Yig. 1.1. Engineering geological map of the solid or bedrock of the UK Drawn at an original scale of 1 : 2 000 000, and reproduced here at approximately 1 : 3 500 000 r Bickmore & Shaw, 1963; Map of Predominant Types of Rock) (from Dearman 1991).

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1. Introduct ion

1.1. Stone

The word 'stone' has several meanings which, for understanding, have generally to be evaluated in their context and it is therefore necessary to highlight this and to define how 'stone' is used in this Book. The Concise Oxford Dictionary defines stone as 'Piece of rock of any shape usu. detached from earth's crust and of no great size, esp. a pebble, a cobble, or a single piece used or usable in building or road-making or a missile'; in Chambers Dictionary of Science and Technology stone is 'A jewel'; in the popular Penguin Dictionary of Geology, it is stated that 'the word 'stone' is admissible only in combinations such as limestone, sandstone, etc. or where it is used as the name for extracted m a t e r i a l - building stone, road stone. It should not be used as a synonym for rock or pebble'.

In the Penguin Dictionary of Civil Engineering, stone is said to be synonymous with coarse aggregate which is defined as that material which stays on a sieve of 5 mm square opening when used in concrete, or on a sieve of 3 mm square opening when used in bituminous material. Aggregates are those stones, i.e. particles of rock which are brought together in a bound or unbound condition to form part of the whole of an engineering building structure. In civil engineering, normal use for aggregates is in concrete or roadstone (Smith & Collis 1993).

In this Book, 'stone' is rock which is used, other than as concrete or roadstone aggregate, in the construction of buildings or structures made by man. In order to give emphasis and clarity, the word 'stone' can be supple- mented with further descriptive terms, for example dressed stone, dimension stone, gabion stone, armour stone, to illustrate the use to which it has been put or the method used to modify its characteristics to be suitable for the construction use.

Stone has been fashioned by man since Palaeolithic times. Ancient stone buildings demonstrate its durability and many buildings and structures owe their attractive- ness to the stone selected for its colour, decorative and ornamental appearance, as well as its strength. No civilisation appears to pay much attention to the cost where its prestigious buildings are concerned. The Pyramids, Roman temples and baths and Norman castles are examples of symbols of prestige where no expense was spared to make a maximum impression on the general populace.

Britain is potentially well endowed with stone and a glance at Fig. 1.1 is sufficient to show that it has a variety of rock which it is difficult to match elsewhere in a similar small area. The local buildings reflect this wide variety of stone and Britain has a long tradition of building in stone. However, this book is not solely about British

stone and, where appropriate because of differences in practice, circumstance or environment, the different uses and performance of stone overseas are discussed.

1.1.1. Production statistics

Table 1.1 shows recent production statistics for the principal minerals and rocks in the United Kingdom, including England, Wales and Scotland as separate totals, and the principal rock types extracted in U K which are given with further subdivisions by end use.

Statistical data on stone is notoriously difficult to correlate owing to changes in annual production, changes to classification of materials and end-uses, incomplete records and erroneous data. Nevertheless, Table 1.1 can be used to obtain an appreciation of the order of magnitude of production of rock types for construction and other uses.

As can be seen, in general England extracts by far the largest amount of rock and also, of that, building stone is a relatively small proportion of which the most is limestone. From the table, 'building stone' is approxi- mately 2 million tonnes per annum. Rock used as aggre- gate is by far the largest use, particularly as roadstone, approximately 100 million tonnes per annum. 'Other constructional uses' presumably including general fill, rock fill and armour stone are, as can be seen, also considerably larger in amount than building stone.

Table 1.2 presents information for other countries and is based on 'quarry production' and may well contain data on aggregates as well as dimension stone.

Obtaining detailed information for many countries is difficult, if not impossible, and Table 1.2 has many omissions. It shows 'marble' (loosely interpreted as polishable limestones and true marbles), granite and all 'other stone', quarried for stone products. The pre- eminence of Italy as a stone producer stands out; by comparison with Italy and several other countries, Britain is not a large producer.

As an example of the problems of correlating statistics, it can be seen that the estimate for the U K in Table 1.2 (1.1 million) agrees only very approximately with Table 1.1 (1.86 million).

