Sustainable Utilization Of Quarry By-products 4b62q

<64 mm

Bedrock deposits

Deposits: superficial, bedrock

Composition: cobbles quartzites, igneous rocks, clay, silt Composition: similar to rock, but with Possibility of higher quantities of chert and clay; some included vein streams may also contain small amounts minerals of vein materials such as galena, sphalerite, pyrite, barite;

Particle size:

Limestone

Igneous and metamorphic rock

Sandstone

Composition: limestoneà calcite (CaCO3); dolomite/dolomitic limestoneà 10-50% dolomite (CaMg(CO3)2, calcite Particle size: various sizes following end product requirements, normally <10cm Extrusive bodies are of variable quality; -Intrusive bodies are of variable size; Particle size: depending on end use, normally < 10cm -rock types: granite, diorite, olivine dolerite and so on Wide range of sandstone types/ deposits; Particle size: depending on end use, normally < 10cm

Production residues characteristics Superficial deposits

variable quantities depending on the local topography and geology; non-hazardous Large variation in sizeà very large oversize Possibility of blocks and very fine undersize particles; radioactive inert / non-hazardous [low hazard] and asbestiform minerals in fine tailings inert material

Table 8: Characteristics of primary aggregates and associated (BGS, 2003)

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Potential host for uranium ore deposits

Sustainable Aggregates Sustainable Utilisation of Quarry By-Products

The lack of actual data for mineral waste is seen as an obstacle to utilisation. Taking as example recycled aggregates (that is, from construction, demolition and excavation waste), extensive surveys have been undertaken to determine exact arisings and availability. This is a very critical step towards their use, as knowing the volume, nature, geographical proximity and availability of materials can assist the identification of fit-for-use end markets and applications. A detailed feasibility study modelling the sustainable use of resources for the production of aggregates was undertaken for the West Midlands. This project investigated the supply of aggregates from primary, secondary and recycled sources including fines from crushed rock and sand and gravel quarries. This work developed an economic model that projects the potential sustainable resources for aggregate supply relative to construction demand, market price and resource availability (WRAP, 2006). The outcomes of this study are presented in more detail in Figure 5. Such feasibility studies are considered highly important for identifying benefits and obstacles to utilisation in a local/regional level and promoting the sustainable use of aggregates by balancing the use of recycled, secondary and primary materials. A similar study has been undertaken for Scotland (WRAP, 2007). Software tools and the principles of Mass Balance could assist to evaluate with greater accuracy the generation of quarry fines. Earlier research work has developed software to assist the planning and evaluation of aggregate resources according to fit-for purpose end uses. Such techniques could be employed even during early stages (that is, during exploration). The techniques use the principles of resource management and waste minimisation. Also software packages, such as the JK Simmet mineral processing simulator (JKTech, 2007), could assist to predict the generation of quarry fines. Mass balance has already found applications for various resources (for example, tyres, packaging, glass etc), but has not been extensively used for the mineral sector. A study undertaken on mineral resource availability and efficiency for the North-West region of England found out that (4sight, 2007): n There is a high demand for minerals in the North West. The North West is a major producer of minerals and aggregates, but also the biggest net importer of aggregates in the UK n Very little is known of the full environmental costs of mineral flows and information related to mineral resources flows are not of sufficient detail and consistency n Tracking minerals from exploitation through to end use and final disposal provides important information about a system’s efficiency, resource availability and management at the regional level. The use of any of the above tools would require the co-operation of the quarrying sector as the accuracy of results from studies using such research techniques would be dependent on provided data.

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Feasibility case study – Sustainable resourcing of aggregate supply Scope of project: Development of an economic model that projects the potential sustainable resourcing of aggregate supply relative to construction demand, market price and resource availability Case study location: West Midlands Resource and product groupings: primary (crushed rock, sand and gravel, dust (residual), scalpings (residual)); secondary (IBA, PFA, FBA, glass, used foundry sand); recycled (C&D waste, excavation waste) Key variables identified: supply, costs, market price, and demand Results – Shifts in resource use predicted for period 2004-2016 Crushed rock: n Recycled aggregates will be used increasingly for subbase and higher value graded aggregates (including concrete and asphalt) resulting to a significant market lose for crushed rock products. n The production of low grade fills and scalpings will have to be increased to meet market demand and this will require changes to the output profile of crushed rock quarries. This increase is due to the shift of recycled aggregates to higher value products. The production of scalpings may remain uncompetitive due to distance from market. n Changes in production sales profile of crushed rock quarries will lead to a reduction in average selling price and potentially increase the production of crushed rock fines above market demand. Sand and gravel: n Recycled aggregates use will shift to higher value graded aggregates therefore sand and gravel producers will lose market share (market share falls from 19% to 15%) Scalpings: n These are used as fills to replace the demand previously met by recycled aggregates Surplus fines: n Stocks continue to rise. The costs of processing the material to a fine aggregate for concrete (according to the model) are uneconomic. Sensitivity analysis: n Removal of the aggregate levy and equivalent reduction in the market place did not affect the market of crushed rock products. This is due to the cost effectiveness of recycling in West Midlands and the proximity of sources of recycled materials to sources of aggregate demand and the relative distance of primary resources. Other results: n Investment in washing plants for the processing of crushed rock fines and scalping may be needed. Also there is a need to develop processes that minimise the production of dust. Figure 5: Feasibility case study on the sustainable use of resources for the production of aggregates in West Midlands (WRAP, 2006)

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3.2 MINIMISING THE GENERATION OF QUARRY FINES The minimisation of quarry fines is perceived as essential in order to achieve resource efficiency, environmental protection and optimisation of the quarrying process. There is a need to minimise quarry fines for compliance with current legislation and the planning process. Environmental protection and social responsibility is of vital importance to the quarrying sector to reduce any adverse consequences (for example, in health and safety) and costs associated with the production of quarry fines (for example, storage, dealing with arisings transport, and handling). The minimisation of quarry fines could be achieved by carefully deg the quarrying process even during the early stages of exploration. Research projects carried out at Leicester University focused on minimising the inaccuracies associated with resource evaluation through statistical analysis and by exploring drilling techniques (Jeffrey et al, 2004) (project code: MA 3/2/002). A second project looked at developing a tool that could be used to identify the parts of a deposit that can produce good quality products with least waste, and thus to optimise extraction. This tool used the techniques of image analysis together with software development (Jeffrey et al, 2003a; Jeffrey et al, 2003b) (project code: MA 3/2/001; MA 4/02/002). The generation of quarry fines is due to extraction and processing operations in a quarry. As discussed in Section 2.2.1, there are several parameters that influence the production of fines, which are relevant to the rock characteristics and the involved processes. However, careful design and optimisation of extraction and processing could minimise fines production. A good practice guide mainly focusing on comminution is presented in the “goodquarry” website and in Table 9 (The University of Leeds, 2007c). Modelling tools can assist the quick performance evaluation of quarry operations. Research projects, part of the MIST programme, have undertaken work using process flowsheet simulators, such as the JKSimMet (JKtech, 2007) and Bruno (Metso minerals, 2007) and they have produced several case studies for sand and gravel (Figure 6) and crushed rock quarries ( University of Nottingham, 2003; University of Nottingham, 2005; Mitchell, 2007a; University of Leeds, 2007) (project code: MA 2/3/007; MA 4/1/002; MA 4/5/003) . The benefit in using such tools is that changes to equipment settings (crushers, screens), material flow rates or alternative circuit configurations (such as replacing a cone crusher with an impact crusher) can take place through the software, and the subsequent changes in the throughput tonnage figures and product grading can be explored. The constructed model (depending on software package) can be calibrated to take into the physical and breakage characteristics of the rock and it may also be possible to understand and monitor the performance of equipment. Modelling can be seen as an inexpensive way to achieve optimisation in processing operations and models can be produced using either theoretical or real data. The reliability of constructed models is closely related to the accuracy of data input. Therefore, process audits combined with mass balance studies are considered essential in collecting appropriate data. The use of software tools could assist to optimise plant processing routes with the scope to minimise the production of quarry fines, but in order to validate such studies, results should be accompanied by pilot or full scale trials. Case studies (such as the example given in Figure 6) demonstrate that it is possible to reduce the production of quarry fines, nevertheless costs associated with modifications to flowsheets may not necessarily balance the benefits seen from reduced quantities of fines. However, feasibility studies could provide the detailed information needed to decide whether a modified processing route is viable.

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Sandstone Quarry – Mid Wales – Three stage crushing circuit Feed 700mm medium Sandstone

Screen 105mm Feed 400 tph Undersize 174tph

Jaw Crusher Feed 226 tph Setting 125mm

Aggregate Product 0/20 250tph 100%

Horizontal Shaft Imapct Crusher Feed / output 250 tph Tip speed 45 m/s 35mm setting

Cone Crushers Setting 14mm Feed / output 79 tph

Feed 700mm medium Gritstone

Screens 40 / 20 mm Feed / output 329 tph Output 12 tph +40mm 67 tph +20mm 250 tph -20mm 0/20 Aggregate

Screen 105mm Feed 400 tph Undersize 174tph

Jaw Crusher Feed 226 tph Setting 125mm

Process Flowsheet Modified process circuit

Aggregate Product 0/20 300tph 100%

Cone Crusher Feed / output 300 tph 35mm setting

11

Cone Crushers Setting 14mm Feed / output 167 tph

Process Flowsheet Original process circuit

Screens 40 / 20 mm Feed / output 467 tph Output 45 tph +40mm 122 tph +20mm 300 tph -20mm 0/20 Aggregate

Conclusions: n Process change: replacement of a horizontal shaft impact (HIS) crusher with a cone crusher n Product: 0/20 aggregate has been increased from 250 to 300 tph from the same feed rateè 20% increase in production n Fines: the proportion of fines has been decreased from 38% to 30% è 21% decrease in fines production Figure 6: Case study example using the Bruno mineral processing simulator (Mitchell and Benn, 2007; The University of Leeds, 2007b; Metso minerals, 2007)

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Quarry fines are produced from various activities, but the stages of blasting and comminution are considered the most liable to generate such fines. The amount of dust produced during blasting is estimated to be as high as 20% (The University of Leeds, 2007c). Investigation into the quarry fines generated at various crushing stages was carried out and some of the results are presented together with good practice suggestions, in Table 9 (The University of Leeds, 2007c). Research undertaken by BGS identified that the quarrying sector would consider using new technologies which reduce fines production if they were economically viable and that further research work is required in identifying the capital and operational costs associated with quarry fines (Mitchell, 2007a) (project cost: MA 4/5/003). When trying to optimise comminution circuits, all parameters of influence should be taken into consideration including the physical properties and characteristics of the rock, the mechanisms involved in various processes and operational parameters (Petavratzi, 2006). Knowledge gained from comminution research (Evertsson, 2000; Bengtsson and Evertsson, 2006; Svedensten and Evertsson, 2005; Napier-Munn et al, 1996) should be used by quarry operators to optimise the performance of their equipment and to achieve lower quantities of quarry fines. The generation of quarry fines may cause adverse impacts on the environment (such as the local air, land, water, flora and fauna) and human health, and the mitigation of potential impacts is mandatory. Commonly, various dust control practices (conventional or alternative) are employed to minimise the impact of dust generated by quarry activities (Petavratzi et al, 2005; Petavratzi, 2006; EIPPCB, 2006). Health issues and the protection of fauna and flora are addressed through the management and protection of air quality. Fines produced from sand and gravel operations are commonly separated from the wanted fraction in washing plants and silt/clays are stored in lagoons. Although this process avoids the production of dust, it results in water consumption. Research has investigated the waterless removal of fines (Mitchell, 2007b) (project code: MA 4/5/002) as a different approach in reducing water consumption, and this is reviewed elsewhere (The University of Leeds, 2007a). Quarry fines are often stored in stockpiles prior to use within the quarry or in other end applications. A substantial quantity of quarry fines are replaced in the void created during aggregate production, once activities in a specific quarry have been terminated. In accordance with the Best Available Techniques document on the Management of tailings and waste rock, good management of waste rock can be achieved by minimising its volume in the first place and by maximising opportunities for the alternative use of production residues (EIPPCB, 2004). The generation and minimisation of quarry fines is investigated in more detail by sub-theme ‘Optimising the Efficiency of Aggregate Production’. The following Sections of this report focus on utilisation opportunities available for quarry fines.

