GEOMATERIALS UNDER THE MICROSCOPE A COLOUR GUIDE building stone, roofing slate, aggregate, concrete, mortar, plaster, bricks, ceramics, and bituminous mixtures Jeremy P. Ingham BSc (Hons), MSc, DipRMS, CEng, MInstNDT, EurGeol, CGeol, CSci, FGS, FRGS, MIAQP MANSON PUBLISHING Copyright © 2010 Manson Publishing Ltd ISBN: 978-1-84076-132-0 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system ortransmitted in any form or by any means without the written permission of the copyright holder or in accordance with the provisions of the Copyright Act 1956 (as amended), or under the terms of any licence permitting limited copying issued by the Copyright Licensing Agency, 33–34 Alfred Place, London WC1E 7DP, UK. Any person who does any unauthorized act in relation to this publication may be liable to criminalprosecution and civil claims for damages. A CIP catalogue record for this book is available from the British Library. For full details of all Manson Publishing titles please write to: Manson Publishing Ltd, 73 Corringham Road, London NW11 7DL, UK. Tel: +44(0)20 8905 5150 Fax: +44(0)20 8201 9233 Website: www.mansonpublishing.com Commissioning editor: Jill Northcott Project manager: Kate Nardoni Copy editor: Joanna Brocklesby Book design and layout: Cathy Martin Colour reproduction: Tenon & Polert Colour Scanning Ltd, Hong Kong Printed by: Butler, Tanner & Dennis, Frome, UK CONTENTS Preface 5 Chapter 4 Aggregates 61 Acknowledgements 5 Introduction 61 Author profile 5 Petrographic examination and complementary Abbreviations 6 techniques 61 Aggregate type 61 Chapter 1 Aggregate grading, shape, and surface texture 64 Introduction 7 Soundness, impurities, and undesirable Overview of geomaterials and petrography 7 constituents of aggregates 66 Petrographic techniques 10 Potential alkali-reactivity of aggregate for Sampling and sample preparation 14 concrete 69 Matching aggregates for conservation 74 Chapter 2 Building stone 21 Chapter 5 Introduction 21 Concrete 75 Testing building stone 22 Introduction 75 Petrographic examination and complementary Assessment of concrete structures 75 techniques 24 Petrographic examination and complementary Stone from igneous rocks 24 techniques 76 Stone from sedimentary rocks 32 Investigating the composition and quality of concrete 76 Stone from metamorphic rocks 44 Examining deteriorated and damaged concrete 96 Petrography of stone defects and decay 47 Chapter 6 Chapter 3 Concrete products 121 Roofing slate 51 Introduction 121 Introduction 51 Petrographic examination 122 Testing roofing slates 51 Architectural cast stone 122 Petrographic examination and complementary techniques 52 Aircrete products 124 Properties of roofing slates 52 Calcium silicate units 124 Weathering and deterioration of roofing slate 56 Asbestos cement products 126 Interpretation of slate test results 58 4 Chapter 7 Chapter 10 Floor finishes 129 Bituminous mixtures 171 Introduction 129 Introduction 171 Petrographic examination 130 Petrographic examination 172 Floor screed 130 Examples of bituminous mixtures 172 Terrazzo 132 Synthetic resin floor covering 133 Appendix A 175 Suppliers of petrographic equipment, training, and literature 175 Chapter 8 Mortar, plaster, and render 137 Overview 137 Appendix B 176 Gypsum-based 139 Staining techniques for geomaterials petrography 176 Lime-based 143 Etching and staining techniques for cement Portland cement-based 152 minerals and slags 178 Specialist mortars 159 References and further reading 180 Chapter 9 Bricks, terracotta, and other ceramics 163 Index 189 Introduction 163 Petrographic examination and complementary techniques 163 Clay brick 164 Terracotta 166 Ceramic tile 168 Architectural glass 170 5 PREFACE When I embarked upon my career as a construction of an atlas of high-quality colour photomicrographs of materials petrographer I found that there were no specific geomaterials, along with explanations of their books available to help me learn the trade. Instead, like petrographic properties and how to interpret them. An many others my knowledge was gained directly from an introductory chapter provides an overview of experienced expert who guided and supervised my early geomaterials practice and a state-of-the-art review of work. I have since been fortunate enough to have petrographic techniques. Each of the subsequent chapters enjoyed a broad range of industrial and research covers a different group of construction materials and experience that has