Industrial Minerals Laboratory Manual - Construction materials

British Geological Survey TECHNICAL REPORT WG/94/12 Mineralogy and Petrology Series

Industrial Minerals Laboratory Manual

CONSTRUCTION MATERIALS D J Harrison and A J Bloodworth

Mincralogy and PctrologyGroup British Geological Survcy Kcyworth Nottinghatn Unitcd Kingdom NG12 5GG

British Geological Survey TECHNICAL REPORT WG/94/12 Mineralogy and Petrology Series


CONSTRUCTION MATERIALS D J Harrison and A J Bloodworth A Report preparedfor the Overseas Development Administration under the ODA/BGS Technology Development and Research Programme, Project 91/1

ODA Classjfication: Subsector: Others Subject: Geoscience Theme: Mineral resources Project title: Minerals for Development Reference number: R554 1 Bibliographic reference: Harrison, D J & Bloodworth, A J Industrial Minerals Laboratory Manual: Construction materials BGS Technical Report WG/94/12 Subject index: Industrial minerals, aggregates, dimension stone, brick clay, laboratory techniques Cover illustration: Close-up of roadstone specimens located on the 'road wheel' in an accelerated polishing machine used to determine polished stone value(PSV). Photo courtesy of ELE International Ltd. 0 NERC 1994

Keyworth, Nottingham, British Geological Survey, 1994

CONTENTS Page

1. INTRODUCTION

1

2. AGGREGATES

4

3. DIMENSION STONE

42

4. BRICK CLAYS

48

REFERENCES

64

STANDARDS

68

APPENDICES: 1.

Petrographic examinationof aggregates

71

2.

Relative densityand water absorption

73

3.

Aggregate impact value( A N )

75

4.

Aggregate crushing value (ACV)

76

5.

Ten per cent fines test

77

6.

Los Angeles abrasion value (LAAV)

78

7.

Aggregate abrasion value (AAV)

79

8.

Polished stone value(PSV)

80

9.

Methylene blue dye absorption

82

10. Porosity and saturation coefficient

83

11. BRE crystallisation test

84

12. Acid immersion test

85

13. Clay liquid limits

86

14. Plastic limitand plasticity index

92

15. Green-to-dry and fired properties

94

Preface Industrial mineral raw materials are essential for economic development. Infrastructure improvement and growthof the manufacturing sector requires a reliable supplyof good quality construction minerals and a wide range of other industrial mineral raw materials. Although many less developed countries have significant potential industrial mineral resources, some continue to import these materials to supply their industries. Indigenous resources may not be exploited (or areexploitedineffectively)becausethey do notmeetindustrial specifications, and facilities and expertise to carry out the necessary evaluation and testwork are unavailable. Unlike metallic and energy minerals, the suitability of industrial minerals generally depends on physical behaviour, as well as on chemical and mineralogical properties. Laboratory evaluation often involves determination of a wide range of inter-related properties and must be carried out with knowledge of the requirements of consuming industries. Evaluation may also include investigation of likely processing required to enable the commodity to meet industry specifications. Over the last 10 years, funding from the Overseas Development Administration has enabled the British Geological Survey to provide in the evaluation of their industrial assistance to less developed countries mineral resources. This series of laboratory manuals sets out experience gained during this period. The manuals are intended to be practical bench-top guides for use by organisations suchas Geological Surveys and Mines Departments and are not exhaustive in their coverage of every test and specification. The following manuals have been published to date: Limestone Flake Graphite Diatomite Kaolin Bentonite Construction Materials A complementary series of Exploration Guides is also being produced. These are intended to provide ideas and advice for geoscientists involved in the identification and field evaluation of industrial minerals in the developing world. The following guide has been published to date:

Biogenic SedimentaryRocks A J Bloodworth Series Editor

D J Morgan Project Manager

..

.

1 ~~~~~~~


Constructionmaterials

1.

INTRODUCTION

Stone, brick and cement have been used for construction since ancient times, although the relative importance of these resources has changed with time. Many ancient civilisations developed the use of natural stone to a fineart, and dimension stonestill occupies an important placein architecture, particularlyin the construction of prestigeous buildings. The Greeks andRomans discovered that a relatively strong and durable mortar couldbe made by mixing certain types of volcanicorash calcined claywith lime. Although ‘Roman’ or ‘pozzolanic’ cement was it was not until widely-used as mortar for dimension stone and bricks, in 1824 that concretes could be the development of Portland Cement manufactured with sufficient strength to allow the construction of roads, all sizes. Concrete is produced by the bridges and buildings of in a cement matrix, and incorporation of stone particles (aggregate) demand for concreting aggregates (crushed rock, sand and gravel) continues to rise throughout the world. Aggregates are also widely used in road construction. Roads are usually built with a sub-base of coarse aggregate andsurfaced by concrete or asphalt (sand/bitumen mixture). A surface ‘wearing course’is often added byrolling crushed rock chippings into the asphalt. The demand for aggregates to be in used modem road systemsis enormous; in most countries large volumes of crushed rock, as well as naturally-occurring sand and gravel, are used in road construction and concrete production. amongst the most important materials used for Fired clay bricks are construction in less developed countries. The durability, dimensional consistency and relatively low finished-value of bricks ensures that they are utilised foran extremely wide variety of construction purposes. Clay raw materials for brick making come from a wide variety of sources. This is reflected in considerable variationin the mineralogy and chemistry of brick clays.In this respect, clayfor the manufacture of bricks and other structural clay products such as tiles, hollow blocks and sewer pipes differsfrom most industrial minerals. Provided the finished product canbe manufactered economicdly to meet certain specifications, the mineralogy and chemistry of the material are only relevant insofar as they influence fonning fand i n g behaviour.

The construction industry worldwide has a basic need for rocks and minerals and,if society continuesto ask for higher standards of housing, roads and infr’astructure development, then the demands for Mineralogy and Petrology Group, British Geological Survey0 NERC 1994

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Construction materials

constructional raw materialsw l icontinue to increase. Figure 1 shows a summary of the main natural resources used in construction. This manual is concerned with the necessary procedures and techniques which are required to evaluate the properties of raw materials for potential constructional end-uses. Emphasis is given to the preferred laboratory proceduresfor evaluating specific properties and the manual also outlines the major constructional uses of industrial rocksand minerals. The manualis structured to include separate sections on aggregates, dimension stone and brick clays.

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2.

AGGREGATES

The term 'aggregates' describes a wide variety of materials. These are predominantly crushed rocks or naturalsands and gravels (primary aggregates), although industrial byproducts (such as slag, colliery wastes, fly ash) and recycled waste materials (such as brick, concrete,asphalt) may be used as substitutes (secondary aggregates) for quarried materials. There is no single accepted system for the classification of aggregate is convenient to follow materials based on particle size limits, but it usual industrial useagein separating coarse aggregate (rock particles >5 mm diameter) from fine (Table1).

Table 1. Classification of aggregates by particle size. Size limits

Grain size

Qualification

Classification

CoarSe

Coarseaggregate

Cobble 64mm 16mm Fine 5mm Coarse lmm Sand

Medium aggregateFine

(sand)

0.25mm Fine 0.063mm (silt Fines

and Fines clay)

Both coarse and fine aggregates are used in mass concrete or in road construction, althoughfine aggregate isalso used as building sand, asphalt sand and cable sand.

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2.1

Geological occurrence

There aretwo principal sources of aggregate materials: hard be blasted, crushed and processed to consolidated rocks which must aggregates, and natural sand and gravel deposits which are unconsolidated deposits and require minimal processing.

2.1.I Sand and gravel Sand and gravel (Thurrell,l971; MemtJ992) are naturally occurring particulate deposits. They are mostly relatively young, unconsolidated superficial deposits derived from the redistribution of rock weathering products by water, ice or wind. They are usually alluvial deposits (river channel, terrace or fan deposits) or glacial deposits (morainic, fluvioglacial outwash, periglacial material), although modern marine sands and gravels occur widely on the seafloor of many continental in shelf areas (Harrison, 1992a). Sand and gravels may also occur older consolidated or partially consolidated bedded deposits as conglomerates or pebbly sandstones (Piper, 1982).

2.1.2 Crushed rock aggregates Most hard (‘solid’) rocks are potentially suitable for coarse aggregates. However, demanding specifications of aggregate materials used in road pavements and concrete require that ‘high-quality‘ crushed rock aggregates are used. These are commonly derived from indurated and cemented sedimentary rocks and the tougher, crystalline igneous or metamorphic rocks. Sedimentary rocks Most limestones and dolomites are hard and durable and useful for aggregate. They are common rock types and usually occur in thick beds which are structurally simple and easy to quarry. As a consequence, they are widely extracted for aggregate materials, as well as for cement manufacture (limestone only), and for industrial processes which utilise the chemical propertiesof the stone (Harrison, 1992b).

and Sandstones, gritstones, arkoses (feldspathic sandstones) greywackes (‘impure’ sandstones) aredl commonly used as aggregate materials, although their strength and durability directly depends on the degree of cementation. An example of an assessment survey of sandstone resourcesis provided byAdlam et al. (1984).


