not have adequate internal resources to support research and development (R&D). It is therefore essential that national and international R&D funding authorities recognise this and provide assistance to the GRC industry to keep it moving forward. PJMB

Glossary

Additive Material other than cement or aggregate added to the GRC mix in a significant proportion (usually >5% by weight). Admixture A substance added in small quantities, usually