enabled me to compile this includes an explanation of their history, manufacture, guidebook, the process of which has taken 12 years. and use in construction. The length of each of the By providing the first comprehensive guide to the individual materials chapters reflects the relative petrography of geomaterials I have attempted to make importance of the material as an area of commercial the specialized knowledge of the petrographer available petrographic study. to all. It is intended not only for microscopists but for As a discipline, construction materials petrography is anyone with an interest in modern and historic relatively young and dynamic. I intend to update this construction materials from the fields of geology, book at regular intervals to reflect the growth in architecture, surveying, engineering, construction, knowledge and changes to the state of practice. I would archaeology, conservation, materials science, and welcome any contributions and case study examples to forensic science. The format of the book is a combination be considered for inclusion in subsequent editions. ACKNOWLEDGEMENTS AUTHOR PROFILE I wish to express my gratitude to Barry Hunt of IBIS Ltd, Jeremy Ingham is a Consulting Geomaterials Engineer Mike Eden of Geomaterials Research Services Ltd, and who provides consultancy and investigation services for Kate McHardy of Oxford Cryosystems Ltd for generously construction projects worldwide, involving materials contributing photomicrographs for inclusion in this technology, forensic engineering, and asset management book. I acknowledge with thanks the following planning. Commissions range from preconstruction companies who gave permission for me to use advice, quality control during construction, condition photographs of their products: Concrete Experts surveys and remediation of existing structures, failure International ApS, Leica Microsystems GmbH, and investigations, and expert witness services. Logitech Ltd. As a student he gained a BTEC HND in Geological Technology, a BSc in Geology, and an MSc in Geomaterials. His experience of construction materials petrography started with 3 years of working as a geological laboratory technician, which gave him a thorough grounding in the practical aspects of petrography. Next followed a decade spent working as a petrographer, investigating a wide range of modern and historic construction materials. During this time he was responsible for commissioning and managing petrographic facilities and training staff in petrographic methods. Since then he has acted as a consultant, both for new construction projects and conservation of historic buildings. An accomplished microscopist, he is both a Fellow of the Royal Microscopical Society and holder of the Diploma of the Royal Microscopical Society. He is Chairman of the Concrete Society’s Petrography Working Group and a member of the Geological Society's Applied Petrography Group. Contact: www.jeremyingham.com 6 ABBREVIATIONS AAC autoclaved aerated concrete AAR alkali–aggregate reaction AAS atomic absorption spectroscopy ACR alkali–carbonate reaction ASR alkali–silica reaction ASTM American standards CEN Comité Européen de Normalisation CSF condensed silica fume C-S-H calcium silicate hydrates DEF delayed ettringite formation DSC differential scanning calorimetry DTA differential thermal analysis EDS energy dispersive X-ray spectroscopy EN European standards EPM electron probe microanalysis ESEM environmental scanning electron microscopy FESEM field emission scanning electron microscopy FGD flue gas desulfurization GGBS ground granulated blastfurnace slag HAC high-alumina cement HF hydrofluoric acid ICP-AES inductively coupled plasma atomic emission spectroscopy KOH potassium hydroxide NR (in captions) normal reflected light PCD popcorn calcite deposition PFA pulverized fuel ash PPR (in captions) plane-polarized reflected light PPT (in captions) plane-polarized transmitted light PVA polyvinyl acetate PVC polyvinyl chloride PVDC polyvinylidene dichloride RAAC reinforced autoclaved aerated concrete SBR styrene butadiene rubber SEM scanning electron microscopy SMA stone mastic asphalt SRPC sulfate-resisting Portland cement TGA thermogravimetric analysis TSA thaumasite form of sulfate attack UV (in captions) reflected fluorescent light W/C water/cement ratio XPR (in captions) cross-polarized reflected light XPT (in captions) cross-polarized transmitted light XRD X-ray diffraction XRF