6


lgneouci rocks Igneous rocks are widely quarried for crushed rock aggregates. The finer-grained varieties (such as dolerite, basalt or high strength, although large porphry) are often preferred due to their amounts of aggregates are also produced from coarse-grained rocks of these rocks for (such as granites and diorites). The suitability aggregate depends on mineralogy, texture, and degree of alteration. Metamorphic roch The wide rangeof metamorphic rock types is reflected in their variable usefulness as aggregate. Coarse or medium grained, massive, granular rocks such as gneisses, quartzites and marbles generally provide high quality aggregates, whereas foliated and platy rocks suchas schists and phyllites are usually weaker and may be less durable. 2.1.3 Weathering

Weathering processes operating in the tropics andin arid regions may of the rock result in discolouration, decomposition, or disintegration material. Ideally, only fresh, or faintly weathered rock material should be used for aggregate.A classification of weathering grades for rock masses is given in a Geological Society Report (1977). In tropical regions, intense chemical weathering results in clay-rich mantles up to1OOm thick (Fmkes et al., 1971), restricting access to of salts in arid areas may unweathered bedrock. Upward migration cause mechanical disintegration of porous sedimentary rocks. Duricrusts (composed of salts transported via porefluids) may develop of a sedimentary rock mass. In desert regions, in the upper few metres the development ofduricrusts (calcrete or silcrete material) within the sand deposits may themselves form potential aggregate materials, although they are generally extemely variable in composition. In general, the best prospective aggregate sources in arid regions are igneous and metamorphic rocks.

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2.2

Uses andspecifications

A brief summary of the major uses of aggregates withan indication of typical specification requirementsis given below. More detailed descriptions canbe found in Smith and Collis(1993) and Pike(1990). 2.2.1 Roadstone

Crushed rock aggregates and natural gravels and sands are commonly used in road pavement construction.In the UK, the USA and many other countries, roadstone is the largest single end-use of construction aggregates. Modem flexible road pavements consist of a series of discrete layers (Figure2).

wearing course

10-40 mm

BEXXXNIW

40-75 m m

Bedrock Figure 2. Roadpavement

construction layers.

The ‘sub-base’ distributes the load onto the subsoil and forms a working platform for construction. It is overlain by the ‘roadbase’ which is the main load-bearing layer. The surfacing layers consist of a ‘basecourse’ and athin ‘wearing course’. Aggregates used in road pavement constructionmay be unbound, or bound by cementitious or bituminous binders. Unbound layers are usually used for sub-bases but may be used for basesor, in the caseof Mineralogy and PetrologyGroup, British Geological Survey 0 NERC 1994

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minor roads, the whole structure. Unbound aggregates generally perfoxm less well than bound aggregates as pavements (Croney & Croney, 1991) but they have the important advantage of comparatively low cost. The performanceof an aggregate layer in a pavement depends on the mineralogical, physical and mechanical properties of the stone, particle shape andgrading (which maybe affected by processing) and the method of laying the pavement. Aggregates which are used in the loadand impact loads,as well bearing layers should be resistant to crushing as chemical and physical weathering.Good pavement drainageis also essential, a characteristic which is affected both by the aggregate grading, and by the pore size distribution within the aggregate. Aggregates which areused in pavement surfacing are also requiredbeto sound, strong and durable.In addition, they must also be resistant to polishing (for skid resistance) and show resistance to stripping (the aggregate must maintain adhesion with the binder). types, as well as natural gravels and A wide range of crushed rock sands and certain secondary aggregates, are used as roadstone aggregates. Well-cemented sandstones and limestones are generally of high strength,as are most igneous rocks. Foliated metamorphic rocks are generallyof low durability, but non-foliated varieties are extemely hard and tough. Road surfacing aggregates are required to be hard wearing andskid resistant; sandstone or igneous rock aggregates are generally preferred forthis purpose.

Specifications for materials used in road making in the UK are givenin Department of Transport(1991) and in relevant British Standards (such as BS 812,882,594,4987,6543). Guidelines in the USA are provided by the American Society for Testing and Materials (ASTM). 2758,1141) and New Zealand Other countries such as Australia (AS (NZS 3 121) have developed theirown national and local standards for roadstone aggregates. These reflect the materials, climatic and economic constraints of the locality. There areno international standards(ISO) for aggregates, althoughdraft European standards are in preparation by the Committee for European Standardisation (CEN). Some typical specification requirements for roadstone aggregates are given in Table 2.

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Table 2. Typical specification requirements for roadstone aggregates. Particle density (specific gravity) Water absorption(anindicator of porosity) Flakiness index (shape factor) Aggregate impact value(AIV strength test) Aggregate crushing value(ACV strength test) 10% fines value (strength test) Los Angeles abrasion value(LAAV attrition test) Aggregate abrasion value(AAV surface wear test) Polished stone value( PSV skid resistance test) Sulphate soundness test (disintegration by weathering test) ~

~~

~

~

~

~~~~

~~~

Generally >2.65 4%

4 5 (for wearingcourse) 2.5 160 ~0.4 >1.5 >19

-

-le

LD

MD

HD

>110 136 47.5 >0.5

>161 ~3.0 >1.0 >8.0 >10

>0.4

>1.8 >IO

>4.0

>IO

>I40 ~3.0 >1.0 >lo >8

LD - Low density MD - Medium density HD - High density

Mineralogy and Petrology Group, British Geological Survey 0 NERC 1994

A70 ~0.25 >7.2

----

>140 4.75 >1.0 >7.5

>8

>8


3.2

Assessment of dimensionstones

3.2.1 Fieldexploration

The exploration for dimension stones varies from regional reconnaissance of potential sources of a wide variety of rock types of specific deposits or site development through to evaluation investigations. Whatever scaleof approach is applicable, it should include a desk appraisal of available geological data and regional mapping studies to determine the stratigraphy, general lithology and structure of the rock units. Site specific studies should include detailed geological mapping supportedby core drilling. Together, these should aim to evaluate the lithology, thickness, degree of jointing and fracturing and the overall geological consistency of the deposit. Samples should drill cores to represent the be obtainedfiom rock exposures and geological variationswithin the deposit, such as colour, texture, bedding and soundness. The samples can then be sawn into blocksfor polishing and finishing andalso for laboratory testing ASTM to or similar standards. At the quarry development stage or production stage, large, orientated quany blocks will need to be extracted from the to a job potential production area. Each specimen block is then subject specific laboratory testing programme. 3.2.2 Laboratory testing of dimension stones

Dimension stones usedin construction shouldbe durable enough to withstand prevailing climatic and environmental conditions,beand strong enoughto resist structural loading without crumbling or failing. The stone mustalso resist staining. Evaluation procedures for dimension stones should therefore include means of assessing of water absorption. durability, strength and the amount Durability is principally determined by the physical structure of the stone, particularly pore structure (Ross & Butlin, 1989), although mineralogical composition may also influencethis property. Coarsetextured rocks are generally more durable than fine-textured materials. Stone with a highproportion of very fine pores tendsbetoless durable than stone with a coarser poresize distribution. Petrographical examination of the stone (see previous section on aggregates) can give extremely valuable information mineralogy on and microporosity (Sedman & Barlow, 1989). It is recommended that all studies of dimension stones should include the preparation and examination of thin sections. They are inexpensive and quick to prepare, and their detailed Mineralogy and PetrologyGroup, British Geological Suwey 0 NERC 1994

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description provides information on the parameters controlling durability. may also be assessed The pore structure of a potential dimension stone by determination of the porosity and saturation coefficient (the extent to which the poresfill with water with time). These two parameters indicate theamount of watera stone will absorb under natural conditions. The decay of many porous building stones (chiefly limestones and sandstones)is mainly caused by gypsum crystallisation air,water and the stone. The expansion resulting from reaction between which takes place during the precipitation of gypsum causes the stone to break down. The saturation coefficient and porosity be can calculated of data. from the same set

Porosiry The porosityis the volume of the pores within a stone It is measured by expressed as a percentage of the stone’s total volume. vacuum saturationwith water (Price, 1975). 1per cent. The Porosity may be ashigh as 40 per cent or less than value of porosity, however, does not provide information on pore size or on how the pores are distributed within the stone. Petrological this input, although the observations are therefore required for determination of saturation coefficient provides indirect information on pore size.

Saturation coejjicient The saturation coefficient is a measure of the extent to which the pores are filled when a stone absorbs water for a standard time. Values range between about 0.4 to 0.95. A high value (M.8) indicates a stonewith a high proportionof fine pores (i.e. low durability). A detailed procedure for the determination of porosity and saturation coefficientis given in Appendix 10.