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Production stage Primary crushing

Secondary crushing

Tertiary crushing

Rock type Igneous and metamorphic

Proportion of fines in the crusher product (weight %) 3 - 6% (j)1 to 10 - 15% (g)

Limestone

6 - 7% (j) to 20% (hm)

Sandstone

1 - 2% (j) to 15 - 20% (j, g)

Igneous and metamorphic

0 - 23% (c)

Limestone

15 - 25% (c) to 30% (hm)

Sandstone

10 - 15% (c)

Igneous and metamorphic

5 - 30% (c) to 40% (hm)

Limestone

< 20% to 40% (hm)

Sandstone

~15% (c) to 40% (hm)

4

Good practice Changes at the closed side setting (CSS) of jaw crushers (optimising the CSS) or the feed system (such as replace choke system with nonchoke system) may reduce fines. Overall, small quantities are produced (<5%) and any changes may have little effect on the total arisings of quarry fines. During secondary and tertiary crushing higher quantities of quarry fines are produced and minimisation of them will have an effect on overall fines production. Pre-screening of the feed can remove a substantial proportion of fines, avoid packing of material in the chamber and introduce a more uniform feed distribution to the crusher. Optimisation of the closed side settings of crushers may reduce fine material. The rotor speed of impact crushers is directly proportional to the production of fines. Slower rotor speeds may reduce the amount of fines produced.

(j) refers to jaw crushers (g) refers to gyratory crushers (c) refers to cone crushers (hm) refers to hammermill/impact crusher during crushing (The University of Leeds, 2007c) Table 9: Estimation of quarry fines produced

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4 UTILISATION OPPORTUNITIES FOR QUARRY FINES The utilisation of quarry fines is seen as a way to minimise the accumulation of unwanted material and at the same time to maximise resource use and efficiency. As discussed in Section 2.2, utilisation opportunities for quarry fines are identified by the end , when fit-for-purpose criteria become available that allows their use.Various utilisation prospects exist for quarry fines, which can broadly be classified into unbound and bound applications. Both categories of end uses may require some degree of processing of the quarry fines to be undertaken in order to comply with technical specifications. End uses falling within any of the above categories are presented in detail in the following Sections. End applications may be of high or low value, or may require a small or a large volume of quarry fines. Where applicable, the above issues are discussed. Figure 7 illustrates the applications reviewed in this report. Some quarry fines may already be used in some of the discussed uses shown in Figure 7 or they may be future utilisation opportunities. Again, these parameters are discussed where appropriate. Applications Unbound soil remineralisation, compost, artificial soils, remediation

Bound concrete hydraulically bound mixtures

site restoration, landscaping manufactured aggregates road pavements ceramic products embankment construction landfill capping

asphalt pavement, bituminous blocks

filler applications

synthetic rock

manufactured sand

kerbs

cement making

fibre reinforced pre-cast units

green roofs

grout products

straw and clay blocks

Figure 7: Current and potential unbound and bound applications for quarry fines

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4.1 THE USE OF QUARRY FINES IN UNBOUND APPLICATIONS Quarry fines may find use in several unbound applications as substitutes of primary aggregates, for example, in unbound aggregate mixtures, such as subbases and cappings. Technical specifications for aggregates are set by standards, for example BS EN 13242 for unbound mixtures (BSI, 2002b), with the ing National Guidance given in PD 6682-6 (BSI, 2003f). A summary of the content of the European standard and National Guidance document is given by the Quarry Products Association (QPA, 2004). Specifications for unbound mixtures products and the specifications describing unbound mixtures of aggregates are found in European Standard BS EN 13285. In the UK BS EN 13285, applies to granular sub bases and cappings. The aggregates in unbound mixtures must conform to the requirements of the BS EN 13242 for: n Crushed, broken and totally rounded particles n Resistance to fragmentation n Magnesium sulfate soundness A summary of BS EN 13285 is found elsewhere (QPA, 2004).

4.1.1 BULK FILLING APPLICATIONS Quarry fines are commonly used in reclamation of mineral workings, both alongside the development of quarrying activities and during closure. Reclamation can be an economically viable use for quarry fines, because the material is used on site instead of being transported to a different location/end (Manning, 2004) (project code MA 2/4/003). Reclamation plans are controlled by the permission granted to a quarry site. (DCLG, 2006b). Backfilling or infilling of voids is applied in surface and underground mineral workings, although there are cases where void filling is unnecessary (DCLG, 2006b). For instance, the extraction of sand and gravel deposits frequently means that the workings extend beneath the water table. In these cases partial filling and landscaping can convert such sites into recreational areas (Bell, 2007). Infilling voids may use various materials such as quarry fines, overburden material, tailings, slurries from lagoons, and inert waste. The physical and chemical properties, the bulking and settlement characteristics, and the compaction and stability of the fill are of great importance in backfilling or infilling activities (DCLG, 2006b). The use of quarry residues in quarry filling void applications is classified as high volume and low value. Often a flowable fill is required for irregular, non-uniform voids and a case study demonstrating the use of quarry fines in infill grouts is given in Section 4.2 (bound applications). Sometimes quarry fines are used for landscaping purposes within the quarry, while this is still in operation. Quarry fines may also find use in general fill applications such as embankments, which are considered as low value, but again they may require large quantities of materials. Currently several other alternative and secondary materials are utilised in similar ways; therefore, quarry fines will have to compete in the same markets as these materials, and with primary aggregates. Whether quarry fines are used in general fill applications will be determined primarily by the cost of transport. Where demand for such uses exists in close proximity to quarries, then quarry fines could easily satisfy this demand.

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Research work investigated the use of sandstone quarry sand in engineering fill applications and confirmed its suitability. The research also identified that moisture susceptibility and frost heave would prevent its use in unbound subbase applications, unless processing removed or diluted the filler fraction (Lamb, 2005). The performance of recycled materials including building debris, crushed concrete, and quarry fines as replacement for traditional materials (that is, primary aggregates), used as fine aggregate, was investigated by researchers (Touahamia et al, 2002). The shear strength characteristics of recycled materials and quarry fines were examined with, and without, reinforcement. Results suggested that recycled materials have lower shear strength values, but the presence of geosynthetic reinforcement in recycled materials and quarry fines increased the shearing resistance of materials (Touahamia et al, 2002). Overall, unprocessed quarry fines (Type 1 group materials as classified in Table 1) can be used as bulk fill in trenches, for backfilling underground caverns, in embankments, in landfill construction (that is, landfill capping), in offshore “reef bag” construction and other general filling applications (Ghataora et al, 2004). Several other examples from research papers are found in an earlier report on the Exploitation and Use of Quarry Fines (Manning, 2004) (project code MA 2/4/003). The geotechnical criteria that specify material suitable for use as fill are described in the European Standard BS EN 1997-1 (BSI, 2004a) and a summary is shown in Table 10. Principle requirements to be considered n good material handling properties

Applications fills beneath foundation and ground slabs

n adequate engineering properties n transport/storage requirements

backfill to excavations and retaining structures general landfill including hydraulic fill, landscape mounds and spoil heaps

embankments for small dams and infrastructure Fill properties Grading; resistance to crushing; compactibility; permeability; plasticity; organic content; chemical aggression; pollution effects; solubility; susceptibility to volume changes (swelling clays and collapsible materials); low temperature and frost susceptibility; resistance to weathering; effect of excavation, transportation and placement; possibility of cementation occurring after placement (for example,. blast furnace slags). Table 10: Geotechnical requirements for materials used in fill applications (BSI, 2004a) Criteria Strength; stiffness; durability; permeability

4.1.2 ROAD PAVEMENT CONSTRUCTION The Specification for Highway Works allows the use of a range of reclaimed materials including quarry fines on a site (where construction occurs) specific basis (Highways Agency, 2007a). Series 600 on Earthworks set the specifications for bulk fill materials which find application either as a general granular fill or/and general cohesive fill (Highways Agency, 2007a). These specifications set detailed criteria for unacceptable materials, which are determined by their potential hazardous nature and adverse physical properties (such as, grading, moisture content, plasticity etc). Also Series 600 puts the requirements for materials used as capping on their own or as part of a mixture. Table 11 provides a summary of material properties requirements as set in Series 600. Series 800 sets the specifications for unbound mixtures for subbases, which have to conform to BS EN 13285 (BSI, 2003a) and the properties of aggregates must comply with BS EN 13242 (BSI, 2002b). For Type 1 Unbound mixtures only up to 10% by mass of fines below 4 mm is permitted.

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Previous research has investigated the use of quarry fines in road construction (Hills et al, 2001; Touahamia et al, 2002; Lamb, 2005; Rockliff, 1996; Rezende et al, 2002). Research undertaken by TRL explored the suitability of unbound sandstone quarry sand (SQS) in a 20 metres cycle path as well as the use of SQS underlain with scalpings. The unbound section performed well and showed no signs of deteriorations during the research. The section that combined the scalpings with the SQS performed well initially, but after a period a noticeable channel appeared that highlighted the potential for a large volume of water to washout any unbound material (Lamb, 2005). Other research investigated the use of alternative materials including quarry production residues in road construction and bulk fill (Hill et al, 2001). This work stated that it is more appropriate to simulate in situ loading (physical and environmental). Results suggested that the mechanical properties of alternative materials using performance based specifications are equally good to conventional materials and they could potentially be used as bulk fill (Hill et al, 2001). Another project investigated the use of quarry waste for the construction of low-volume roads. The test material consisted of 65.9% (by mass) of gravel, 12% (by mass) of sand and 22.1% (by mass) of silt and clay. The material was considered suitable to replace natural primary aggregates without incurring significant structural weakness. However, field studies suggested that the performance of this material is dependent of its moisture content, which is affected significantly during rainy periods (Rezende, 2003). Material description

Critical material properties

Granular material as general fill

• • • •

Cohesive material as general fill

• • • • •

BS 1377-part 2 grading BS 1377-part 2 plastic limit BS 1377-part 2 moisture content moisture condition value undrained shear strength of remoulded material BS 1377-part 2

Granular material as capping (fine grained )

• • • •

grading optimum moisture content moisture content Los Angeles coefficient

grading uniformity coefficient moisture content moisture condition value

In accordance with (BSI, 1990) BS 1377-part 2

BS 1377-part 2 BS 1377-part 4

BS 1377-part 2 Granular material as capping (fine grained) Complying with BS EN 13285 and BS EN 13242 – Unbound mixtures Table 11: A summary of Series 600 – Technical specifications for bulk fill materials in MCHW 1 (Highways Agency, 2007a)

4.1.3 SOIL ENHANCEMENT Quarry fines are considered a valuable additive to soils which may help to improve its quality by providing essential nutrients to plants (for example, iron, potassium, magnesium). Quarry production residues will tend to vary according to the source they are derived from. A summary of the benefits that may be seen from the use of quarry fines in soils is presented in Table 12 (Szmidt and Ferguson, 2004).