1.1.2. A future for building stone

The use of stone is currently rising for both local materials and imported materials. At present it seems that the growth in new stone for building is in granite and marble - possibly because these are generally higher value materials and have a greater range of textures and colours. In some areas there is also a growth in

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Table 1.1. Mineral production in Great Britain in 1991 excluding coal gypsum salt and potash (in '000 of tonnes)

Mineral England Wales Scotland Great Mineral England Wales Scotland Great Britain Britain

Sand and Gravel (a) Igneous rock Sand of which for: building stone 22 11 94 127 for: coat ing 3 517 - 4 654 coated roadstone 6 794 1 087 3 074 10 955

other uses (excl. fill) 10854 266 1299 12419 uncoated roadstone 7407 992 8236 16635 concret ing sand 22 330 831 5 644 26 805 railway ballast 1 711 248 361 2 320

Gravel of which concrete aggregate 1 270 168 1 513 2 951 for: coat ing 356 - 135 490 other construct ional 5 770 777 6 298 12 846

concrete aggregate 19 843 321 2 824 22 988 uses other uses (excl. fill) 2210 - 2569 other uses 151 12 12 175

Sand gravel hoggin Total 23 126 3 294 19 588 46 008 for: fill 12308 221 8025 15554

Total 71417 1836 12 226 85 479 Sandstone for: building stone 227 9 - (130)

coated roadstone 1 502 447 424 2 373 Limestone (b) uncoated roadstone 3 457 532 302 4 290 for: building stone 1 407 22 - 1 430 railway ballast - - - 206

coated roads tone 11 226 - 13 060 concrete aggregate 376 49 165 590 uncoa ted roads tone 31 691 7918 214 39823 other construct ional 4 143 431 605 5 179 railway ballast 9 - 291 uses concrete aggregate 9 089 - 11 665 other uses . . . . other construct ional 19 560 4 821 446 24 827 Total 9 907 1 466 1 555 12 928

uses agricultural use 836 - 1 206 iron and steel - 2 206 cement - - 8 903 glassmaking 231 - 231 asphalt fillers (c) - 5 393 other fillers (c) - 5 910 other uses - 2 824

Total 8 6 7 6 2 18 986 2 0 1 8 107 767

Common clay and shale for: bricks pipes and tiles 8 365 315 361 9042

cement 50 - 2 626 lightweight aggregate 7 construct ional use 909 72 - - other uses - - -

Total 11 916 436 686 13 038

Fireclay Dolomite for: bricks pipes and tiles 306 475 for: building stone 70 - 70 refractory use - (285)

coated roads tone other uses (15) uncoated roads tone 9 391 Total 657 - 867 railway ballast concrete aggregate - - 1 994 Special sands other construct ional 2 897 - 3 435 for: foundry use 1 556

uses o f which naturally 174 16 190 agricultural use - 2 096 bonded other non- 1 520 glass manufacture 1 692

construct ional uses other industrial uses 854 16 91 953 Total 16 602 19 454 Total 3 651 16 553 4 201

Slate Chalk for: roofing and - 53 for: cement 7 057 7 057 d a m p - p r o o f

construct ional use 1 036 1 036 courses agricultural use 547 547 architectural and - 14 fillers powders - - (330) cladding uses

whitings powder and granules - 51 other uses - (920) fill and other uses . . . . 242

Total 10 317 - - 10 317 Total - - - 360

(a) Excluding marine-dredged. (b) Including dolomite used for construct ional uses. (c) Asphal t filler includes as mine dust; other fillers include powders and whitings e.g. in animal feed polymers paint paper and

pharmaceuticals .

Figures in brackets are for 1985 where 1991 data was unavailable. Source: Central Statistical Office ('91) and Business Statistics office ('85).