Crystallisation test The Building Research Establishment @RE) crystallisation test (Honeybome, 1982) gives a direct measure of degradation by aggressive accelerated weathering causing crystallisation of salts in pores of the stone.A similar test is specified for aggregates in ASTM C88. In brief, the test involves immersion of dry stone cubesin a solution of two hours at a constant temperature. sodium sulphate decahydrate for This is followed by oven drying at controlled humidity 16 forhours. After cooling, the process is repeated for a total of 15 cycles. The Mineralogy and Petrology Group, British Geoiogical Survey 0 NERC 1994

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results are presented as a percentage weight loss and have been used to divide limestones intosix classes of durability. These classes are summarised in Table 17 and range from gradeA (best) to grade F (worst). A detailed procedure is givenin Appendix 11.

Table 17. Durability grades of limestonebuilding Honeyborne, 1982) Limestone durability grade

stones (after % weight loss

(crystallisation test) A

lo0

The BRE crystallisation test requires relatively sophisticated laboratory facilities and is expensive and time-consuming. The results cannot always be interpreted with confidence since the test can prove unreliable. Indeed, the Stone Federation of Great Britain has recently called for the test be to abandoned. However,it is the most widely of porous building stones. Current accepted test for the durability research in the UK is considering procedures to modlfy the test method in order to improve repeatability.At the momentit is recommended that of pore structure be carried out to evaluate additional indirect studies durability. Many sandstones are liable to decay when exposed to polluted (acidic) atmospheres. BRE recommend an acid immersion testfor assessment of sandstone durability.This is a very simple test invoving the by an immersion of the stone in a suphuric acid solution, followed examination of the sample forsigns of decay. A detailed procedureis given in Appendix 12.

American standards A wide range of test methods for characterising the physical properties of dimension stones has been developed by the American Society for Testing and Materials (ASTM) and are widely Mineralogy and Petrology Group, British GeologicalSuwey 0 NERC 1994

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used on an international basis. The tests include bulk specific gravity / water absorptionASTM C97,modulus of ruptureASTM C99 and compressive strengthASTM C170. Other tests include the detexmination of flexural strengthASTM C880 and the abrasion resistance of stone for flooringASTM C241. Detailed procedures for these tests are given in the relevantASTM Standards.

In strength testing the anisotropy of the stone and the orientation of the natural bedding are important factors. The strength of the stone may also vary greatly whenit is wet. The ASTM tests include procedures to quantify these variations. The selection of a dimension stone is therefore a combination of aesthetic appeal, which is to some extent a function of fashion, and physical specifications. The evaluation of stone is only reliableif the samples available for inspection and testing are representative. Although natural stone aisvariable productit is important the variability is kept within limits which are known and understood,


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4. BRICK CLAYS

Fired clay bricks are amongst the most important materials used for construction in developing countries. The durability, dimensional consistency and relatively low finished-value of bricks ensures that they of construction purposesare utilized foran extremely wide variety from low-cost housing and lining of pit latrines to industrial buildings and high-rise office blocks. Brick clays and (to a lesser extent) bricks it is generally considered uneconomic to are low-value materials and transport them over long distances (they are said to have a high ‘placevalue’). Any assessment of their economic potential must therefore take A deposit of high-quality brick clay this overiding factor into account. raw material has little commercial value if it is remote from a market for construction materials. Clay raw material for brick making comes froma wide varietyof sources including bedded mudrock formations, hydrothermally-altered This is reflectedin volcanic rocks, river alluvium and colluvial soils. considerable variationin the mineralogy and chemistry of brick clays.In this respect, clays for the manufacture of bricks and other structural clay products such as tiles, hollow-blocks and sewer pipes differ from most industrial minerals. Provided the finished productbecan manufactured economically to meet certain specifications, the mineralogy and chemistry of the raw material are only relevant insofar as they influence forming and firing behaviour. 4.1 Structural clay products 4.1 .I Bricks

Relatively low-strength bricks suitable for the construction of low-rise housing and similar buildings are known as common bricks or, where used on the outside aof building, facing bricks. These bricks must normally comply to aminimum compressive strength (Table18). Highstrength/ low-porosity engineering bricks are normallyinused loadbearing applications. Standards specified for bricks (such BS as 3921: 1985) generally includea ‘durability’ requirement expressed as frost resistance and soluble salt content. Whilst frost resistance is not relevant in tropical countries, soluble salt content and related will reflect the durability and appearance specifications for efflorescence of bricks in any climate. Soluble salts (such as gypsum) can cause unsightly efflorescence on the surface of bricks and can cause powdering orflaking of the brick in severe cases. Soluble salts from Mineralogy and Petrology Group, British Geological Survey 0 NERC 1994

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bricks can also react with alkaline componentsin mortar to cause disruption of brickwork over time. Table 18. Classification of bricks by compressive strength and water absorption (from BS 3921:1985).

Class

Compressive strength (N/mm2)

Water absorption % by mass

Engineering A Engineering B

>70 >50

4.5

3%)are best avoidedas raw relatively large amounts of organic matter materials for bricks and other structural clay products. Quartz undergoes a phase change 5’73OC at (the alpha-beta inversion). Since this change involves an expansion, the rate of temperature increase in most manufacturing processes is slowed nearthis temperature for bodies containing substantial quartz, as rapid heating will decompose could cause cracking.Any carbonate minerals present to the oxide and carbon dioxide between 600-90O0C.Release of carbon in porosity of the body. dioxide may cause an increase

All the reactionsdesaibed above occur below the conventional firing range of ceramic bodies. Vitrification, or glass formation, may start at any temperature above900°C, depending on the composition of the body. Fluxing materials react with other body constituents with which they are in contact to form liquid, and the proportion of inaeases liquid as the temperature increases. The body contracts due to the formation of liquid (firing shrinkage) and the porosity is reduced If vitrification is allowed togo too far, so much liquidm y be formed that thebody loses shape.

Reaction can occur between particles on heating without formation of a liquid. Such solid-phase reactions are the first step towards densification, evenin cases where solid-phase reaction is followed by the formation ofa liquid. The process is one of mutual diffusion between atoms of touching particles and is known as sintering. As a result of sintering, particles become fewer and larger and pores are eliminated. Strength is developed through interlocking of particles.


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A common crystalline constituent of fired bricks and other clay-based in ceramics is the mineral mullite. This forms by solid-phase reaction alumino-silicates above8OoC along with cristobalite (Grimshaw, 1971). In bricks made from calcium (carbonate)-bearing clays, hightemperature calciumsilicates such as wollastonite and gehlenite may form (Dunham & Mwakaruka, 1984).

Vitrification, sintering, and the formation of new crystalline phases are with the time-temperature dependant. Additional melting, together fonnation of further crystalline components, is encourageda by ‘soak’ period atmaximum temperature. Optimum soak temperatures andtimes for claysof a given composition can be determined using timetemperature-transformation(”)diagrams. A review of the application ofTIT diagrams to the firing of brick clays and other heavy clay products is given in DOE(1993). On cooling,the liquid solidifies to a glass which cements together the unmelted particles and crystals formed during heating, thus giving strength to the fired body. Figure 14 illustrates typical changes in mineralogy in a brick clay during the firing cycle. This ‘cartoon’is taken from Dunham (1992) which provides a useful reviewof the mineralogyof brickmaking.

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‘Acceptable’ forming properties

\

High

wing shrinkage

Low

‘Optimum’ forming properties

0

10

20

30

40

50

60

Plasticity index

Figure 13. Clay‘workability’ chart (fromBain & Highley, 1979). Plasticityindex is used toindicatetheformingproperties of a particular clay. ‘Optimum’ and ‘acceptable’ properties are defined on the chart; lower values are acceptable for stiff extrusion, whilst soft-mud or hand-throwingrequireshigherplasticityindex values. Plasticlimit defines the position on thechart which indicates likely shrinkage on drying.


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Approximate Temperature ("C) 200 400

Raw Material

600 800

1050

800

600

400

200

Brick Quartz

Quartz

Cristobalite IllitelMica

Mullite

Chlorite Kaolinite

K-Feldspar

K-Feldspar

Glass Plagioclase Wollastonite

Plagioclase Calcite

Pyroxene Melilite Anhydrite

Siderite Gypsum Pyrite

Hematite

Fe-oxidelhyd. Organic material

I

Time (hours)

0

Stages

Figure 14. Changes in mineralogy of brickclay on firing(from Dunham, 1992). The firing cycle comprises a 24 hourramp up to the soak temperature which is followed by 12 hours at 1050°C and completedby a 24 hour coolingperiod. Numbered stages comprise (1) dehydration ofclay minerals, gypsum and iron hydroxides; (2) loss of C02, S and (5) melt hydrocarbons; (3) alpha/beta-quartztransition; (4) solid-statemineralreactions; production; ( 6 ) reactions on cooling.