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Benefits Enhanced soil fertility and diverse soil biology Multi-season effects Enhanced plant establishment, growth and vigour Enhancement of flavour, aroma and shelf-life of produce High dry matter content, drought resistance, nutritional value and some plant disease resistance of plants In compost, increases in process performance with integrated resource use and Carbon sequestration by calcium and magnesium carbonate formation, microfloral accumulation and C-accumulation as soil and crop biomass Table 12: Benefits seen from the use of quarry fines in soil (Szmidt and Ferguson, 2004)

The use of quarry fines for remediation and soil improvement has been addressed by previous research (Madeley, 1999; Szmidt and Ferguson, 2004; Remineralize the Earth – online magazine, 2007). Quarry fines and dust may be used to enhance plant growth. Several projects have been undertaken (UK and overseas), which explored the use of a variety of crops with quarry fines containing soils such as brassicas with basalt/ glacial silt (Szmidt, 1998; Szmidt, 2004), soybean with sand and gravel fines (Angeles et al, 1997), acacia with granite fines (Oldfield, 1998) and other (Szmidt and Ferguson, 2004). Results varied for different trials and under some circumstances they were positive, whereas in other cases no significant changes were recorded (Szmidt and Ferguson, 2004; Remineralize the Earth-online magazine, 2007). Overall however the use of a suitable combination of crops with quarry fines can enhance plant growth. There is evidence that the use of quarry fines in soils may enhance crop value as well as animal and human nutrition. Plants grown in quarry dust – amended soils have higher levels of essential elements and nutritional values when compared to those produced by conventional agriculture. Recent research has identified that the nutrition content of fruits and vegetables has been dropping since initial records were taken (Szmidt and Ferguson, 2004; Remineralize the Earth-online magazine, 2007). Hence, finding ways to achieve soil remineralisation and nutrition content increase is considered critical. Another benefit seen from incorporating quarry fines in soils is that this action may have a positive effect on carbon cycling, but further research is required however to demonstrate this (Szmidt and Ferguson, 2004; Remineralize the Earth-online magazine, 2007).

4.1.4 COMPOSTING Quarry fines may also find application in composting. Research in this area has been less active and only a few trials have been undertaken. Results from some trials have not shown any clear benefits from the incorporation of quarry fines in compost. In another occasion, work at Glasgow University (Graham, 2001) and the Scottish Agricultural College (SAC) (Szmidt, 2004) has determined small but significant increases in compost temperature at relatively high rates of quarry fines (20 kg/m3). Also ammonia production from compost was lower in the presence of quarry fines suggesting a lower odour potential (Szmidt and Ferguson, 2004).

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In the UK, some extensive work, funded through the MIST project investigated the use of basaltic quarry fines with organic process residues for the development of growing media.Various combinations of quarry fines and compost were trialled and grass and tomato plant pot experiments were set up to assess the performance of different blends. Field trials, at a local quarry were also set up. The main parameters investigated were plants’ growth, the leachability of nutrients and potential contaminants, and physical properties (such as, infiltration, water holding capacity, and shear strength) of blends tested in lysimeters. Results suggested that most quarry fines interact positively with compost and vice-versa to allow development of novel growing media suitable for horticultural and land restoration uses. However, further research work is required to understand and assess the influence of quarry production residues on compost (Guillou and Davies, 2004) (project code MA 1/3/003). Specifications for composted materials are set by the Publicly Available Specifications for Composted Materials (PAS 100, 2005). The BSI PAS 100 covers various key elements related to composting such as process control, input materials, sanitation, stabilisation, quality requirements, sampling frequency, classification and others (PAS 100, 2005). However, according to PAS 100 and the compost quality protocol, quarry production residues are not included in the list of permitted materials (PAS 100, 2005; Environment Agency et al, 2007). The latter is limited to biodegradable materials only. The deliberate addition of nonbiodegradable materials (for example, basaltic fines) is not allowed. The provision of data that justify the suitability of quarry fines in the composting process could permit incorporation. This however will have to be classified on a case by case basis (Szmidt and Ferguson, 2004).

4.1.5 ARTIFICIAL SOILS Quarry fines may also be used to produce artificial soils. The British Standard BS 3882 (BSI, 1994) specifies topsoil requirements. According to BS 3882, three grades of topsoil are established, , the general purpose, and economy grade (BSI, 1994). Topsoil is classified to any of the above grades after review of the following characteristics (BSI, 1994): n n n n n n

Textural classification Maximum stone content pH value Nutrients content Loss on ignition Exchangeable sodium percentage

Past research into artificial soils suggests that blending quarry production residues (such as sandstone quarry sand) with organic material (i.e compost, agricultural waste) might produce an artificial soil (Lamb, 2005; Keeling et al, 2001; Mitchell et al, 2004). Results determined that the textural classification of grade topsoil can be achieved by using a 70:30 (v/v) blend of the filler fraction (<75 µm) of sandstone quarry sand or as produced sandstone quarry sand and a suitable organic material. The grading requirements for topsoil are met by the filler fraction, but not from the as produced sandstone quarry sand (Lamb, 2005). Specific types of quarry fines, such as from limestone quarrying activities may be used to remediate acidic soils. In a project funded through the MIST programme, limestone quarry fines were used in combination with steel slag fines and compost to remediate acidic colliery spoil sites. Grass growing trials were undertaken at various compositions of colliery spoil, limestone dust and steel slag. Results confirmed that the most appropriate mix will contain 5% of each limestone and compost and 4% of steel slag (Tarmac Ltd

36


and Associates, 2007) (project code: MA 4/2/019). Further research is currently undertaken from Birmingham University in remediated acidic sites using quarry wastes (project code MA 6/4/02) (Birmingham University, 2007).

4.1.6 FILLER APPLICATIONS Quarry fines may substitute primary materials which are used as fillers in paper, paint, plastics, rubber and elsewhere. Mineral fillers are used in a wide range of commodities and commonly comprise fine grained materials (<2 mm). Fillers used in certain end uses must fulfil specific requirements. For instance the production of photocopier paper and household paints must use fillers with high brightness levels and good rheological properties. In order to satisfy such demand, primary materials like kaolin, calcium carbonate or talc are used and sold at a relatively high cost in order to recover total production costs (extraction and processing). Quarry fines could not comply with the requirements for high value filler applications. Nevertheless they could be used as general fillers in papermaking (for example, packaging paper), pigments (for example, marine paint), plastics (for example, glass reinforced plastics), membranes and rubber (tyres, cable) (MIRO, 2001a; Bonney et al, 2000). Research investigated the use of mineral residues of calcareous and siliceous composition from aggregate quarries in end uses such as elastomeric membranes, paints, paper and plastic. The aim of this research was to develop low cost by-product fillers where product specifications and end use do not demand highgrade fillers. Siliceous and calcareous quarry fines have been shown to be suitable for use in elastomeric membranes and a large scale trial was carried out for the calcareous materials. Trials were undertaken to establish the compatibility of these materials with paints, but results were not positive. However it was found out that micronised calcareous quarry fines could partially substitute extenders and produce a reasonable quality of paints. The use of calcareous micronised quarry fines in the production of glass reinforced plastics was also examined and it was found out that partial substitution of extenders does not impair the quality of the s produced. Finally, micronised calcareous quarry fines could substitute up to 5% wood pulp in paper pulp without influencing the production procedure (MIRO, 2001a; MIRO, 2001b; Bonney et al, 2000).

4.1.7 OTHER APPLICATIONS Quarry fines could also find use in the production of Portland cement. The cement sector has been active in trying to utilise such material for the preparation of kiln meal (Petavratzi and Barton, 2007). The cement making process requires four major constituent oxides to be present, namely CaO, SiO2, Al2O3 and Fe2O3. Therefore, quarry fines with the above constituents may be applicable for use. Materials used in clinker’s recipe are blended to specification prior to use and it is anticipated that various other alternative materials may be found suitable. The production of meals suitable for cement is often undertaken by a secondary industry sector specialised in blending. Quarry production residues, which present some of the essential ingredients and low compositional variability, could be used in cement manufacture (Petavratzi and Barton, 2007). Current cement standards (BS EN 197-1) only refer to well established alternative materials (i.e pulverized fuel ash) commonly used for the production of blended cements (BSI, 2000a). The use of quarry fines and other alternative materials pre-kiln is relatively new and further research work should be undertaken to determine its full potential.

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Finally quarry fines might find application in new, innovative products such as green roofs, eco-friendly slates, cob building, light earth or straw clay, earth bags and earth plasters. In green roofs, clay, silt and quarry fines could be used in the soil and aggregate mixtures, and scalpings in the aggregate mixture. The particle size distribution and particle shape of quarry production residues are considered critical parameters that will determine their utilisation potential. Currently there are no specifications on green roofs in the UK and the market is limited, although it is anticipated that changes will be seen in the near future due to active research and development. Further information can be found in GreenSpec website (GreenSpec, 2007a) and the Green Roof Centre (The Green Roof Centre, 2007). Eco-friendy slates for roofing are produced by one manufacturer in the UK by resin-bonded recycled plastic and dolomite/limestone fines. Dolomite or limestone comprises a filler material in this application. Byproduct fillers derived from quarry fines might be suitable to this product, but further research should be undertaken to determine this. (E-C-B-UK, 2007; GreenSpec, 2007b). Quarry production residues could also be used in earth construction applications. For example, clay, silt and quarry fines could be used in cob building and straw clay end uses. Again more research work is required to determine the applicability of quarry fines in earth construction. More information on earth construction can be found elsewhere (Sustainable Build, 2007).