X-ray fluorescence 1 Introduction 7 OVERVIEW OF GEOMATERIALS AND cement, which can be mixed with sand and water to make PETROGRAPHY mortar for bonding masonry units. Gypsum is heated to produce plaster and plasterboard. Large stone blocks are Geomaterials are defined as ‘processed or unprocessed used as armourstone protection for coastlines and soils, rocks or minerals used in the construction of riverbanks. Aggregates from crushed rock are used for buildings or structures, including man-made construction roadstone, either loose or in layers bound by bitumen, as materials manufactured from soils, rocks or minerals’ macadam and asphalt. Both crushed rock and natural (Fookes, 1991). The definition deliberately includes man- gravel aggregates are mixed with Portland cement and made materials such as bricks or cement but excludes water to produce concrete. Aggregates of all origins are allied engineering materials whose manufacturing is more used as fill materials for earthworks. Pure silica sands are extensive, such as steel and synthetic paints. melted and cast into glass for windows and other Geologically derived materials have been used in architectural elements. Clay soils can be used to make sun- construction for much of human history and, being dried or kiln-fired bricks for masonry construction, geologically common, are available worldwide. Strong architectural terracotta, and ceramic tiles. Figure 1provides rocks provide dimension stone for masonry, cladding, and a summary of the main resources used for bulk flooring, while thinly bedded or cleavable rocks are suitable construction, showing the links between the various raw for roofing. Limestone can be calcined to produce lime or materials, the finished products, and their uses. Cut or Kilned or 1 Raw materials crushed product fired product Mixture Use ed Slate Sea and river olidatocks Sandstone Armourstone defences nsr + bitumen Co Igneous Crushed rock = asphalt Surfacing rock Lime binders c Limestone Foundation fill Mono-mineralirocks Gypsum Dimension stone Gypsum plaster Buildings Mortar, render, Clay or Portland cement screed Mudocks shale Bricks and clay Structures r Brick clay products d e onsolidatrocks GSraanvdel Glass Concrete Cproondcurecttes c n U 1Flow chart showing the relationships between the main geological construction materials and their uses (adapted from Woodcock, 1994). 8 Introduction The economic importance of geomaterials and their the full lifecycle of built assets with tasks typically contribution to the global construction industry cannot comprising: be overestimated. For example, the ex-works value of • Location of new construction material resources. raw materials production for the construction industry • Evaluation of materials proposed for use in in Britain alone was estimated as being £2,105,000,000 construction. in 2004 (Taylor et al., 2006). Table 1 lists the quantities • Routine quality control testing and monitoring of different geomaterials produced for construction in the during construction. British Isles. • Investigation of deterioration during service. Testing of construction materials to ensure that they • Screening existing structures for potential problems. are fit for purpose has been an essential part of the • Monitoring repair and restoration programmes. construction process since the early 19th century. The • Expert witness service. second half of the 19th century saw the emergence of independent materials testing companies (Doran & Clients of the geomaterials engineer may include Cockerton, 2006). Since the 1920s there has been a architects, engineers, specifiers, surveyors, commercial growing cooperation between civil engineers and property owners/managers, domestic property owners, geologists to develop the knowledge of geomaterials in manufacturers, contractors, and government agencies. the construction industry. During the last 40 years, Petrographic examination is one of the most powerful geomaterials practice has evolved into a discipline in its investigative tools available to the geomaterials engineer. own right. Today, geomaterials practitioners apply It involves using the polarizing microscope to examine thin geological and materials engineering knowledge to sections or polished surfaces of samples, in the same way construction and civil engineering projects, ranging from that geologists examine rock samples. This may be new building and infrastructure developments through