Vin-ificationcurves Although laboratoryfiring can in no way reproduce the conditionsof an industrial kiln, this method does represent a simple method of iden-ng potential f i g problems such as ‘bloating’, melting and excessive refractoriness. Broad classifications of clays can be drawn by comparing thefired properties of cunknowns’ with those of brick clays of proven commercial value. Fired properties are assessed by heating identical clay test pieces over a temperature ment which broadly corresponds to that likely to be encountered in an industrial kiln. Changes in physical properties such as shrinkage, bulk gravity are then plotted against density, porosity and specific temperature to form a series of ‘vitrification cwes’. Test pieces for brick and other structural clays may be by formed extrusion or hand moulding, either in the form of rods or miniature bricks (briquettes). Where large numbers of clay samples are being processed - e.g. in a regional survey of clay resources - there is a need for unifomityof approach and, for efficiency, sample preparation time needs tobe kept to aminimum. Under these circumstances, 15). small-diameter extruded test pieces are probably the best (Figure These canbe formed using a very simple hand-operated extruder (Figure 16). Changes in the physical properties of test pieces are determined by mercury displacement (Figure17) and water absorption. Detailed methods for the determinationfired of properties are given in Appendix 15. Firing of test pieces is preferably carriedinout a temperature-gradient furnace; a normal muffle furnace can be usedthis butprocedure is much less efficientas the furnace hasto be heated separately for each temperature required. Temperature-gradient furnaces may be of two basic types.(1) A chamber where the temperature changes in a linear manner from one end to another (the test piece is then usually a long rod or brick and individual smaller test pieces are cut this fkom at the end of the firing cycle to correspond to the range of temperatures required). (2) A number of separate cells with temperature differences of the order of 30-50°C (Figure 18). This is the most convenient arrangement as it allows firing of a range of test pieces from a number of samples in one operation. Caution must be exercised when attempting to extrapolate results fkom to its likely the small-scale testing of the firing behaviour of a clay behaviour in commercial practice. Firing of a clay body is a dynamic process and the extent of the various reactions occurring at a particular temperature is a function of the heating rate, theofsize the body and the grain size of its components.Of necessity, heating rates used in laboratory firing trials are much faster than those usedin commercial Mineralogy and Petrology Group, British GeologicalSurvey 0 NERC 1994

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practice, so reactions may not reach equilibrium in the laboratory test pieces. However, test pieces usedin laboratory trials are appreciably - compared to clays used in smaller than commercial ceramic bodies and structural ceramics- the grain size is usually much fineq reactions may in these smaller test pieces. To some extent the therefore proceed faster differences in heating rate andsize/heness between test pieces and stillfact remains commercial clay bodies may balance each other but the that laboratory-derived vitrification curves should only be used asan indication of the behaviourof a clay in a commercial process. Whatever methodology is chosen for laboratory temperature-gradient f i g , it is advisable to submit clays used in existing commercial processes to the firing procedures, in this way building upa same preparation and known processes. This ‘library’ of vitrification curves of clays used for approach is especially valuable where regional surveys of clay resources of are being conductedas it enables a preliminary assessment to be made likely uses. The shapeof the curves reflect physical changes within the clay as vitrification reactions (such as point melting and sintering) proceed with increasing temperature.If available manufacturing technology is range relatively unsophisticated, clays which show a long vitrification are generally more valued as raw material for bricks and other structural clayware. These are more able to tolerate temperature variations likely to be encountered in a traditional intermittent-firing industrial kiln whilst still producing bricks which fall within a given range of physical properties. More advanced technology (such as continuous-process tunnel kilns) may be able to tolerate clays with a much narrower kiln temperature and vitrification range by close control over atmosphere, although consistency and quality-control of the feed 4.1.3). A series of material are of paramount importance (see Section vitrlfication curves derived from brick clays which show ofa fired range properties is shown in Figures 19 to 22.

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Figure 15. Testpiecesformedfrom a series of brickclaysfromFiji. Temperaturegradientincreasesfromlefttoright(from 900" to 1250°C).

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n

/

Hand'e

die

Figure 16. Hand-operatedextruderused pieces.

to formbrick


clay test

61


J

Locking screw

Sornple

-

Mercury in beake

Bokmce

r

1

Figure 18. Mercurydisplacementapparatusused to determine volumechanges on firing in brick clay test pieces.


62


Figure 19.

An eight-cell temperature-gradientfurnace.

Mineralogy and Petrology Group, British Geological Survey 0NERC 1994

63

Construction materials 50

40 Shrinkage (volume %)

40 -

s -5

- 30

A

8

0,

30-

0

- 20

v

;20-

Y

-c

- 10

L

G

10-

0 800

!O

I

I

I

900

1000

1100

1200

Temperature ("C)

Figure 20. Vitrification curve from a Lower Cretaceous brick clay fromsouthern England,The relatively narrow vitrification range shownby this materlal IS typical of a mixed-assemblage clay. The r a id increasein porosity andreversal of shrinkage above 1050°C indicates expansion or %loating' of the claybody, probably due tothe presence of organic matter,

+ Shrinkage (volume YO) n

d

Porosity(volume%)

1100

1200

40

a9 0,

-5

30

0 v

0 800

900

1000

Temperature

1300

("C)

Figure 21. Vitrification curvefrom an Upper Carboniferousbrick clay fromthe English Midlands. The relatively slow changes in porosity andshrinkage in this material are typical of thebroad virtification range shown by kaolinitic clays. 50

.r"

40

20

0 0

n

10

0 800

900

1000

1100

1200

1300

Temperature ("C)

Fiure 22. The vitrification curvetakenfrom a potentialbrick clay from Fiji indicates a refatively refractory claywhichshows little change in shrinkage or porosity below 1100°C. This siliceous clay is likely to produce an under-vitr-Xed, relative11 lowstrengthbrlck when firedtotemperatures employed in most brlckmanufacturmg operations (between 1000" and 1100°C). Mineralogy and Petrology Group, British Geological Suwey0 NERC 1994

64


References Adam K A McL, HarrisonD J and WildJ B L (1984) The hard rock resources of the country around Caerphilly, South Wales. Mineral Assessment Report 140. British Geological Survey.

Bain, J A & Highley, D E (1979) Regional appraisal of clay resources a challenge to the clay mineralogist. pp 437-446 in:Proc. Int. Cluy. Conf. 1978, Oxford. British Cement Association (1988) The Diagnosisof Alkali Silica Reaction. Building Research Establishment (1983) The selection of natural building stone.BRE Digest 269. Broch E & Franklin J A,( 1972) The point-load strength test. International Journal of Rock Mechanicsand Mining Science 9. pp 669697. :minimising the risk of Concrete Society (1987) Alkali-silica reaction damage to concrete.Technical Report 30.Concrete Society, London.

of Road Croney D & Croney P (1991) The Design and PerSonnunee Pavements. McGraw-Hill. Deere D U & Miller R P (1966) Engineering classification and index properties for intact rock. Technical ReportNo. AFWL-TR-65-116.Air Force WeaponsLtd Kirkland Air Force Base, New Mexico.

DOE (1993) The application of time-temperature-transformation diagrams to thefiring of heavy clay products.Future Practise R&D ProJiZe 35. Energy Efficiency Office, Department of the Environment, London. Department of Transport (1991)Specification of Highway Works.3. HMSO, London. Dunham, A C (1992) Developmentsin industrial mineralogy: 1. The mineralogy of brick-making. Proc. Yorks. Geol. SOC.49 (2), pp 95104. Dunham, A C & Mwalearukwa, G M (1984) The mineralogyof brickmaking at Broomfleet,North Humberside. Proc. Yorks. Geol. SOC. 44 (4), pp 501-518. Mineralogy and Petrology Group, British Geological Survey 0 NERC 1994

65


Figg J W & Lees T P (1975) Field testing the chloride content of seadredged aggregates. Concrete. September 1975. Fookes P G, DearmanW R & Franklin J A (197 1) Some engineering aspects of rock weathering with field examples from Dartmoor and elsewhere. Quarterly Journalof Engineering Geology, 4. pp 139- 185. Franklin J A (1970) Observations and tests for engineering description and mappingof rocks. Proc. 2nd. Congress of Int. SOC.of Rock Mechanics, Belgrade. 1. pp 1-3. Geological Society Engineering Group Working Party Report (1977) The descriptionof rock masses for engineering purposes. Quart. Jour. Eng. Geol., 10. pp 355-388. Gillot J E & Swenson E G (1969) Mechanism of the alkali-carbonate rock reaction. Quart. Jour. Eng. Geol., 2. pp 7-23. Grimshaw, R W (197 1) The Chemistry and Physicsof Clays. Ernest Benn, London. 1024 pp. Harrison DJ (1983) Geological problems associatedwith the assessment of resources of limestone and sandstone. pp127-137 in: Proc. Extractive Industry Geology Con$ Warwick Univ. Institution of Geologists.

off the Harrison DJ (1992a) The marine sand and gravel resources Humber. British Geological Survey Technical ReportWB/92/1. Hanison DJ (1992b) Industrial Minerals Laboratory Manual: Limestone. British GeologicalSurvey Technical Report WG/92/29. Hawkes J R & Hosking J R (1972) British arenaceousrocksfor skidresistant road suvacings. Report LR 488, Transport and Road Research Laboratory, Crowthome. Highley, D E (1982) Fireclay. Miner. Resour. Consult. Comm. Mineral Dossier 24. HMSO, London. 72 pp. Hills J F & Pettifer G S (1985) The clay mineral contentof various rock Journal of Chemical types compared with the methylene blue value. Technology and Biotechnology. 35A, 4.