4.2 THE USE OF QUARRY FINES IN BOUND APPLICATIONS Quarry fines could be diverted and utilised in various bound applications such as controlled low strength materials, masonry products, asphalt and asphalt surface treatments, hydraulic bound mixtures and mortar. Technical standards (British and European) specify the requirements for aggregate materials used in bound applications. The BS EN 12620 sets the criteria for aggregates to be used in concrete (BSI, 2002a). The accompanying National Guidance Document PD6682-1 provides information on the application of the standard to the UK (BSI, 2003g). The product standard BS EN 13043 (BSI, 2002e) and the PD 6682-2 (BSI, 2003e) corresponds to aggregates used for asphalt and surface treatment. The BS EN 13242 (BSI, 2002b) and the ing PD 6682-6 sets the specifications for aggregates used in hydraulic bound uses (BSI, 2003f). Finally the BS EN 13139 (BSI, 2002c) and the National Guidance PD 6682-3 (BSI, 2003h) set the requirements for aggregates used in mortar. The content and relevance of the above technical standards with quarry production residues is discussed in the following sections together with findings from relevant research that demonstrate the potential utilisation of quarry fines in bound applications.

4.2.1 CONTROLLED LOW STRENGTH MATERIALS Controlled low strength materials (CLSM) are defined as self-compacting, low strength, cementitious materials used primarily as backfill in lieu of compacted fill (ACI, 1999).Controlled low strength material is characterised by high workability, low density and low strength, which allows for self-compaction. Fly ash, ground granulated blast furnace slag (GGBS), and waste foundry sand, are commonly found in flowable fill mixtures (Naik et al., 2003), but non-standard materials such as quarry fines may also be used to produce CLSM as far as they satisfy the requirements for intended applications. According to the Federal Highway istration’s (FHWA’s) Office of Research, Development, and Technology, quarry residues such as screenings, pond fines and baghouse fines can be used as a filler

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aggregate or as a partial or possibly a complete replacement for the pozzolan component in flowable fill mixes (TFHRC, 2007). Screenings may substitute sand, whereas pond and baghouse fines could partially or completely used instead of conventional aggregates. It is anticipated that fines produced from comminution and screening will not require any additional processing except from some minimal sizing or drying if they exhibit high moisture content. Pond fines will require some type of dewatering prior to use. Engineering properties of quarry residues that are of particular importance to quarry fines are gradation, moisture content and unit weight, whereas properties such as the mix strength, the flowability, the time of set and the bleeding and shrinkage determine the performance of the controlled low strength material (CLSM) (TFHRC, 2007). Research investigated the use of fly ash, rice husk ash and quarry dust as potential by-products in controlled low strength materials. Quarry fines were obtained from a granite quarry and comprised material below 4.75 mm. Trials explored different mixtures such as cement-fly ash-quarry fines, cement-quarry fines and cementrice husk-quarry fines (Nataraja and Nalanda, 2007). Engineering properties such as flowability, density, uniaxial compressive strength, stress-strain behaviour, water absorption and volume change were investigated. Results suggested that the engineering properties of CLSM can be achieved satisfactorily using a very small amount of cement and a large amount of quarry fines. When the by-product content was increased, the water-cement ratio also increased linearly to get a specific flow. Quarry fines could substitute sand in CLSM. Quarry dust content (<75 µm) as high as 96% by weight, could be mixed with flowable fill without noticeable segregation and bleeding. The uniaxial compressive strength test results were acceptable and the stress- strain behaviour results suggested that quarry fines could be used for soil-like material applications in producing CLSM (Nataraja and Nalanda, 2007). In another project quarry fines were used as the main constituent of a pumpable infill grout (Tarmac Ltd and Associates, 2007; Ghataora et al, 2004) (project code: MA 4/2/019). Laboratory trials and modelling studies were carried out to establish the constituents of potential mixes, and were followed by field trials that verified the pumping qualities of a selection of mixes (Ghataora et al, 2004). Limestone quarry fines below 4 mm were used in field trials and several mixtures were prepared with different ratios of water-cementquarry fines and in one of the trials foaming agent, whereas the effect of pumping aid was also investigated. Two different field trials were undertaken and both explored the ‘pumpability’ of different mixtures and the compaction properties. The objective of these trials was to examine the suitability of flowable fills in underground void filling and back-filling applications. The product expected to be utilised in underground void filling was required to have free flowing properties, to be able to be pumped long distances, to have a low strength and to contain a high content of quarry fines. The properties investigated for the material used as a backfill were the pumpability, 3-day strength, bleed and segregation after placement. Results suggested the following: (Tarmac Ltd and Associates, 2007) (project code: MA 4/2/019): n Quarry fines could be pumped by hydro-transport techniques using water only n Quarry fines could be developed into cementitious pastes and pumped over long distances n Pastes based on quarry fines can be pumped over long distances without segregating thus providing an alternative material to pulverized-fuel ash n Overall the pumpable grouts would be suitable for low value, bulk infill products such as void infill or reinstatement of utility excavations. Limestone quarry fines were used in one project as a substitute for natural sand (approximately to 50% by

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mass) for the production of self–compacting concrete (SCC). Fines content (<75 µm) of 10% (by mass) was included in the limestone quarry fines, which was absent in the natural sand. The substitution reduced the requirement for chemical ixtures, without affecting the strength of the self-compacting concrete (Naik et al, 2005). In one research, three types of limestone quarry fines were tested as substitutes for cement. Results suggested that a 10% replacement of cement with quarry fines produce a self-compacting concrete with good rheological properties in its fresh state and compressive strengths and drying shrinkage at hardened state (Felekoglu, 2006). The use of granite quarry fines in self-compacting concrete was investigated against limestone fines. Granite fines had a finer particle size distribution and higher flakiness index than its limestone equivalent. Research demonstrated that granite fines could be successfully incorporated into SCC. When granite fines were compared with limestone particles, then it was concluded that they required a higher dosage of superplasticiser for similar yield stresses and rheological properties for routine use in SCC. The consistency of quarry fines overtime may be an issue, and durability issues such as alkali-silica reaction should be investigated in detail (Ho et al, 2002). Other examples are reviewed by other authors (Manning, 2004) (project code MA 2/4/003). Geotechnical design and properties are determined by European standards (Eurocode 7) (BSI, 2004a), whereas the properties of the aggregates used in controlled low strength materials should comply with BS EN 12620 (BSI, 2002a).

4.2.2 CONSTRUCTION PRODUCTS – MANUFACTURED CONCRETE The use of quarry fines in concrete is well established, in particular where arisings become available from local sources (Manning, 2004) (project code MA 2/4/003). Technical specifications for concrete are given in BS EN 206-1 (BSI, 2000f)( and the complementary British Standard, BS 8500 (BSI, 2006a; BSI, 2006b) (part 1 and part 2). Other standards which relate to specific end products exist and some of them are summarised in Table 21 in Appendix IV (Price, 2002; WRAP, 2007c). Specifications for aggregates used are given in BS EN 12620 (BSI, 2002a). The production of concrete requires the use of coarse aggregate (>4 mm) and fine aggregate (<4 mm) and in some cases also filler aggregate (< 63 µm). Filler aggregates are obtained by processing natural, recycled or manufactured aggregates. In some European countries it is common practice to set a minimum fines content and to use fine filler aggregate, as it may be beneficial in minimizing voids and bleeding in concrete (BSI, 2003g) The “aggregates for concrete” standard specifies the geometrical, physical and chemical requirements for aggregates and a summary of them is given in Table 13. BS EN standard requirement Properties Geometrical Aggregate sizes Grading Aggregate shape Shell content Fines content Physical

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Fines quality Resistance to fragmentation Resistance to wear Polished stone value Aggregate abrasion value Durability

Applicable to/Methodology (Sieve apertures) Coarse and fine aggregate Coarse aggregate (flakiness index) Coarse aggregate Coarse, fine, filler aggregate (up to 11% for all-in aggregate) Fine/Filler aggregate (Harmfulness that is, clay content) Los Angeles method Coarse aggregates Coarse aggregate (for highways surfaces uses) Magnesium sulfate soundness test

Chlorides Sulphur rich compounds Other constituents Carbonate content


Chemical

Water soluble ion chloride Acid soluble sulfates and total sulfur Constituents that alter setting and hardening of concrete Fine aggregates – concrete pavement surface sources

Table 13: Requirements for aggregates for concrete according to BS EN 12620 (BSI, 2002a)

Technical specifications on the use of aggregates for mortar are set by BS EN 13139 (BSI, 2002c), with the ing National Guidance given in PD 6682-3 (BSI, 2003b). Grading requirements place greater emphasis on ‘consistency of products’ based on ‘typical grading’ figures with controlling tolerances and overall requirements on designated sieves (QPA, 2007). Quarry fines may be produced to comply with standards for concrete or mortar, specification. There are cases when the fines cannot meet the technical requirements, or the local concrete or/and mortar market cannot absorb the quantities produced, or that even a suitable local market may be absent. Under such circumstances, quarry fines remain unused. Unfortunately there is little data on the technical suitability and market availability for quarry fines to be used in concrete or mortar, and the only existing information comprises anecdotal evidence provided from interviews with the industry (Mitchell, 2007a) (project code: MA 4/5/003). According to such anecdotal evidence, hard rock and sandstone quarries produce fines as a result of high demand for 10 mm aggregate. At some hard rock quarries, demand exceeds supply and aggregate producers re-crush single-size aggregate to create more fines. Sandstone quarry fines produced from some sites are consumed locally, whereas some other sites have no sales and stockpiles are increasing, often matching a critical level, which constrains the continuity of quarrying activities (The University of Leeds, 2007a). Research has investigated the use of quarry fines in various concrete applications. The International Center for Aggregates Research (ICAR) explored the use of microfines (particles below 75 µm) in concrete. According to American Standards (ASTM C33) a maximum of 7% (by mass) microfines is allowed in some applications, when adverse constituents such as clay or shale are absent. Trials were undertaken using 63 samples of fine aggregate from seven different rock types and characterisation included standard tests such as specific gravity, gradation, absorption, uncompacted void content, as well as less commonly used tests, like laser diffraction, particle sizing, chemical analysis and the methylene blue method. Tests were conducted on mortar mixes containing fine aggregate. Findings suggested that manufactured fine aggregate mortars with high fines content generally had higher flexural strength, improved abrasion resistance, higher unit weight and lower permeability due to filling of pores with microfines. Compression strength and shrinkage were within generally acceptable ranges. Manufactured fine aggregate can be produced from a variety of rock types such as limestone, granite, quartzite, diabase and dolomite. Hence concrete can be manufactured using all of the aggregate, including microfines from 7 to 18% without the use of ixtures (Ahn and Fowler, 2001). The use of limestone fines (90% of material ing 300 µm), cumulated from limestone quarrying activities, was examined by one research project. This work looked at the use of limestone fines combined with Portland cement (with or without the use of waste glass powder) (Turgut, 2006). Other research looked at the use of limestone fines with a small quantity of Portland cement was explored for the production of artificial stone. Cement to limestone dust ratio and compaction pressure, were considered as the two independent process variables and compressive strength represented the dependent variable (Galetakis and Raka, 2004a; Galetakis and Raka, 2004b). Experimental work from both projects showed that quarry dust cement combination can be utilised for the production of moulded masonry blocks with acceptable