supplemented by various other microscopical techniques, to monitoring, maintenance, refurbishment, and chemical analysis, and simple physical tests. First used for conservation of existing structures. They are involved in examination of rock in 1849, petrography was soon applied Table 1Production of construction geomaterials in the United Kingdom, 2004 (Taylor et al., 2006) Material Type Quantity Building stone Igneous rock 189,000 tonnes Sandstone 439,000 tonnes Limestone 226,000 tonnes Dolomite 8,000 tonnes Slate 763,000 tonnes Aggregate Concrete aggregate 81,293,000 tonnes Roadstone 47,768,000 tonnes Rail ballast 3,630,000 tonnes Armourstone 333,000 tonnes Construction fill 39,313,000 tonnes For glass making 5,011,000 tonnes Cement Finished product 11,405,000 tonnes Concrete Ready-mixed 22,856,000 cubic metres Brick Clay brick 2,707,000,000 bricks Gypsum For plaster products 1,686,000 tonnes Overview of geomaterials and petrography 9 to other construction materials. The technique requires • The examinations should be conducted using very specialist equipment and operators with appropriate high-quality optical microscopes. qualifications and petrographic experience. Through the • It should have good in-house specimen preparation microscope the petrographer can determine the composi - facilities. tion of geomaterials, assess their quality, and investigate • An extensive collection of petrographic specimens the causes and extent of deterioration. Photographs taken should be available for the petrographers’ reference. through the microscope (photomicrog raphs) provide • There should be access to complementary compelling evidence for clients. Around the world, tens of microscopical and chemical analysis techniques. thousands of petrographic examinations are performed on construction materials each year. The main requirements Commercially, petrographic examination is conducted in for a commercial geomaterials petrography laboratory are: accordance with the published standards listed in Table 2. • It must led by an experienced Standard methods have still to be agreed for certain types petrographer/geomaterials practitioner. of material and in certain geographic regions. Table 2Current standards for the petrographic examination of geomaterials Material British standard European standard American standard Building stone Use European standard EN 12407 1 WK26092 Roofing slate Use European standard EN 12326-2 3 None* Rock None, use ISRM 1977 4and BS 5930 5 Armourstone Use European standard Use EN 932-3 6 None* Aggregate BS 812-104 7 EN 932-3 6 ASTM C295 8 Concrete None – use American standard None – use American standard ASTM C856 9 Mortar None – use American standard None – use American standard ASTM C1324 10 Bricks and ceramics None* None* None* Bituminous mixtures None* None* None* * Adapt the techniques described in other petrography standards as appropriate. 1 British Standards Institution (2007). Natural Stone Test Methods – Petrographic Examination:BS EN 12407. BSI, London. 2 ASTM International (2006). New Standard Guide for Petrographic Examination of Dimension Stone.WK2609 (proposed new standard in draft form and under development). ASTM International, Philadelphia. 3 British Standards Institution (2000). Slate and Stone Products for Discontinuous Roofing and Cladding – Part 2: Methods of Test:BS EN 12326-2. BSI, London. 4 International Society for Rock Mechanics (ISRM) (1977). Rock Characterisation, Testing and Monitoring. Suggested Method for the Petrographic Description of Rock.Pergamon Press, Oxford. 5 British Standards Institution (1999). Code of Practice for Site Investigations:BS 5930. BSI, London. 6 British Standards Institution (1997). Tests for General Properties of Aggregates – Part 3: Procedure and Terminology for Simplified Petrographic Description:BS EN 932-3. BSI, London. 7 British Standards Institution (1994). Testing Aggregates – Part 104: Method for Qualitative and Quantitative Petrographic Examination of Aggregates:BS 812. BSI, London. 8 ASTM International (2008). Standard Guide for Petrographic Examination of Aggregates for Concrete.ASTM C295-08. ASTM International, Philadelphia. 9 ASTM International (2004). Standard Practice for the Petrographic Examination of Hardened Concrete.ASTM C856-04. ASTM International, Philadelphia. 10ASTM International (2005). Standard Test Method for Examination and Analysis of Hardened Masonry Mortar.ASTM C1324-05. ASTM International, Philadelphia.