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INI 'RODUCI ION 3

Table 1.2. Production o f Dimension Stone in other Countries (tonnes)

Country Marble Granite Other Total stone

Argentina 16 500 54 000 20 100 90 600 Australia 200 7 900 27 290 35 530 Austria 14000 8 100 22 100 Belgium 364 000 Brazil 1 673 400 Bulgaria 47 400 - 85 300 132 700 Canada 240 500 240 500 China 678 000 1 867000 - 2 545 000 France 634000 384200 nd/na 1018 300 Germany 215 900 - - 215 900 Japan 64 300 188 500 252 800 Greece 2 250 000 - - 2 250 000 India 1966400 989 500 - 2955 900 Indonesia 158 000 65 000 - 223 000 Italy 4 800 000 1 100 000 1 346 000 7 246 000 Korea 65000 1 380000 - 1445000 Mexico 712 000 - 712 000 Philippines 712 200 - - 712 200 Portugal 962000 182000 - 1 114000 Saudi Arabia - 154 300 398 000 552 300 Spain 2000 000 980000 - 2 980 000 South Africa 17 200 574 800 26 400 618 400 Taiwan 280 000 - - 280 000 Thailand 87 000 91 750 - 178 750 Turkey 65 000 - - 65 000 United 1 100 000

Kingdom United States 29000 615000 375000 1 019000

of America Venezuela 24150 43 700 3 600 71450

used in more innovat ive ways. This will include the use of stone in composi te materials, for example 's tone veneer cladding' . It is also likely that the p roduc t ion industry will cont inue to undergo modern iza t ion and development changes and become d rawn into debates on the envi ronmenta l impact of quarries and processing plants. In the U K the extension and deve lopment of quarries is a l ready subject to tight controls and, as m a n y quarries are in areas that are designated as being of outs tanding natura l beauty, envi ronmenta l constraints are likely to become more restrictive. It is possible that this could increase the volume of imports as o ther countries, par t icular ly f rom those where the indust ry is still developing and expanding, may have less rigid controls on heal th and safety, and the environment .

1.1.2.1. Europe In addi t ion to the development of the wor ldwide marke t for stone there has been the deve lopment of s tandards for the single Eu ropean Market . These s tandards con- tain m a n d a t o r y and regula tory parts that at present cover specification and testing of stone for construct ion. It is hoped that there will also be guidance on the design and installation for the many uses of stone but these are unlikely to be ready for many years. The new s tandards seem to show a t rend towards the use of pe r fo rmance s tandards and increasingly for the pe r fo rmance of p re formed units ra ther than materials. Provided that the new s tandards are not too onerous then they should help to p romote the use of stone in Europe.

(Data Source: Stone Statistics 1991-1995 Internazionale Marmi & Macchine Correra S.p.A. 1996).

t radi t ional ly used local stones where new construct ions are restricted to materials that ma tch existing building.

On a wor ld scale the stone sector may be in danger of expanding too far and too rapidly. Any visit to an in ternat ional stone exhibit ion reveals a bewildering array of materials f rom many countries, the latter including a large number classed as developing. The stone f rom newer areas is often very competi t ively priced and consequent ly often sells well - but it is also a novel mater ia l with little k n o w n about its performance. As a result there is often resistance f rom architects and specifiers who seem to prefer materials with which they are experienced or for which they can obtain test results in an unders tandable form. It is impor tan t that all countries are able to p roduce informat ion to c o m m o n s tandards - whether ISO or C E N - as this will help to p romote the use of stone and create a feeling of confidence amongs t architects, engineers and specifiers.

Wor ldwide , it seems that the natura l stone p roduc t ion industry has an assured future with more stone being

1.2. Objectives of the Working Party

The objectives of the Work ing Par ty Repor t upon which this book is based were:

�9 To review the influence of the occurrence, mineral composi t ion and geological history on the engineering properties of stone used in construct ion. N o account would be taken of artificial stone.

�9 To consider stone essentially in terms of its intrinsic propert ies as a geological and engineering material , recognising that, depending on the circumstance, the engineering per fo rmance of the stone can be a funct ion of the design as well as the local environ- ment. However , detai led considera t ion of design was not seen as a role of the Report .

�9 To concentra te main ly on stone p roduced and used in the Uni ted K i n g d o m but to refer wherever possible to stone in other countries, par t icular ly but not exclu- sively, where British specification, design and con- struction practices are, or are likely to be, followed.

�9 To review the different geological si tuations in which the sources of stone can occur, no a t tempt being made to quant i fy U K or other nat ional resources

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4 IN 1RODUC 1 tON

or to forecast trends in supply and demand. It would be beyond the scope of the publication to deal in any detail with the many commercial and environ- mental factors which influence the practical choice of stone.