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mechanical and physical properties (Turgut, 2006; Galetakis and Raka, 2004a; Galetakis and Raka, 2004b). Hanson Aggregates manufactures structural concrete in Wales (Craig-yr-Hesg) using 12% unseparated sandstone quarry fines. The product is being sold as standard C35 strength concrete (35 N/mm2). However measurements identified that the strength of the final product would be considerably higher than 35 N/mm2 after 28 days. Therefore, it was proposed that, if the filler was to be removed, then much greater proportions of the coarser grained material could be incorporated into the mix, while retaining the desirable strength value (Lamb, 2005). Also sandstone quarry sand (SQS)is used in block manufacture, in a mass percentage up to 10% of 6 mm aggregate to prevent balling and voids. This is common practice for a number of companies in South Wales (Lamb, 2005). The filler fraction of the sandstone quarry sand (SQS) was tested as a cement replacement material. Physical and chemical analysis results determined that this material could be used as a cement substitute, subject to the end requirements and material’s availability. The leachate results showed a significant increase in lime, when SQS was added to mortar, which may cause efflorescence on concrete products. The pozzolanicity results were positive, but it was found out that this material contains a very high insoluble residue, which limits its use in cement only as filler. Although overall results were considered positive, it was thought that further work would be required to determine if additional routine testing requirements were essential for using SQS in cement. It was also unclear if it would be practical for the quarry to separate the filler from the SQS and also dry the material prior to inclusion with the cement mix (Lamb, 2005). The use of silt and clays (SiO2 composition) obtained from crushed granite stone (<150 µm and between 75 and 150 µm) was tested as cement substitutes and it was found out that up to 25% of cement replacement could be achieved without affecting the durability of concrete, namely parameters such as strength, workability and impermeability. Silt and clays expressed reactive properties and they could be used as reactive minerals. Although the inclusion of silt and clay increased the water / cement ratio, it was thought that the problem could be solved by using high specific surface area material with a superplasticizer ixture (Chan and Wu, 2000). The production of concrete for sea defence structures using limestone quarry fines was investigated by laboratory experimentation undertaken by the University of Birmingham. The aim was to produce concrete structures for erosion control. The strength of concrete at 28 days was higher than the specified, but the project did not move forward as economic evaluation showed that this application was not cost effective (Ghataora et al, 2004). An analytical literature review is presented in the report “Exploitation and use of quarry fines” and further literature findings can be reviewed there (Manning, 2004) (project code MA 2/4/003).

4.2.3 CONSTRUCTION PRODUCTS – HEAVY CERAMICS Heavy ceramics such as bricks, tiles and pipes could absorb some quantities of quarry fines from local sources, but it is expected that utilisation rates will be much lower than in concrete and controlled low strength applications. The market for bricks has changed significantly after the introduction of concrete blocks, as the latter replaced common bricks. This resulted to a shift to producing facing bricks used for aesthetic purposes (BGS, 2007). Brickworks commonly own clay quarries, which provide the primary raw

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materials. However, other constituents derived from primary, secondary and waste sources are also utilised in order to satisfy market competition, which requires from companies to produce large portfolios with different product. Technical specifications on masonry products, as described in BS EN 771-1, (BSI, 2003i) apply to ceramic products such as bricks and they set the requirements for a variety of physical properties such as density, dimensions, thermal properties, compression strength, water absorption and others. ’Fit-for-use‘ criteria for raw materials are not currently available, because historically brick manufacturers utilised only primary materials from their own clay quarries and the use of alternative materials has not progressed sufficiently to require the development of a new set of specifications. A recent research project looked at the utilisation of various alternative materials in brick making. A characterisation framework was developed based on end requirements. The framework aimed to characterise constituent materials according to their contribution to the end product (Petavratzi and Barton, 2006). The approach and findings of this research is presented in Section 2.2.2 and Table 4. Depending on the physical (that is, composition) and chemical characteristics (for example, soluble salts content) of quarry fines, they may be used as filler, clay substitute, colourant, fluxing agent or even body fuels (Petavratzi and Barton, 2006). Examples of quarry fines that could potentially be suitable for use in bricks categories are given in Table 20, in Appendix III. According to responses from brick manufacturers, the inclusion of quarry fines in bricks, in a percentage of 3 to 5% by mass, is possible without affecting the appearance and properties of end product. Nevertheless the brick sector will only choose to introduce materials to the process that will provide some clear benefits to the appearance of the end product (for example, desirable colour) or the manufacturing process (for example, fluxing) (Petavratzi and Barton, 2006). The incorporation of quarry fines in ceramic products has been explored by several other research projects and a summary of findings is shown in Table 14. A review of other literature sources can be found elsewhere (Manning, 2004) (project code MA 2/4/003).

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Project Acid resisting bricks from kaolin fine quarry residues, granulated blastfurnace slag (GBFS) and granite-basalt fine quarry residues

Findings The performance and characteristics of these bricks were compared with conventional ones made of clay, feldspar and sand. The study suggested that it is possible to produce acid resistant bricks, which satisfied the technical specifications in place, by using (by mass) 50% kaolin fines, 20% granite-basalt fines and 30% granulated blastfurnace slag at a firing temperature of 1125 oC. Recovered slate waste in This study examined the characteristics of the raw materials (slate sintered structural tiles waste), the sintering process, the suitability for processing by powder manufactured by powder technology and the final properties of the end product. The obtained technology results showed that recovered slate waste is a suitable material for use in ceramic tiles, since their properties are within the range of those of conventional ceramic tiles Slate powder waste in ceramics ‘Green’ ceramic pieces from slate powder waste have a potential use using the slip casting process in the manufacturing of ceramic pieces by the slip casting process. Unfired earth bricks (that is, Although currently there is no clear evidence that demonstrate the compressed unfired bricks, use of quarry fines, it is believed that clays and manufactured sand light unfired bricks, unfired clay produced as by-products from the extraction of aggregates could bricks) find application in unfired bricks. Marble and granite reject to Addition of up to 30% (by weight) of non-beneficiated, fine grained enhance the processing of clay and low iron marble and granite reject in red clay based mixture did products not alter the properties of the end product and reduced the firing temperature. Granite sawing wastes in ceramic Granite wastes have physical and mineralogical characteristics similar bricks and tiles to those of conventional ceramic raw materials. The technological characteristics are in agreement with standards for ceramic bricks and tiles. Additions up to 35% (by weight) can be achieved at firing temperatures up to 1200oC.

Reference (El-Mahllawy, 2007)

(Campos et al, 2004)

(Mansur et al, 2006) (GreenSpec, 2007c)

(Segadaes et al, 2005)

(Menezes et al, 2005)

Table 14: Literature findings on the use of quarry fines in heavy ceramic products

4.2.4 CONSTRUCTION PRODUCTS – MANUFACTURED AGGREGATES The production and use of manufactured aggregates, although limited currently in the UK is expected to increase in the future due to changes in legislation and government initiatives, such as the work undertaken by WRAP (The Waste and Resources Action Programme) that promote the specification of good practice recycled content products (WRAP, 2007d). Manufactured aggregates produced using only quarry fines will result to dense products and their end applications is considered limited as primary aggregate sources are readily available at lower cost. However the production of lightweight aggregates is beneficial, because it could assist to the development of lightweight products and at the same time ‘consume’ waste materials and by-products that are currently being landfilled. Technical specifications for lightweight aggregates for concrete are set by BS EN 13055. Part 1 (BSI, 2002d) together with the National Guidance Document PD 6682-4 (BSI, 2003c). Part 2 of BS EN 13055 specifies lightweight aggregates for bound and unbound materials (BSI, 2004b) and it is accompanied by the National Guidance Document PD 6682-5 (BSI, 2005). Research in this area has been active and several trials and projects have been developed that investigated the use of quarry fines in the production of manufactured aggregates. The quarrying of ragstone in Kent produces in excess approximately 200,000 tonnes of poor quality fine grained material and research was conducted to identify the suitability of this material in the production of manufactured aggregates. In the South-East of

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England, only 40% of the aggregate required for construction can be supplied by local sources, which is seen as a driver towards the use of manufacture aggregates. Quarry fines comprises poorly cemented sandstone with high fines content (16.5%) and it has not been found to be suitable for use as an engineering material or as fine aggregate in concrete. Washing the fines could remove the excess fines content and provide an appropriate concrete aggregate, but the installation of a washing plant is expensive. Quarry fines were blended with other solid waste products (namely cement kiln dust, ground granulated blastfurnace slag and pulverized-fuel ash) and were pelletised in a CO2-rich atmosphere. The final products may find potential use as secondary lightweight aggregates, for structural concrete, concrete block manufacture or highways application, if proved suitable through compliance with BS EN 13055 (Padfield et al, 2004). The potential use of quarry fines (<4 mm) combined with recycled plastics for the production of manufactured aggregates was investigated by research. The ‘Plasmega’ process involved the mixing of shredded plastic waste and quarry fines at controlled temperatures to produce lightweight aggregates. A range of different plastics to fines ratios, which varied from 60 to 80% for quarry fines and 20 to 40% for general plastic waste, were used in these trials. Plastic waste was delivered in bales and consisted primarily of general waste (variety of plastic). Contaminants such as wood and metals were separated before and during shredding. Quarry fines consisted of gritstone and limestone, but trial batches were also produced using steel slag, lagoon silt, sand and china clay waste. Fines were added to the mixer first followed by the shredded plastics and combined together at a temperature between 250 to 260oC for 6 to 8 minutes. The mix was fed directly into a briquette plant that produced a 40 mm diameter ovoid, which were subsequently crushed using a hammer mill. Laboratory tests were carried out to determine the properties of the finished product and small scale trials were undertaken of the use of ‘Plasmega’ in asphalt, concrete and block manufacture. Results suggested that from a technical point of view, the process technology appears to be viable and aggregates of consistent quality can be produced for the 50:50 and 60:40 fines/plastic blends of materials. Based on the aggregate abrasion value and the magnesium sulphate soundness value, the produced aggregate is considered a hard and durable material. The polished stone value results especially for the limestone mixes suggested that the manufactured aggregate may not be suitable for surface course material. Asphalt materials containing the lightweight aggregate required an extra binder to achieve full coating and to ensure durability of the material. Overall it was concluded that the ‘Plasmega’ aggregate could potentially be used in asphalt and unbound applications, but further work should be carried out through full scale trials to determine this. The fundamental obstacle to the process was considered to be the ready supply of usable waste plastic at cost appropriate to make the product competitive (Tarmac Ltd and Associates, 2007) (project code: MA 4/2/019). Lightweight aggregates were produced using marine clay and a CaF2-rich semiconductor industry sludge using a bench-scale rotary kiln. The scope of this study was to produce an aggregate source in the area of Singapore, utilising marine clay produced during excavation in construction sites, which is currently treated as waste. Different clay to sludge ratios were trialled (90/10, 70/30, 50/50 (mass %)). All three mixtures showed good bloating behaviour during firing and the ceramic pellets (1 – 1.5 cm diameter) had densities below that required for lightweight aggregates. The water absorption of the aggregates was high due to large pore size, which could be altered by changing the clay to sludge ratio or the firing conditions. Also the composition of the aggregate showed a significant loss of fluorine (40-60%) during processing, but leach testing suggested that aggregates would not pose a human or environmental hazard due to fluorine mobilization. The aggregates were considered suitable for the manufacture of low strength building blocks (Laursen et al, 2006). Clay produced from aggregate quarries could also comprise the binder rather than the

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base material in manufactured aggregates. In other work lightweight aggregates were produced using a rotary kiln by mixing combustion ashes such as pulverized-fuel ash, incinerated sewage sludge ash, municipal solid waste incinerator bottom ash with a binder such as clay (Wainwright and Cresswell, 2000; Wainwright and Cresswell, 2001). Unless energy consumption associated with the production of lightweight aggregates is reduced, the wide use of such materials is expected to be limited as the competition from alternatives such as primary, secondary and recycled aggregates is high. A project currently carried out within the Fifth call of the MIST programme investigates the use of microwave technology to produce lightweight aggregate from quarry wastes, which may result in energy savings. This project is currently underway and it is expected to establish the technical and economical feasibility of microwave processing in the manufacture of sustainable construction materials (The University of Nottingham, 2007) (project code: MA 6/4/006).