Mineralogy and Petrology Group, BritishGeologiml Survey 0 NERC 1994

66

~

~-


Hobbs D W (1988)Alkali-Silica Reaction in Concrete. Thomas Telford, London. Honeyborne D W (1982) The Building Limestonesof France. HMSO, London. Jones F E & Tarleton R D (1958). Reactions between aggregates and cement. National Building Studies Research Paper 25. KMSO, London. Mathers S J (1993) Industrial Minerals Exploration Guide: Biogenic Sedimentary Rocks. British GeologicalSurvey Technical Report WC/93/15. Memtt J W (1992)A summary of British onshore sand and gravel of methods usedin their appraisal. resources and a critical review Engineering Geology, 32. pp 1-9. Pike D C (1980) Standards for Aggregates. Ellis Horwood, London. Piper D P (1982) The conglomerate resources of the Shemood Sandstone Group: Stoke on Trent.Mineral Assessment Report 91. British Geological Survey. Architects Journal, Price C A (1975) Testing porous building stone. 162. pp 337-339. Ramsey D M (1965) Factors influencing Aggregate Impact Value in rock aggregate. Quarry Managers Journal, London. 49. pp 129-134. Ridgway J M (1982) Common Clay and Shale. Miner. Resour. Consult. Comm. Mineral Dossier 22. HMSO, London.164 pp. Ross K D & Butlin R N (1989) Durability Testsfor Building Stone. Building Research Establishment, Watford,UK. Sedman J H F & Barlow S (1989) The durability of the Bath building

stone. pp 82-91in:Proc. Extractive Industry Geology Con$ Birmingham Univ. Institution of Geologists. Smith M R & Collis L (1993) Aggregates. Geological Society Engineering Geology Special Publication 9. Geological Society, London.


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Thurrell R G (197 1) The assessment of mineral resourceswith particular referenceto sand and gravel.Quarry Managers Journal, London, 55. pp 19-25. Wadell H (1933) Sphericityand roundness of rock particles.Journal of Geology, 41. pp 310-331.


68


Standards

British Standards British Standards InstitutionBS 63 (1987). Specification for singlesize aggregates.

BS 402 (1970) Clay plain roofing tiles and fittings.

BS 435 (1975). Dressed natural stone kerbs, channels, quadrants and setts.

BS 594 (1985). Hot rolled asphalt for roads and other paved areas. BS 680 (1975). Roofing Slates. BS 812 (1990). Testing Aggregates.

BS 882 (1983). Aggregates kom natural sources for concrete. BS 1047 (1983). Specification for air-cooled blast furnace slag aggregate for use in concrete.

BS 1199 (1976). Sands for external renderings, internal plastering with lime and Portland cement, and floor screeds. BS 1200 (1984). Specificationsfor building sands from natural sources - sands formortars for plastering and rendering. BS 1377 (1990). Methods of testing soilsfor engineering purposes.

BS 3921 (1985) Specifications for clay bricks BS 4987 (1988). Coated macadam for roads and other paved areas.

BS 6543 (1990). Guide to the use of industrial byproducts and waste materials in building and civil engineering.

BS 5642 (1978). Sills and copings. Department of Transport, (199 1). Specification for highway works. HMSO,London.

Mineralogy and Petrology Group, British Geological Suwey 0 NERC 1994

69


American Standards

American Society for Testing and Materials. ASTM C29 (1989). Unit weight and voidsin aggregate. ASTM C33 (1989). Standard specifications for concrete aggregates. ASTM C40 (1979). Testing for organic impurities in fine aggregates for concrete. ASTM C88 (1983). Test for soundness of aggregates by use of sodium sulphateor magnesium sulphate. ASTM C97 (1977). Test for absorption and bulk specific gravity of natural building stone. ASTM C99 (1976).Test for modulus of rupture of natural building stone. ASTM C127 (1989). Specific gravity and absorption of coarse aggregate. ASTM C128 (1989). Specific gravity and absorption of fine aggregate. ASTM C131(1989). Resistance to abrasion of small-size coarse aggregate by useof the L o s Angeles machine. ASTM C136 (1989). Sieve analysis of fine and coarse aggregates. ASTM C170 (1976).Test methodfor compressive strength of natural building stone ASTM C227 (1989).Test method for potential alkali reactivity of aggregates (chemicalmethod). ASTM C241(1976).Test method for abrasion resistanceof stone subjected to foot traffic. ASTM C295 (1987).Standard practicefor petrographic examination of aggregatesfor concrete. ASTM C503 (1979). Specification for marble building stone (exterior).


70


ASTM C535 (1989). Resistance to abrasion of large-size coarse aggregate by useof the Los Angeles machine. ASTM C568 (1979). Specification for limestone building stone. ASTM C615 (1977). Specification for structural granite. ASTM C616 (1977). Specification for building sandstone. ASTM C629 (1977). Specification for structural slate. ASTM C880 (1978). Test method for flexural strength of natural building stone. ASTM D692 (1988). Specification for coarse aggregate for bituminous paving mixtures. Australian Standards

Standards Association of Australia. AS 1141 (198 1). Methodsfor sampling and testing aggregates. AS 2758 (1985). Aggregates and rock for engineering purposes. Part 1. Concrete aggregates.

New Zealand Standards Standards Association of New Zealand. NZS 3111 (1980). Methods of testfor water and aggregate for concrete.

NZS 3121 (1986). Specification for water and aggregate for concrete. NZS 4407 (199 1). Clay index test.


71

I


Appendix 1: Petrographicexamination

of aggregates

Procedue for qualitative m i n a t i o n 1.

Recordgeneralcharacteristicsoftheaggregatesampleincluding the maximum particle size and distinguish between natural and of processed aggregate. Describe the grading, texture and shape the aggregate particles.

2.Usingabinocularmicroscopeand/orhandlensidentifythemain rock types and estimate the relative proportions of the constituents. Record colour,grain size, degreeof weathering, alteration etc. Procedure for quantitative aamimtion Coarse aggregates(>5 mm) 1.

Sieve the sample into separate size fi-actions using 50 mm, 37.5 mm, 20 mm, 10 mm and 5 mm sieves.

2.

Determinethe mass of each size hction.

3.

Examineeachsize fixtion anddeterminepetrological composition by hand separation and weighing. This will usually of thin sections of selected particles and require the preparation their examination usinga petrogmphical microscope.Thin sections are particularly valuable for investigation ofgrained fine rocks andalteration products. Sufficientthin sections shouldbe examined to understand the nature of the aggregate and to idenhfy any impurities.

4.

Calculatetheoverallcomposition of thetestsample.

NOTE: In certain circumstancesa simpW1ed (and more rapid) of the examination may be appropriate, involving the single assessment >5 mm size fraction.


72


Fine aggregates (e5 m m ) 1.

Sieve the sample into separate size hctions using 5 mm, 2.36 mm and 1.18 mm sieves.

2.

Determine the mass of eachsizefraction.

3.

Examine each size fraction using a binocular microscope and determine petrological composition by hand sorting. Thin sections maybe required for detailed identification. 4 . 1 8 mm material should be assessed by point countingof a thin section where the material is embedded in resin.

4.

Calculatetheoverallcomposition of thetestsample.

The method(in common with most test methods) requires two representative portions to be tested, and theresult is the mean of the two determinations.


73


Appendix 2: Relativedensityandwaterabsorption

Procedurefor coarse aggregate (40 mm to 5 m m ) 1.

Wash the test portions (1 kg sample size) to remove all traces of undersize material.

2.

Immerse each portion in water (in a gas jar) for 24 hours at 15' to 25°C and weigh (massB).

3.

Empty the gas jar, refdl with water and weigh (mass C).

4.

Place aggregate on a dry cloth and allow to surface dry until visible waterfilms are removed. Thisis the saturatedand surface dried (SSD) condition. Weigh the aggregate (mass A).

5.

Place the SSD aggregate in an oven at 100"to 110O C for 24 hours. Cool and weigh (mass D).

Relative density (oven-dried)

=

D A-(B-C)

Relativedensity(saturatedandsurface Apparent relative density

=

dried)=

D D - (B - C)

Water absorption (%) = (A - Dl x 100 D


A A-(B-C)

74


Procedurefor fine aggregate (x5 mm size) 1.

Wash the test portions (c. 500 g sample size) to remove all traces of undersize ((15 pm) material using a75 pm BS test sieve.

2.

Irnmerse each portion in water (in a gas jar) for 24 hours at 15' to 25 "Cand weigh ( mass B).

3.

Empty the gas jar, refill with water and weigh (mass C).

4.