�9 To take into account the increasing emphasis being placed on the planning of mineral extraction, quality assurance and control, and protection for the envi- ronment, while recognizing that the Report would not have the intention nor enough space to permit extended treatment of these subjects.

�9 To identify relevant Standards and other Specifica- tions and Codes of Practice and, where appropriate, to summarize and discuss some of the currently accepted limits.

�9 To explore some of the problems commonly encoun- tered in applying Specifications and Codes, for example, where limits for different properties might be incompatible with each other, or the Specification of Properties which would tend to be mutually exclusive for geological or other reasons, or Specifica- tions which might not be appropriate to the available materials in the local environment. It would not be the intention to propose alteration or alternative specifi- cation so much as to assist the reader in the inter- pretation and implementation of selected portions of existing Standards and Codes of Practice, and in the development of Specifications where these are not readily available.

�9 To provide an authoritative, comprehensive and as up-to-date as possible presentation of all aspects of stone and rock in construction in one document.

To achieve the maximum possible breadth and balance of the Report, it was intended that advice and criticism be canvassed from a range of individual specialists, professional institutions, learned societies, industrial associations and research bodies.

As such, it must be made clear that the concepts and techniques described in the Report are drawn from a wide scientific spectrum in which geologists, chemists, other scientists, engineers, architects and other disci- plines all collaborate with those involved in the investigation, extraction, processing, design, building and maintenance of structures using stone. As such, a report which links such diverse fields in a common theme will inevitably be considered by persons of widely differing vocational backgrounds. Consequently, basic material which is included in one section might be con- sidered by an expert in that particular field to be oversimplified. However, it is thought that this approach is justified in order to serve a wide readership and hoped that any elementary facts might assume a new signifi- cance when presented in relation to the central theme.

It was further recognized that, although the objectives focused on specific areas within a wide field, difficulties would remain with Standards and Codes of Practice

being under more or less constant revision throughout the world, especially in the European Union; and with the rapid progress of experience and research in the subject making it virtually impossible for a review to be up to date and wholly comprehensive in this respect.

1.3. The Working Party and the Report

The Working Party was drawn widely from experts in their fields to represent all principal aspects of the industry, together with users and researchers. Similarly, chapter reviewers (i.e. corresponding members) were also ehosen from the same broad spectrum of those asso- ciated with stone. Individuals are listed after the Preface.

Having made the decision to include stone used in heavy civil engineering works in addition to that used in traditional building it was decided, after some deliber- ation, to structure the book in two parts: the first to deal with aspects common to stone, including geology, exca- vation, winning and processing, and the second to be specifically concerned in each chapter with the various uses of stone in construction.

The chapter on the geology is written, with difficulty, to be as palatable as possible for non-geologists, yet to give a sufficient level of expertise for geological readers to be useful for reference. Special text boxes of intro- ductory geology have been included in this chapter for readers with no or little geological knowledge. Rock classification and composition, and rock structure, two important topics for the stone industry, especially in selection, winning and processing, are highlighted in this chapter. This chapter, in common with the others, is cross-referenced where appropriate to other chapters and has references and bibliography to lead readers, should they wish, to further information sources.

The exploration and assessment chapters are closely related and review the qualification and quantification of potential usable rock resources and their assessment for economic extraction. The following chapters on the principles and practices in the extraction and processing of stone were considered essential for the balance of the Book with emphasis being placed on the influence of geological conditions and the extraction methods employed and, where appropriate, the relationship of geology and extraction to further processing of the rock.

The specific chapters concerned with the uses of stone are essentially self-contained but make necessary cross- reference to the earlier background chapters. A very large amount of rock is used in construction as civil engineer- ing fill, often for dams and highway and railway embankments. The rock fill chapter emphasises the changes which follow from the development of modern, heavy compaction plant, with rock properties of primary importance to the performance being explained and supported by case histories. Armourstone, i.e. rock used for coastal protection and harbour works, is reviewed

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IN IRODUC 1 ION 5

and particular emphasis placed on the demand and selection criteria for suitable material, testing procedures peculiar to armour stone and case studies.