4.2.5 HYDRAULICALLY BOUND MIXTURES Hydraulically bound mixtures (HBMs) comprise a combination of aggregates with binder mixtures that set and harden in the presence of water. Hydraulically bound mixtures can employ different types of hydraulic binders and they are therefore classified as Cement Bound Granular Mixtures (CBGM), Slag Bound Mixtures (SBM) and Fly Ash Bound Mixtures (FABM). Cement bound mixtures commonly use Portland cement, whereas slag bound mixtures and fly ash bound mixtures utilise granulated blast furnace slag (and depending on mixture type also include partially ground granulated blast furnace slag and ground granulated blast furnace slag) and fly ash respectively as the binder phase. Hydraulically bound mixtures find application in road (major, minor roads) and paving construction (paved areas, heavy duty paving), in shore and slope protection, flood protection, dams, liners, container embankment structures, river/canal bank protection and backfill. In pavement construction, HBMs can find application in base, subbase and capping layers. Quarry fines could be utilised as an aggregate or in the production of alternative binders (for example, in composite cement), material below 4 mm could find application as fine aggregate in HBMs. Technical specifications on aggregates for hydraulically bound mixtures are given by BS EN 13242 (BSI, 2002b) and the accompanying National Guidance document PD 6682-6 (BSI, 2003b). The European Standard sets specific requirements for the geometry, physical, chemical and durability properties of aggregates, a summary of which is shown in Table 15. The Manual of Contract for Highways Work,Volume 1 and Series 800 (Highways Agency, 2007a) sets the requirements for hydraulically bound materials used in road pavement. According to Specification for Highway Works, china clay and slate waste is included in the list of alternative materials that could be used as aggregates, whereas the use of quarry fines may be considered by the Overseeing Organisation on a site specific basis. Also the Interim Advice Note 73/06 (Highways Agency, 2006) provides guidance on the construction of road pavement foundations and has to be applied during all road construction, implementation, improvement and maintenance works. The European Standards for HBMs are divided into two main series, the BS EN 14227 series (BSI, 2004c), which covers specifications for hydraulically bound mixtures and the BS EN 13286 series which cover test methods for HBM (BSI, 2003d). The use of sandstone quarry sand (SQS) in cement bound road subbase was investigated. Physical data suggested that the material would form a good subbase in of strength and compaction. The sandstone quarry sand could comfortably meet the specification for a cement bound subbase (CBM 1). Four different mixes utilising 50, 75, 100 and 125 kg/m3 cement contents based on a density of 2,200 kg/m3 were prepared and test cubes were compacted at moisture content of 9% by mass of aggregate. Results suggested that

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blocks displayed a steady increase in compressive strength with cement content. The 4.5 N/mm2 requirement for CBM1 was satisfied for materials with cement content falling between 75 and 100 kg/m3. Also, the 7 day compressive strength of 4.5 N/mm2 would be achieved by materials with 100 kg/m3 cement content and by adding approximately 4% of cement to SQS (Lamb, 2005). The utilisation of recycled and secondary materials in hydraulically bound mixtures has been studied in the past (Dunster et al, 2005a; Dunster et al, 2005b). Alternative materials such as silt dredging, pulverized-fuel ash, clay and steel slag fines were trialled in applications that involved stabilisation for erosion protection and in road construction and paving (Dunster et al, 2005b). The advantages seen from using alternative materials in HBM were end product related (such as, higher strength was achieved), economic (for example, avoid disposal cost or transport of primary aggregates), environmental (such as, reduced pollution associated with transport) and operational (such as, easy to handle and use). Technical guidance on the use of alternative materials in HBMs for different applications such as in major road or minor road construction, erosion protection, liners and heavy pavement was produced within this project (Dunster et al, 2005c; Dunster et al, 2005d; Dunster et al, 2005e). The referenced case studies provide some good examples of utilisation of alternative materials in HBM and it is anticipated that similar benefits could be achieved by using quarry fines. Research is currently being undertaken within the MIST programme (sixth call – Thematic Value: Optimising Resource Value) on the use of quarry dust in hydraulically bound mixtures for construction applications. The scope of this project is to carry out a detailed literature review of existing studies, to develop specifications for HBMs with quarry fines in their structure, to undertake laboratory investigation and to produce a guidance document and technical report which will include all project findings. It is anticipated that this project will be completed during 2008 (Scott Wilson, 2007) (project code: MA 6/4/003). BS/EN standard Properties requirement Geometrical Grading

Applicable to/ methodology Coarse, fine and all in aggregates (determines sieve apertures; break point between coarse and fine aggregates = 4 mm)

Crushed and broken Coarse aggregates (assesses the potential for mechanical interlock between the surfaces coarse aggregate particles; in accordance with BS EN 933-5:1998 (BSI, 1998) Fines content

Physical

Chemical

Resistance to fragmentation

Coarse, fine and all-in aggregates (percentage ing a 63 µm sieve; the Specification for Highway Works however specifies a 75 µm sieve; adopted category will be determined from end use) Los Angeles test

Resistance to wear

Coarse aggregate (Micro-Deval test)

Particle density

In accordance with BS EN 1097-6 (BSI, 2000b)

Acid-soluble sulfate

Applicable to blast furnace slag aggregate only

Total sulfur

Low content in aggregate sources in the UK, so unless stated this is not applicable

Constituents which Commonly not applicable in the UK alter the rate of setting and hardening of hydraulically bound mixtures Durability Based on water In the UK, aggregates are considered satisfactory without further testing if they absorption value conform to water absorption WA242. Aggregates with water absorption above 2% should satisfy general purposes uses if they conform to the magnesium sulfate soundness category MS Table 15: Requirements for aggregates for hydraulically bound mixtures35in accordance with BS EN 13242 (BSI, 2002b)

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The use of quarry fines is under investigation by Scott Wilson and Transport Research Laboratory. This project is due to be completed in 2008 (Scott Wilson and TRL, 2007). The objective of this project is to characterise a range of different quarry fines, with and without hydraulic binders, and to develop procedures for the use in pavement engineering. (Scott Wilson and TRL, 2007). Further information and case studies on the use of quarry fines in hydraulically bound mixtures can be found elsewhere (Manning, 2004; Zoorob et al, 2002).

4.2.6 ASPHALT APPLICATIONS Quarry fines may be used in asphalt paving and surface treatment as fine aggregate or/and filler. Technical requirements for aggregates used in asphalt are covered by BS EN 13043 (BSI, 2002e) with the ing document PD 6682-2 (BSI, 2003e). According to BS EN 13043, fine aggregate suitable for asphalt comprise the particle size fraction below 2 mm and as filler, the aggregate most of which es the 63 µm sieve, which can be added to construction materials to provide certain properties. A summary of requirements for aggregates used in asphalt according to BS EN 13043 is shown in Table 16. The Specification for Highway Works, Series 900 sets the requirements for bituminous bound materials used in road pavement construction (Highways Agency, 2007). Also technical standards such as the BS EN 12697 (part 11) (BSI, 2000c) specifies the compatibility between aggregate and bitumen and the BS EN 13179 (BSI, 2000d) describes testing for filler aggregate used in bituminous mixtures. By the beginning of 2008, new European Specifications for asphalt, its constituents, and methods of testing will be introduced (QPA, 2007b). BS/ EN standard Properties requirement Geometry Grading Fines content

Physical

Durability Chemical

Resistance to fragmentation Resistance to polishing of coarse aggregate for surface courses Resistance to surface abrasion Soundness Coarse lightweight contaminants Requirements for filler aggregate

Applicable to/ methodology Coarse, fine and all in aggregates; break point between coarse and fine aggregates = 2 mm Fine aggregate (percentage ing a 63 µm sieve; the methylene blue test is not considered sufficiently precise in the UK; compliance with the fines content limit or evidence of satisfactory use is required instead; in British Standards a 75 µm sieve is specified) Los Angeles test Coarse aggregates (In accordance with BS EN 1097-8 (BSI, 2000e); guidance on minimum polished stone values is given in the Highways Agency Design Manual For Roads and Bridges (Highways Agency, 2004) Measurement of the aggregate abrasion value (in accordance with BS EN 1097-8) (BSI, 2000e) The magnesium – sulfate soundness test is recommended Testing is recommended for recycled aggregates only Recommended tests: particle size distribution and loose bulk density in kerosene in accordance with BS EN 13043 (BSI, 2002e)

Table 16: Requirements for aggregates for asphalt and surface treatment (BSI, 2002e)

The use of quarry fines as aggregate or filler for asphalt has been investigated by research, and where possible, such materials are utilised. A good example is the use of china clay waste in the A30 Bodmin to Indian Queens dual carriageway, where approximately 800,000 tonnes of material have been utilised for the new road and asphalt layers. The use of china clay waste reduced the demand for primary materials, minimised the pollution from long distance transport of quarried stone, as well as reduced the associated

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costs, and provided social benefits such as less nuisance to local communities from transport, and employment opportunities (Highways Agency, 2007b). The REFILL project, funded by the EU BriteEURam programme, investigated the use of quarry fines from the sandstone Leadhill Quarry (Scott Wilson Ireland) in various end uses including asphalt. Assessment work was focused on incorporating 0-2 mm fines in typical surface (wearing) course asphalt mixtures and subsequently examined impact durability. Results suggested that the mixtures are not suitable due to the high filler content (~23%). Additional testing with blends of fines with 3 mm single size aggregates provided satisfactory results due to the lower filler content of these mixtures (Mitchell et al, 2004). According to the International Center for Aggregates Research, the physical and chemical properties of fine material are critical when utilised in applications such as hot-mix asphalt. In particular properties such as surface free energy, chemical interaction potential, surface area and aggregate shape characteristics (angularity and texture) can impact the adhesive bond between the aggregate and binder. Testing trials were undertaken with a variety of combinations of bitumen and aggregates for determining mixtures’ performance, whereas the influence of aggregate shape was evaluated by modelling techniques (Bhasin and Little, 2006; Masad et al, 2004). Several other research projects examined the use of quarry fines as well as recycled and secondary aggregates in asphalt and bituminous mixtures. A summary of the outcomes of these projects is shown in Table 17. Project Evaluation of marble waste dust in the mixture of asphaltic concrete Use of aggregates produced from marble quarry waste in asphalt pavement