Dry the sample on the 75 pn sieve using a gentle current of warm air from a hair dryer.Stir to ensure d o x m drying until the fine aggregateattains a 'freerunning' (or SSD) condition. Weigh the aggregate (massA),

5.

Place the aggregate on atray in an oven at 100 - 110 O C and dry for 24 hours. Cool and weigh.

The calculations are the same as those given for the coarse aggregate method.



Appendix 3: Aggregate impact value (AIV) An impact testing machine,as specified in BS 812, is required for this test and shouldbe fixed to a concrete block or floor at least 450 mm thick. The test is carried out on 10 - 14 mm sized aggregatein a surface dry condition. 1.

Place sample portion (mass A) in the 102 mm diameter x 50 mm deep hardened steel cup and tamp to a single horizontal layer.

2.

Fix cup f d y to base of impact testing machine.

3.

Subject the sample to 15 blows from the hammer, which has a 100 mm diameter cylindrical headand a total massof 13.5 - 14.1 kg, falling through3813- 6.5 mm.

4.

Remove the crushed aggregate from the cup and detennine the mass of material (mass B) passing a2.36 111133.sieve.

5.

The test result is the mean of two determinations and is reported A lower numerical value indicates a to the nearest whole number. more resistant rock.

Mineralogy and PetrologyGroup, British GeologicalSuwey 0 NERC 7994

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Appendix 4: Aggregatecrushingvalue(ACV) The testis carried out on10-14mm sized surfacedry aggregate and requires a sample size of about 2 kg. 1.

Place the weighed sample (mass A) in three tamped layersin the 150mm diameter hardened steel cylinder and level the surface of the aggregate.

2.

Load the sample(through the ram apparatus)with a force that is increased at auniform rate from0 to 400 kN in 10 minutes.

3.

from the Release theload and remove the crushed material cylinder.

4.

Sieve the material on a 2.36 mm test sieve and weigh the fiaction passing the sieve(mass B).

5.

Repeat the test,using a second sample of the same mass as the first sample. ACV=& A

6.

X 100

The meanof the two results, to the nearest whole number, is the test result. Once again, a lower value indicates a more resistant rock.

NOTE :The shape of aggregate particles affects both the AIV and ACV. Flakiness can introduce differences AinN and ACV of over 30%.The flakiness index(IF) should always be quoted when comparing particular A N ’ S or ACV’s.


77


Appendix 5: Tenpercent

fines test

The ten per cent fines test is made on 10 - 14 mm sized, surfacedry aggregate whichis loaded in the standard ACV apparatus. 1.

The weighed aggregate sample is placed in the steel cylinder to form a100 ~llfn thick horizontalbed (similar to theACV test).

2.

Apply a uniform loading rate to cause total penetration of the plunger (in10 minutes) of approximately 15 rmn (gravels), 20 rmn (crushed rocks) or24 rmn (honeycombed aggregates). If an AIV is available the required loading can be estimated by : using the following formula

Required force (kN) = 4000 AIV

3.

Record the maximum force (x ) to produce the required penetration.

4.

Release the load and remove the crushed material fkom the cylinder.

5.

Sieve the material on a 2.36 mm sieve and weigh the fraction passing the sieve. Express this mass as a percentage of the mass of the test sample. The percentage fines must fall within the range of 7.5 to 12.5. If it does not, repeat and adjust the loading until the percentage fines fall within this range.

6.

Make a repeat test at the same force (to produce percentage fines within the required range).

7.

TheTenpercentfinesvalue

= 14x kN

yT4

where x is themaximum force (kN) and y is the mean percentage fines fromtwo tests atx kN.

8.

Report the result to the nearest 10 kN for forcesof 100 kN or more, orto 5 kN for loadsof less than100 kN.



Appendix 6: bos Angelesabrasionvalue(LAAV) Test procedure(for 10-14 mm sized aggregate) 1.

Wash the aggregateand dry in an oven at 110"C.

2.

Weigh the test sample(5000g) - mass MI- and place in test machine.

3.

Place 11balls weighing 4800 g (+20 -150 g)in the machine.

4.

Replace the coverand rotate for 500 revolutions.

5.

from the cylinderand wet sieve Remove the crushed material using a 1.6mm sieve.

6.

Dry the aggregate retained on the sieve in an oven at 110OC.

7.

Weigh this oversize material(M2). The LAAV = M I - M - ~x 100 Ml where M1 is the mass of the test portion, and M2 is the mass of aggregate retained on the 1.6 mm sieve.

9.

The resultis quoted to the nearest whole number.


79


Appendix 7:

Aggregateabrasionvalue(AAV)

The testis carried out on non-flaky, washed and surface dry 10-14 mm aggregate, of measured relative density. 1.

Two specimens are made for each test. Each specimen consists of at least24 aggregate particles, placed shoulder to shoulder in a single layerin a metal mouldof specified dimensions. The flattest surfaceof the particles should lie on the bottom of the mould.

2.

with fine sand Fill the interstices between the aggregate particles to three quartersof their depth.

3.

Mix resin and hardener andfill the mould to overflowing. Cover with flat plate and clamp.

4.

fiom the When the resin has hardened, remove the specimens moulds, clean,trim and weigh (massA).

5.

Fit each specimeninto the backing trays and placeon the grinding lapin the abrasion machine. Place weights on the specimen to give a total load of 2 kg.

6.

Rotate the lap through 500 revolutions at a speed of to2830 rpm, feeding abrasive silica sand across the specimens.

7.

trays and Remove the specimensh m the machine and backing weigh (mass B). AAV=3(A-B) d where A is the mass of the specimen before abrasion, B is the mass of specimen after abrasion, andd is the SSD relative density of the aggregate.

8.

The meanof the two tests is calculated totwo significant figures. In this test a lower numerical value indictes a more resistant rock. Some typical AAVs for a range of types rock are givenin Table 15. Values in excessof 15 indicate inadequate abrasion resistance and such aggregates would be considered unsuitable for road surfacing( Hawkes and Hosking, 1972).


80


Appendix 8:

Polished stonevalue

(PSV)

The testis carried out on washed and surface dry, non-elongate mm sieve but is retained on a 10-14 aggregate which has passed a 10 mm flake sorting sieve.A PSV control stone is used for calibration of the friction tester. 1.

Four specimens are prepared for each sample, as well four as specimens of the control stone. Each specimen consists35ofto 50 particles, placed shoulder to shoulder in a single layer with their flattest surfaces lying on the bottom of the mould.

2.

between the particles tothree quarters of their Fill the interstices depth with fine sand.

3.

M i x the hardenerwith the resin and fill the mould with the mixed resin.

4.

When the resin has hardened, remove the specimen from the mould, clean andtrim.

5.

Fourteen specimens are polished on polishing the machine during eachrun. Clamp the fourteen specimens round the of the polishing machine. periphery of the road wheel

6.

Rotate the road wheel at 315-325 rpm and bring the specified solid rubber tyre to bear on the surface of the aggregate with a force of 715-735 N. Continuously feed the tyre with corn emery and water for a period of 3 hours.

7.

Remove the specimens from the machine, and thoroughly clean. in water at 18" to 20°C for a periodof 30 Store the specimens minutes to 2 hours.

8.

of the wet specimen by using the Measure the state of the polish in a room kept at 18' to 22OC. friction test apparatus

9.

Rigidly locate the test specimen in the fiction tester and release the horizontal position. Measure the height of the pendulum fiom the upward swingof the pendulum, afterit has traversed the specimen, by thefiction pointer. Note the reading of the pointer to the nearest whole number.

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10.

The test specimens and control stone specimens are testedin this manner five times, and the mean of the last threereadings is recorded for each.

11.

The mean (S) is calculated for eachgroup of four specimens and recorded to the nearest 0.1 unit. Calculate the mean value (C) of to unit. the four control specimens and record 0.1 Calculate thePSV from the following equation; PSV = S + 52.5 - C

12.

Report the PSV to the nearest whole number.


82


Appendix 9:

Methylene blue dye adsorption

The test procedure is derived from Hills and PettZer(1985) and is carried out on small (1g) representative samples passing75 a pm sieve. 1.

Disperse the sample portion in 30 ml of water and titrate by adding 0.5 ml incrementsof methylene blue solution that has been prepared by dissolving 0.1 ofg methylene bluein 100 ml of distilled water.

2.

After each addition, agitate the suspension for one minute.

3.

Using a glassrod remove a dropof suspension on to a filter paper. The drop consists of a dark blue centre and a colourless rim.

4.

Repeat the procedureat intervalsuntil the end pointis reached. This is evidentby the appearance ofa light blue halo of unadsorbed dye between the dark blue centre and the colourless rim.It indicates thatthe sample isno longer capableof further adsorption.

5.

The methylene blue value (MBV) is : MBV = 0.1v M

where V(ml) is the volume of methylene blue solution to reach the end point, and M(g) is the mass of the test portion.


83


Appendix 10:

Porosityandsaturationcoefficient

1.