Although stone is historically used as masonry in buildings and civil engineering structures, its modern use tends to be somewhat restricted to masonry facades to frame buildings and various claddings. This change and its consequences are considered in the chapter on natural stone for building and civil engineering, with attention being paid to particular factors which need to be considered when using thinner stone slabs for cladding. Testing regimes for the various uses of stone are described. The last chapter, based largely on practical experience, concerns stone repair and restoration, includ- ing the explanation of the mechanisms by which stone deteriorates in service together with details on modern approaches to cleaning and remedial action.

The book includes three appendices. The first is a glossary of terms used in the various parts of the book and the second contains a compilation of test methods which are referred to in the main text. This has been included to give an outline of procedures which are not readily accessible in nationally standardized tests. The third is a compilation of the physical and strength properties of stones, together with some explanatory notes. It is most strongly emphasized by the Working Party that data in this appendix should only be used with considerable caution. We have no knowledge of the provenance or reliability of the data assembled for the Appendix. Rocks of identical or similar name and petrological description vary widely in their properties due to fabric and textural differences, state of weathering and/or alteration, small mineralogical differences, differ- ences in induration, cementation, cohesion and grain boundary conditions, microfracturing, stress, together with method of working in the quarry, processing and subsequent history. Therefore, it must not be assumed that similar rocks from different locations will have similar properties: they may or may not. Instead, reliance should be placed on comprehensive sampling and testing and quality control of the individual rock sources.

Attention is drawn to the implications of the use of such terms as 'weathering' and 'weathered rock' through- out the text. Near-surface rock weathers in geological time by subaerial agencies. This weathering slowly changes the rock to a soil, or specifically a residual soil, and long before it reaches this condition the properties of the rock, even when slightly weathered, begin to change (Anon 1990). Many quarries in the UK and around the world work a slightly to moderately weathered rock and, even in an otherwise uniform rock, small changes in weathering, which occur throughout the weathering

profile from the ground surface downwards, will bring about various changes in the properties of the rock. Therefore, the form and influence of the weathering on rock must be taken into consideration in its evaluation and use. Test properties reported are often those of fresh rock whereas delivered rock may be somewhat weath- ered and have different properties. Users and specifiers must be aware of this.

Weathering also occurs in stone when in place in its construction. Such weathering is commonly referred to by architects and engineers and the form and style of weathering, together with the rate of weathering, are important in buildings and other structures, particularly historic buildings. Such weathering occurs in engineer- ing time and does not lead to the development of soil but does disfigure stone in use and hence is a most important topic. Rates and style of such weathering will depend on the original properties of the rock, its method of winning and processing and the environment in which it is placed.

Rock weathering in geological time is discussed mainly in the chapter on geology and stone weathering in engineering time is discussed mainly in the last two chapters on stone in building and civil engineering use and in stone repair and restoration. It is also mentioned in Appendix C.

References

ANON 1990, Tropical Residual Soils. Geological Society Engi- neering Group Working Party Report. Quarterly Journal of Engineering Geology, 23, 1-101.

BICKMORE, D. P. & SHAW, M. A. 1963. The Atlas of Britain and Northern Ireland. Clarendon, Oxford.

COLLOCOTT, T. C. & DOBSON, A. B. (eds) 1975. Chambers Dictionary of Science and Technology, 2, L-Z. Chambers, Edinburgh.

DEARMAN, W. R. 1991. Engineering Geological Mapping. Butterworth Heinemann, Oxford.

SYKES, J. B. (ed.) The Concise Oxford Dictionary of Current English, 6th Edition 1977, University Press, Oxford.

WHITTEN, D. G. A. & BROOKS, J. R. V. 1979. The Penguin Dictionary of Geology. Penguin, Harmondsworth.

SCOTT, J. S. 1991. The Penguin Dictionary of Civil Engineering, 4th Edition Penguin, London.

SMITH, M. R. & COLLIS, L. (eds) 1993. Aggregates." Sand, Gravel and Crushed Rock Aggregates for Construction Purposes (2nd edn). Geological Society, London, Engineering Geol- ogy Special Publication, 1.

Stone Statistics 1991-1995. Internazionale Marmi & Macchine Correra S.p.A. 1996.

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