Case Study – A316 resurfacing project

Development of bitumenbound waste aggregate building blocks

Exploitation and use of quarry fines

Findings Use of marble dust as filler material. Optimum filler/ bitumen content was obtained and results suggested that marble dust can be used (unprocessed in asphalt mixtures) Marble and andesite quarry wastes were compared with conventional materials for use as aggregates in asphalt pavement. The physical properties of the aggregate were found to be within specified limits and they could potentially be used in light to medium asphalt pavement binder layers Use of recycled aggregates such as glass and incinerator bottom ash (IBA) in a resurfacing pilot project. Recycled aggregates replaced the fine aggregate in asphalt. The recycled glass and IBA performed well. Materials were found to be highly consistent and comparison with primary materials gave good results Use of pulverized-fuel ash, incinerated sewage sludge ash and steel slag for the development of bitumen–bound blocks (Bitu-blocks), which are made by 100% recycled aggregates. Compressive strength results were at least equal to concrete blocks and appeared to be more stable than conventional masonry blocks. Literature review report presenting several other examples

Reference (Karasahin and Terzi, 2007) (Akbulut and Gurer, 2007)

(Transport for London, 2005)

(Forth et al., 2006; Van Dao, 2006; Zoorob et al, 2002))

(Manning, 2004) (project code MA 2/4/003)

Table 17: Literature findings on the use of quarry fines and alternative aggregates in asphalt applications

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4.3 SUMMARY OF POTENTIAL UTILISATION ROUTES FOR QUARRY BYPRODUCTS In Section 4, several end uses, which could potentially be applicable to quarry fines, have been discussed. These include the use of quarry fines in unbound and bound applications. As mentioned earlier in this report, quarry fines are most often economically used for restoration purposes, but a fraction of these materials remain unused and the objective of this report is to identify potential end uses for these materials. A summary of the trends identified in Section 4 is given in Table 18 (a and b). End Use

Specifications

Quarry restoration Backfill/infill of voids General fill (i.e embankments) Road pavement construction (i.e sub-base, capping)

Remediation; artificial soils; compost

Filler applications (for example, paper, paint, plastics, rubber) Portland cement – kiln meal

BS EN 13242 (BSI, 2002b) BS EN 13242 (BSI, 2002b) Specifications for Highway Works–Series 600 and 800 (Highways agency, 2007a) BSI PAS 100 BS 3882

European Standards on fillers’ critical properties

Type of quarry byproducts *1 Type 1 and Type 2 (and often inert waste from secondary sources) Type 1 and Type 2

Current level of exploitation *2 In use – predominant end use In use (in a few projects) In use if found locally / Trials In use if found locally / Trials

Utilisation potential *3 High volume – low value

Type 1 and Type 2

In use in some areas

High volume – low value

Type 2

Trials with Low volume mineral residues – high value of calcareous and siliceous composition Trials/In use Medium to Substitution of primary high volume - materials medium value

Type 1 and Type 2 Mainly Type 2–Type 1 in certain circumstances (such as high consistency material)

BS EN 197 (BSI, 2000a)

High volume – low value High volume – low value High volume – low value

Benefits Re-use of overburden material and production residues Use of large volumes of quarry fines Minimisation of exploitation of primary aggregates Less pollution produced from the production and transport of primary aggregates Enhance plant growth; soil fertility; added nutritional value Minimisation of quarry residues Environmental and social benefits seen from enhanced health of soils and plants Low cost fillers

Type 2 and Type 1 (in certain circumstances (for example, high consistency material) Innovative Green Type 2 and Type 1 (in Not in use Low volume Low cost primary products (for specifications certain circumstances – high value materials example, green design guides (for example, high roofs, eco-slates, consistency material, cob building ) composition) (*1)à Mineral by-products classification as determined by REFILL research project – check Table 1 for further information (*2)à Based on literature review findings (*3)à Term Volume refers to quarry fines volumes potentially utilised; term Value corresponds to end use Table 18a: Summary of potential end uses for quarry fines

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Controlled low strength materials – self compacting concrete Manufactured concrete

Heavy ceramics

Specifications

Type of quarry byproducts *1 BS EN 12620 (BSI, Type 1 and Type 2 2002a)

Current level of Utilisation exploitation *2 potential *3 Trials High volume – low value

BS EN 12620 (BSI, Type 1 and Type 2 2002a); BS EN 206 – 1 (BSI, 2000f); BS 8500 (BSI, 2006a; BSI, 2006b) BS EN 771–1 (BSI, Type 1 and Type 2 2003i)

In use (if found Low volume locally)/trials – low to medium value (depending on end product) In use/trials Low volume – low to medium value Trials/In use Low volume – medium to high value

Manufactured aggregates


End Use

Benefits

Substitute of natural sand/ aggregate

BS EN 13055 (BSI, Type 2 and Type Minimisation of quarry 2002d; BSI, 2004b) 1 in certain residues circumstances Reduced exploitation of (such as material primary aggregates consistency) Hydraulically BS EN 13242 (BSI, Type 2 and Type Trials/In use Low volume If sourced locally, bound mixtures 2002b) 1 in certain – low to circumstances medium value reduced emissions/ pollution from transport (such as high consistency material) Asphalt BS EN 13043 Type 2 Trials/In use (in Low volume (BSI, 2002e); certain cases) – medium Specifications for value Highway Works - Series 900 (Highways Agency, 2007a) (*1)à Mineral by-products classification as determined by REFILL research project – check Table 1 for further information (*2)à Based on literature review findings (*3)à term Volume refers to quarry by-products volumes potentially utilised; term Value corresponds to end use Table 18b: Summary of potential end uses for quarry by-products

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5 BARRIERS TO UTILISATION Quarry fines can be suitable materials for a variety of end applications; however, currently their utilisation is not widespread to the level it would have been expected mainly due to reasons related to the geographical position of quarries. Very often quarries operate in remote location from potential end s and the cost of material to them includes high transport costs, which discourages their use. A good example of the effect of transport cost to utilisation is the china clay by-products in Cornwall, which although they represent a suitable material for various end product, their use has been limited to local markets only. A case study of china clay sand is given in Figure 8, which presents in detail the drivers and constraints associated with the sustainable use of these materials. There are occasions where producers of aggregates are not aware of potential utilisation routes for their quarry fines in the local area, and these materials remain unused. The principles of industrial ecology and industrial symbiosis could prove beneficial in such cases for identifying markets in close geographical proximity that can absorb these materials. Government initiatives like the National Industrial Symbiosis Programme (NISP), aim to assist the industry to develop linkages and synergies between businesses in a local/ regional level and this way to turn unutilised material into a resource. Another obstacle, reported by research, is the application of the Aggregates Levy to quarry fines (Manning, 2004; The University of Leeds, 2007d) (project code MA 2/4/003). End s decide what materials will be incorporated into their manufacturing process primarily upon economic criteria. If a secondary material offers essential elements to the end product or manufacturing route and at the same time provides a profit to the end by reducing the cost of the feedstock or contributing other benefits, for instance environmental (reduced emissions) or technical (desirable performance), then this material will be considered as a valuable substitute for primary materials. Quarry fines are found in competition at the same time with primary and alternative materials. Certain advantages can be seen however in quarry fines compared to other secondary materials. Quarry fines are considered more consistent materials in relation to their composition and particle size, also over time (temporal variability), they are commonly inert or non-hazardous which means that their impact to the environment and human health is very low, and they could provide some degree of security to the end in of stable material supply. Often quarry fines require some degree of processing before they can be used, which may increase their cost and at the same time requires suitable infrastructure and equipment to become readily available. Quarry fines from aggregate and sand and gravel production are not exempt from the Aggregates Levy and therefore the use of such materials in construction products does not count towards recycled content. Current legislation such as the Waste Framework Directive and sustainability strategies (for example Strategy for Sustainable Construction (BERR, 2007)) aim to promote resource efficiency and the use of recycled/reclaimed materials (for example, set minimum requirements for recycled content in construction), which drive construction product manufacturers to utilise secondary materials in their products. This driver

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to supply on products containing increased recycled content s the use of recycled and secondary aggregates, and investment and technical inventions to enable these uses. This driver does not apply to quarry fines. Another important obstacle to utilisation is the limited knowledge of exact quantities of quarry fines. Currently only estimated quantities are available, which are calculated using a waste to mineral ratio. According to DEFRA, during 2003 approximately 34 million tonnes of quarry waste were generated, based on a waste to product ratio equal to 1 to 9. DEFRA does not provide an accurate definition of quarry waste hence it is not clear what proportion of the reported figures corresponds to quarry fines, or whether it includes other materials such as overburden. Past research estimated the percentages of fines generated from different rock types and following this methodology the total production of fines from quarrying using the 2005 Aggregates Mineral Survey was 28.4 million tonnes (Table 7). The estimation of quarry fines production given in Table 7 is considered more relevant in this report, as it is an estimate of overall fines production, but it is not possible to quantify the fraction of these quarry fines that may be excess to market demand. Taking as example the utilisation of alternative materials used as aggregates, it can be seen that they have progressed considerably, in part due to the availability of information on sources, tonnages, temporal variability and consistency. It is recommended that figures on quantities of fines produced, marketed and stockpiled should be calculated in order to properly evaluate the quantities of quarry fines currently available, and information that present the geographical distribution of quarry fines, should be compiled to enable the identification of potential end markets. Information on the characteristics of quarry fines (such as, particle size, mineralogy) from different quarry operations is not available and this is seen to affect the marketability of these materials. A past European project (REFILL) carried out research which identified the characteristics of quarry fines. However, this information is difficult to locate, which prevents this project from the assessing the quality and consistency of those data, and makes it impossible to decide if they should become publicly available. Very often barriers to the use of quarry fines are due to the absence of fit-for-purpose specifications. Although technical standards, such as the European Standards on aggregates have broadened their scope to include secondary and recycled materials, they are not always considered as fit-for-use by the industry. For instance, the use of grading specifications to determine aggregates for concrete will exclude very fine material (below 63 µm), because it is not common practice in the UK to use filler aggregate in concrete and more importantly it is not required to determine the composition of fine and filler aggregate. Compositional characterisation and suitable classification tests can easily identify adverse constituents such as clay or shale into quarry fines and thus determine whether their incorporation into the final product is feasible. Grading specifications cannot provide this kind of knowledge and currently in the UK only compliance with the fines content limit is required. Another example is the use of quarry fines and dust in soil remineralisation and composting. Uncertainty over the acceptability of compost containing rock dust in respect with the BSI PAS 100 has become apparent as the deliberate addition of non-biodegradable feedstock (for example, sand and gravel) is not allowed unless sufficient evidence to demonstrate an enhancement of the process is presented (Szmidt and Ferguson, 2004).