Dry four small (4-5mm) samples of dimension stone at 103OC (k3OC).

2.

Cool to 2OoCand place in a vacuum desiccator fitted with a funnel to admit water.

3.

Evacuate the desiccator and maintain the vacuum for two hours.

4.

Saturate the samples with water and admitair to restore atmospheric pressure.

5.

Weigh the samplesin water ( W 1 ) and in air (W2).

6.

Dry at 103OC (k3"C) for 16 hours, cool and weigh(WO).

7.

Immerse the samplesin water at 15-2OoC for 24 hours, remove and weigh (W3).

8.

Porosity (P) is calculated from:

P = WFWO-

x 100%

wi-w;

9.

The saturation coeffecient ( S ) is Calculated from: S = W3-Wn

W2-WO


84


Appendix 11: BRE crystallisation test 1.

Make up sodium sulphate solution (dissolve 1400 g sodium sulphate decahydrate[NazSO4.1OH20] in 8.6 litres deionised water at 20°C W.5"C).

2.

Prepare four to six 4 cm cubesof stone usinga suitable saw.

3.

Wash anddry at 103°C(floc).

4.

Allow to coolin a dessicator to 20°C (floc).

5.

Weigh cubes toB.01 g (Wo).

6.

Label and weigh again(W1).

7.

Place each cubein a 250 ml beaker and coverwith sodium sulphate solution to a depth of 8 mm. Leave for two hours, maintaining temperature at 20°C (fl.5"C).

8.

Remove cubes from solution and place in an oven at 103°C (floc).The initial humidity of the oven shouldbe increased by 300 ml of water in the oven 30 placing a shallow tray containing ^minut& before ad&g the test cubes. Dry for 16 hours.

9.

Remove cubes andd o w to cool to 2OoC (BOC).

10.

Repeat steps7 to 9 until 15 cycles have been completed.

11.

Weigh the cubes(Wf) and calculate the percentage weight11 osS: % weight loss = 100 WPW~)-

W O 12.

Calculate mean percentage loss.


85


Appendix 12: Acidimmersion test 1.

Prepare a 20%(w/w) sulphuricacidsolution.

2.

Prepare six 50 x 50 x 15 mrn test pieces from each sandstone.

3.

Immerse the samples in 200 ml of suphuric acid solution and leave for ten days.

4.

Remove the samples and examine for surface changes. If there is any sign of decay, the sample has failed the test.


86


Appendix 13: Laboratoryprocedurefor determination of clay liquid limits

the

Equipment & reagents Pestle andmortar 125 pm sieve 2 large palette knives 1 small palette knife Wash bottle 500 ml beakers Large watch glass Casagrande apparatus/Cone penetrometer Glass weighing bottles Analytical balance,0.01 g readability,1kg capacity Drying oven (110°C) Large square glass plate(400 by 400 mm approx.) Distilled/deionised water Preparation of clay pastes 1.

Gentlygrind100 g dry clay to pass 125 pm screen.

2.

Mix e125 prn dry clay thoroughly with a small amount of distilled water on the glass plate using the palette knives for at least 15 minutes to obtain a stiff paste. DO NOT add an excessive amountof distilled water as the resulting paste be must not be too fluid.

3.

Place clay paste in a beaker, cover with a watch glass to prevent evaporation and allow to 'age' overnight.

Determination of liquid limit: Conepenetrometer method 1. Remove the clay paste fiom the beaker and work the clay on the glass platewith the palette knives for about 10 minutes. 2.

Place a portion of the clay into the cup with a palette M e taking care not to trap any air.Strike-off excess clay with the straight edge of palette knife toobtain a smooth level surface.


87


3.

Position the cup in the centre of penetrometer base plate. Lower the penetration coneuntil the tipof the cone just touches the surface of the clay:if the cone is correctly positioned a slight movement of the cupwill just mark the surfaceof the clay. Gently lower thedial gauge stem untilit contacts the top of the INNER knob at the centre of the gauge. cone shaft by using the OUTER Set the dial gauge reading to zero by adjusting the knob at the centreof the gauge.

4.

Release the cone for a period5of seconds using either the (if using manual release, avoid automatic or manual release this action). After locking the cone jarring the instrument during in position, gently lower the dial gauge stem untilit contacts the top of cone shaft by using the INNER knob at the centre of the gauge. Record the gaugedial reading (penetration depth) to the nearest 0.1 mm.

5.

If penetration depth is less than 15 111111, add more water to the clay and repeat steps2-4. If the penetration depth is greater than 15 mm proceed to step6.

6.

Repeat steps2-4 until two subsequent dial readings arewithin +1 mm. This ensures consistent results.

7.

If the conditionsin step 6 are satisfied remove a small amount of clay paste(10 g approx.) from the area penetrated by the cone and placein a weighing bottle (massM1) and replace airtight lid. Weigh the bottle containing the wet clay (mass M2).Open thelid and place ovemightin an 105OC oven. Thebottle plus dxied clay is then weighed thefollowing morning (mass M3). Moisture content is then calculated as percentage of the dry mass of sample (see worksheet).

8.

Repeat steps1-7 at least three more times adding additional increments of distilled water.Mix very thoroughly each time more wateris added. Amounts of water added shouldbe such that penetration valuesin the range15 mm to 25 mm are obtained. Moisture content/penetration depth co-ordinates are plotted on the graph paper on the worksheet and are then connected by a straight line ‘best fit’ (the flow curve).

9.

The liquidlimit is reported as the moisture content, expressed to the nearest whole-number’ corresponding to a penetration depth of 20 mm on the flow curve.

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Determination of liquid limit:Casagrande method. 1.

Remove the clay paste from the beaker and work the clay on the glass platewith the palette knives for about 10 minutes,

2.

Place a portion of the remixed clay in the cup of the Casagrande the apparatus, apparatus and level-off parallel to the of base ensuring that there are no entrapped air bubbles. Carefully draw it normal the grooving tool supplied through the paste, keeping to the surface of the cup with the chamfered edge facing the direction of movement.

3.

Having first ensured that the counter is set to zero, steadily tun the crank at the rate of two revolutions per second until the paste 13 m at the bottom of the groove closes up over a length ofm. This distance maybe measured with a ruler or the end of the grooving tool. Record the number of bumps at which this occurs.

4.

If the number of bumps is greater than 50, add more water to the 3. If the numberis less than 50 clay and repeat steps 2 and proceed to step6.

5.

If the conditions in step4 are satisfied remove asmall amount of clay paste(10 g approx.) from the area of the groove and place in a weighing bottle (mass M1) and replace airtight lid. Weigh (mass M2).Open the lid and the bottle containing the wet clay place overnightin an 105°C oven. The bottle plus dried clay is then weighed the following morning (mass M3). Moisture content is then calculatedas percentage of the dry mass of sample (see worksheet).

6.

Repeatsteps 1-5 at least three more times adding additional increments ofdistilled water. Mix very thoroughly each time more water is added. Amounts of water added should be such that bump values are evenly scattered above and below 25. Bump values of less than 10 are discounted. Moisture content/bump value co-ordinates are plotted on the semilogarithmic graph paper on the worksheet and are then connected by a straight-line ‘bestfit’ (the flow curve).

7.

The liquid limit is reported as the moisture content, expressed to the nearest whole-number, corresponding to 25 bumps on the flow curve.


89


NOTES The results obtained by using the two methods do differ (see Section 5.2.2). Where the liquid limitis less than 100 differences are not consideredsignificant as they are within the normal variation typically obtained using the Casagrande method. 100 the cone penetrometer methodis known However, for liquid limit values above to give LOWER values in comparison to the Casagrande test.


90


LIQUID LIMIT: CONE PENETROMETER METHOD Sample ....._... ..._. .............

Operator

Remarks ..........................

Date ._.......... ....

...._....._..._..........

r

Determination No.

2

1

M1 ... Mass-emptybottle (9)

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W,. Mass bottle + wet day (9)

W... Mass bottle

+ dry clay (9)

3

I

I 1

5

4

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-

Mass water (9)=M2-M3 M a s s dry clay (9)=M3-M1

Moisture content (%) = (W-M3)/(M3-M1)’100

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Penetration depth (mm) k

28 26 E E,

24

W

222

:

.c

20

0 .-

jj 18 L

16 a 14 17 --

Moisture content, %

Liquid limitworksheet(Conepenetrometermethod)

Mineralogy and Petrology Group, British GeologicalSuwey 0 NERC 1994

91


LIQUID LIMIT: CASAGRANDE METHOD

Sample ........................... Remarks ..........................

Operator ......................... Date ................

AD

LO

50

Number of bumps

Liquidlimit worksheet (Casagrande method)


92


Appendix 14: Determination of plastic limit and plasticity index Equipment & reagents Pestle and mortar 125 pm sieve Wash bottle Glass weighing bottles Analytical balance,0.01 g readability, 1kg capacity Drying oven (1 10°C) Large square glass mixing plate (400 by 400 mm approx.) Polished glass test plate Metal or glass rod,3 mm diameter, approx. 100mm length Distilled/deionised water Method 1.

Gently grind approximately25 g dry clay to pass125 pm screen mix water with the and place onmixing plate. Using your hands sample until a plastic ball can be formd.

2.

Mould the ball between the fingers andit roll between the palm of the handsuntil the heatof the hands hasdried the clay sufficiently for slight cracks to appear on the surface.

3.

Divide the ballinto two sub-samples and set one of these aside.

4.

four equal parts and carry Divide the remaining sub-sample into out steps5-8 separately on each part

5.

Mould the clay using the fingers to equalize the moisture distribution. Form the clay intoa thread of about 6 mm diameter of each hand. between the first finger and thumb

6.

Roll the thread between the fingers of one (from hand the of the glass test fingertips to the second joint) and the surface plate. Use enough pressure to reduce the diameter of the thread from 6 mm to 3 mm in five to 10 complete forward-and-back hand movements. Use the rod to gauge the thickness of the thread. All clays tend to harden near the plastic limit;some “heavy” clays may require 10-15 movements. It is important to maintain uniform rolling pressure: do not change hand pressure as the thread diameter approaches 3 mm.


93


7.

On completing the operationin step 6, pick up the clay thread dry the clayfurther.Gradual drying and mould using fingers to is carried out by alternatelyrolling on the test plate and moulding with the fingers. Continual rolling should be notattempted as this only dries the surface of the clay. Reform the clay ball into a as describedin step 5.

8.

Repeat steps6 and 7 until the thread shears (cracks)both longitudinally and transversely when it has been rolled to about 3 mm diameter. Gather thecracked portions of clay and transfer to an airtight bottle(mass M1) and replace the lid immediately.

9.

Carry out steps5-8 on each of thefour portions of the clay, placing all the cracked piecesof clay obtained into the same airtight bottle.The bottle and its moist clay contentsis then weighed (massM 2 ) . After opening lidof bottle, place overnight in an 105OC oven. The bottleand dry clay is then weighed the following morning (mass M3). Results canbe recorded on the liquid limit worksheets and the moisture content then calculated.

10.

Cany out steps4-9 on the remaining material.

11.

two moisture contents obtained and Calculate the average of the This is the plasticlimit. express to the nearest whole number.

12.

The plastic index(PI) can be calculated by subtracting the plastic limit (PL)from the liquidlimit &I,).

NOTES (i) Test should be carriedouton a polished glass surface. If possible use separate plates formixing and testing as discrepancies will result fromuse of a textured or scratchedglass surfice. (ii) If moisture content of each sub-sample differs by more than +1% repeat the test.


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Appendix 15: Determination of green-to-dryandfired properties In BGS laboratories, fired propertiesof brick clays are determined using be used to small extruded test pieces. These test pieces can also determine green-to-dry properties (including shrinkage). Where large numbers of clay samples are being processed - e.g. in a regional survey of clay resources- extruded test pieces provide a means of providing a uniform test pieces relatively rapidly. Test pieces can also be m d e by hand moulding briquettes. A small hand-operated extruderwill provide approximately 10 test pieces50 mm long by6.3 rnm in diameter from about 100 g of dry clay. Test piece extrusion and determination of green-to-dry properties Apparatus

Pestle and mortar 125 pm sieve Hand-operated extruder fitted with 6.3 mm die Glass plate with distilled water Hand-operated plant sprayer filled Large pallet knife Steel rod (orsimilar) about 300mm long by 10 mm in diameter Mounted needle 4-figure analytical balance with capability to weigh a suspended object 50 ml beaker filled with kerosene Oven set at110°C Top-loading two-figurebalance Mercury displacement apparatus (rack and d e assembly) Beaker filled with sufficient mercury to allow test piece be to completely covered to known a depth Method 1.

Gentlygrind lOOg dry claytopass 125 pm screen.

2.

Spread the dry clay on a glass plate and spray with water whilst mixing the claywith the pallet knife.

Mineralogy and Petrology Group, British Geological Survey 0 N€RC 1994

95


3.

Continue adding water and mixing until the clay- begins to changecolour,developsa‘crumbly’texture,and/orsmears when squeezed between finger and thumb.

4.

Tip moistened clay into the barrel of the extrudertamp and down as much air as possible from the clay. using steel rod to remove

5.

Assemble plunger mechanism and rotate handleuntil 30 or 40 mm of extruded clay appears through die. Cut this materid off and discard.

6.

Whilst attempting tomaintain an even rotationof the extruder handle, cut about10 test pieces from the clay extrusionitas appears. Discardany bent or cracked pieces.

7.

Number each test piece usingmoaunted needle and carefully set down ona flat glass or ceramic tile or tray.

8.

Select one test piece immediately for weighing in air using four figure balance. Record weight of green test piece in air on greento-dry properties worksheet.

9.

Suspend green test piece from balance (use nylon monofilament in kerosene. Ensure that the test piece or similar) and submerge is not touching the sides of the beaker. Record weight of the green test piecein kerosene on worksheet.

10.

Oven dry all test pieces overnight 1at10°C.

11.

Weigh previously selected test piece in air and record.

12.

Record weight under mercury of empty rack and cradle assembly.

13.

Record weightof selected test piece under mercury.

14.

Calculate waterof plasticity, porosity of fired body and green-todry shrinkage using formulae provided on the green-to-dry properties worksheet.

Mineralogy and Petrology Group, British Geulogicai Survey 0 NERC 7994

96


Determination of fired properties Apparatus

Top-loading two-figure balance Mercury displacement apparatus (rack and cradle assembly) Beaker filled with sufficient mercury to allow test piece be to completely covered to a known depth Temperature-gradient kiln or programmable muffle furnace (ma. temp. 1250°C) Vacuum desiccator Vacuum pump Method 1

Weigh in air eight of the remaining oven-dry test pieces. Record these and other weighing data on the fired properties worksheet given below against individual test piece number.

2.

Record weight under mercury of empty rack and cradle assembly.

3.

Record weight of each oven dry test piece under mercury.

4.

Place each test piece in one of the eight cells in the temperaturegradient kiln. The maximum temperatureof each cell ranges from 900°C (cell 8) to 1250°C (cell 1). The heating rate is about 30 aminute 4OC/minute;this allows the firing cycle (including within isotherm or‘soak’ at maximumtemperature) to take place the working day. If a kiln of this typeis unavailable, then a suitable laboratory muffle furnace can be programmed to heat of temperatures. This is individual test pieces to the same range more time consuming although different samples can be batched together to befired simultaneously.

5.

Allow the kiln to cool overnight. Repeat steps 1to 3 with fied test pieces.

6.

Submerge test pieces in a dish filled with distilled water. Place the dishin the vacuum desiccator and evacuate for 3 hours.

7.

Remove individual test pieces from water, dry off any excess and immediately weigh.

a


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8.

Calculation of fiied properties is carried out as follows (see also worksheets 1 and 2 below): Before firing c = weight of test piece d = weight of test piece under mercury h = weight of empty assembly under mercury After firing e = weight of test piece f = weight of test piece under mercury hf = weight of empty assembly under mercury g = weight of test pieceafter water absorption ab (water absorption) = 100 x (g-e)/e vf = 100/~X (f-hf)/13.557 v = 100/~ X (d-h)/13.557

Porosity (vol. %) = 100 x ab/vf Shrinkage (vol. %) = 100 x (v-vf)/v Bulk density = 100/vf Specific gravity = loO/(vf-ab)

Note: Mercury weighings shouldbe carried out in a suitable fume cupboard.


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Sample No

......... a

a: weight greentest piece in air b weight greentest piece in kerosene

c: weight dry test piece in air d weight dry test piece in mercury h: weight empty assembly in mercury WATER OF PLASTICITY

...........g.

b.. .........g. c ...........g* d ...........go h ...........g. = la-c)

*

100

.........wt

%

C

volume green body (gv)

gv ...........

= la-b)

0.789 volume dry body (dv)

= Jd-h) 13.557

dv ...........

volume dry solids (ds)

= gv+c-a

ds ...........

pore volume of dry body (pv)

= dv - ds

pv ...........

POROSITY OF DRY BODY

=

*

100

.........VOl.

%

dv =pv

PV

PV ...........

* C

=ds

DS

* XU

DS ...........

C

DRY SHRINKAGE FROM WATER OF PLASTICITY

= W o f P - P V * 100 WofP+DS

Green-to-dry properties worksheet Mineralogy and Petrology Group, British Geological Survey0 NERC 1994

.........Vol.

%

99


Results of ceramic tests After firing'

Beforefiring C

Sample code & firing temp (dried

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Wt of

testpiece under under 110')

e d h Wtof Wtempty Testpiece assembly testpiece Wt mercury mercury after firing mercury

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Fired properties worksheet 1. Mineralogy and Petrology Group, British Geological Survey 0 NERC 1994

Calculation of firing properties

Sample:

1

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