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Case study: Promoting the use of china clay waste China clay waste is produced from the extraction of kaolin from decomposed granite. The waste to product ratio is 9:1 in china clay quarries Locations of china clay quarries: Cornwall (St Austell), Devon (Lee Moor, South Devon) Composition of china clay waste (in relation to 9:1 waste to product ratio): n sand (4 tonnes) n stent (2.5 tonnes) n overburden (1.5 tonnes) n fines (1 tonne) Arisings n Overall arisings: 19.6 Mt n Potentially available (estimated aggregate resources from ‘live feed’ operations): 7 Mt/year n Potentially available (estimated aggregate resources from existing stockpiles): 156 Mt/year n Aggregate resources in use: 2.6 Mt/year Current use Predominantly in the South-West, which has a finite requirement for such aggregates. Several other end uses have been investigated and found suitable (such as, aggregates for concrete, bulk fill uses etc) Drivers to utilisation n Legislation and government initiatives the use of secondary aggregates: for example, exemption of china clay waste from Aggregates Levy; landfill tax; sustainability issues (such as, sustainable construction strategy and the promotion of use of materials with recycled content, sustainable use of natural resources); EU Mining Waste directive; EU Communication on waste and by-products n Existing standards and specifications are in place: for example Specifications for Highway Works Series 800, 900 and 1000 permit the use of china clay sand; BS13242 on aggregates for unbound and hydraulically bound materials, BS EN 12620 on aggregates for concrete and so on n There is a significant supply of china clay waste and a high potential for aggregate use n There is a significant market for sand and gravel, which china clay aggregate could meet n Shipping or pumping seems as economically viable solution for transporting china clay waste n Landscape, habitat and environmental benefits to be seen from removing this waste Barriers to utilisation n Transport of china clay waste remains a significant obstacle to utilisation n If pumping of china clay becomes the preferred route for transport, then additional installations and infrastructure requirements will have to be developed with additional economical cost. Future work requirements n Resolve the problem associated with the transport of china clay waste. Pumping and shipping both look as potential solutions n Further research is required in establishing the suitability of china clay waste for certain end uses (for example, in concrete) n Developing a Quality Protocol for china clay waste is expected to promote utilisation n Developing a marketing plan for china clay waste n Conducting detailed feasibility studies on the true capital and operational costs associated with aggregate pumping

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6 CONCLUSIONS

This report focused on quarry fines produced from aggregates and sand and gravel production. Quarry fines and dust are generated from various activities such as extraction (for example drilling and blasting) and rock preparation / beneficiation. Quarry fines below 6 mm may be included in an end product (for example, Type 1 aggregate), be a product in their own right (for example, fine aggregate) or be surplus to market demand, namely excess fines which remain unused. The fines may include a high proportion of ultra fine (dust) particles (below 75 µm), which may also be part of an aggregate product, or be produced in excess, or be produced as a by-product. Definitions that properly describe all these different fractions do not currently exist; it is considered essential that the industry establish robust definitions in order to provide a clear language with which to discuss and communicate the issues relevant to quarry fines. The current European standards on aggregates provide some fit-for-purpose criteria for aggregate materials, which are primarily based on grading but are applied to all aggregates, wither recycled, secondary or primary. Therefore, as fine aggregate is determined the fraction of material below 4 mm for use in concrete, mortar, unbound and hydraulic bound applications and below 2 mm for inclusion in asphalt products. There is still a need to develop better fit-for-purpose specifications that take into the nature of different materials, market trends and economics in conjunction with criteria currently used by end and available technical standards. Figures on available resources and quantities of quarry fines are based on estimates rather than real data and this is considered as a substantial barrier towards utilisation. This report investigated the potential use of quarry fines in both unbound and bound applications. The primary utilisation route for quarry fines is in restoration work. However, not all of quarry fines are used for restoration, and in certain cases they may exhibit suitable properties for a variety of other end uses with an associated profit for the aggregate producer. Literature findings have shown that quarry fines are suitable materials for use in bulk fill applications (for example, backfilling, infilling, general fill), in road pavement construction, in remediation and for the production of artificial soils and compost. All the above end uses are partially in use, depending on availability of resources in geographical proximity. Other end uses such as fillers in paper and paint or the use of quarry fines in Portland cement have been trialled or have been used on single occasions. Also, the inclusion of quarry fines in innovative products (such as, green roofs, cob building) has not been implemented as yet. Bound applications reviewed in this report include various construction products (such as, concrete, heavy ceramics, manufactured aggregates), in flowable fills, in hydraulic mixtures and asphalt. Trials have been undertaken for all these different applications and some of them are in use in individual cases.

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The location of quarry fines, the limited awareness of aggregate producers for potential markets, the competition with primary and alternative materials, the limited knowledge about quarry fines arisings and the characteristics of these materials, and the absence of properly developed fit–for–use specifications are some of the barriers to utilisation identified through this project. Future research work should address and try to find solutions to constraints identified. Further information for future research work is presented in Section 7.

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7 RECOMMENDATIONS FOR FUTURE WORK This project has addressed the sustainable utilisation of quarry by-products in a variety of applications. The review process has identified certain gaps of knowledge that should be covered by future research work. These are highlighted in the bullet points following: n Mapping quarry fines: It is considered essential to determine the quantities of quarry fines, in order to promote sustainable utilisation. The classification of quarry fines arisings into produced, stockpiled and marketed would enhance current knowledge regarding the percentage of such materials which remains unused. Also it would be useful to develop a ‘live’ system, such as a GIS database, which will display the geographical distribution of quarry fines across the UK. n Feasibility studies for quarry fines. The development of detailed feasibility studies for specific material streams will provide an insight to the technical and economic viability of different utilisation routes. Although feasibility studies tend to be case specific, they assist to increase awareness for issues specifically relevant to different rock types (such as, sand and gravel, hard rock). n Characterisation of quarry fines. Critical characteristics of quarry fines such as mineralogy, particle size, compositional consistency, temporal variability and storage and handling properties should be addressed for a variety of different products. The availability of such information is expected to assist the match making process between quarry fines and utilisation routes and to assist the initiation of synergies between aggregate producers and end s. n Development of ‘good practice guides’ for the utilisation of quarry fines into different applications. These should include examples from current utilisation practices and refer to critical requirements that should be met for the incorporation of quarry fines and dust into different end products.

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REFERENCES ALSF FUNDED REFERENCES MA 6/4/012. Birmingham University (2007). Monitoring of remediated acidic sites using quarry wastes. URL . Access date:[15/12/2007]. MA 1/3/003. Guillou, G. and Davies, R. (2004). Combination of basaltic quarry fines with organic process residues for the development of novel growing media. URL< http://www.mi-st.org.uk/research_projects/ final_reports/final_report_ma_1_3_003.pdf>. Access date: [15/12/2007]. Mineral Solutions Ltd. MA 4/2/002. Jeffrey, C.A, Hill, I.A and Fitch, P.J. (2003b). Waste minimisation by the application of integrated technology. URL< http://www.mi-st.org.uk/research_projects/final_reports/final_report_ma_4_2_002.pdf>. Access date: [15/12/2007]. Department of Geology. University of Leicester. MA 3/2/001. Jeffrey, K., Eddleston, M. and Bailey, E. (2003a). Aggregate deposits and processing simulation to optimise waste utilisation (AGSIM). URL< http://www.mi-st.org.uk/research_projects/final_reports/final_ report_ma_3_2_001.pdf>. Access date:[15/12/2007]. Department of Geology. University of Leicester. MA 3/2/002. Jeffrey, K., McKee, G. and Bailey, E. (2004). Sand and gravel aggregate deposits-improved characterisation technology (ADICT). URL< http://www.mi-st.org.uk/research_projects/final_reports/final_ report_ma_3_2_002.pdf>. Access date:[15/12/2007]. Leicester University and Tarmac Southern. MA 2/4/003. Manning, D. (2004). Exploitation and Use of Quarry Fines. Manchester: Mineral Solutions. Report No. 087/MIST2/DACM/01. URL< http://www.mi-st.org.uk/research_projects/final_reports/final_report_ma_ 2_4_003.pdf>. Access date: [15/12/2007]. MA 4/5/003. Mitchell, C. (2007). Quarry Fines Minimisation. URL< http://www.mi-st.org.uk/research_ projects/final_reports/final_report_ma_4_5_003.pdf>. Access date: [18/12/2007]. British Geological Survey, Nottingham. MA 4/5/002. Mitchell, C. (2007b). Waterless fines removal. URL<: http://www.mi-st.org.uk/research_projects/ final_reports/final_report_ma_4_5_002.pdf>. Access date:[18/12/2007]. British Geological Survey. MA 6/4/003. Scott Wilson (2007). The use of quarry dusts in hydraulically bound mixtures for construction applications - Summary. URL< http://www.mi-st.org.uk/research_projects/summeries/proj_sum_ma_6_4_ 003.pdf>. Access date:[17.10.2007]. MA 4/5/009. Smith, R.A., Sowerby, C., Knapman, D., Myall, D., May, J., Lewis, R., Bamfield, B. and Fox-Davies, T. (2005). Feasibility of china clay secondary aggregate use. URLhttp://www.mi-st.org.uk/research_projects/final_ reports/final_report_ma_4_5_009.pdf. Access date:[17/10/2007]. TRL Limited.

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MA 4/2/019. Tarmac Ltd and Associates (2007). Management and Re-use of Quarry Assets. URL< http://www. mi-st.org.uk/research_projects/final_reports/final_report_ma_4_2_019.pdf>. Access date:[17.10.2007]. University of Leeds (2007a). Goodquarry. URL , Access date:[31-AUG-2007]. MA 2/3/007. University of Nottingham (2003). Cleaner Quarries: optimising environmental performance.. School of Chemical, Environmental and Mining Engineering. University of Nottingham. URL< http://www.mist.org.uk/research_projects/final_reports/final_report_ma_2_3_007.pdf>. Access date:[17.12.2007] MA 4/1/002. University of Nottingham (2005). Cleaner Quarries: Methods to reduce the environmental impact of quarry operations. School of Chemical, Environmental and Mining Engineering. University of Nottingham. URL< http://www.mi-st.org.uk/research_projects/final_reports/final_report_ma_4_1_002.pdf>. Access date:[17/12/2007]. MA 6/4/006. University of Nottingham (2007). Using microwave technology to produce lightweight aggregate from quarry waste. URL ; Access date:[12/10/2007].

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APPENDIX APPENDIX I: PAST RESEARCH MIST PROJECTS Project title China Clay Secondary Aggregates Feasibility and Demonstration Programme Combination of basaltic quarry fines with organic process residues for the development of novel growing media Development of an interactive database to enhance the exploitation of quarry fines. A Generic Model for the Formulation of Growing Media from Composts and Quarry Fines

Project holder

Project programme

Project code

Imerys Minerals

MIST

MA/4/5/009

Mineral Solutions Ltd

MIST

MA/1/3/003


MIST

MA/2/4/003


MIST

MA/3/1/003

Table 19: Past research projects undertaken within the Mineral Industry Sustainable Technology Programme

APPENDIX II: THE INTERPRETATIVE COMMUNICATION ON WASTE AND BY-PRODUCTS (COM (2007) 59 FINAL)

Is the intended use of the material lawful?

Material is a waste No

Yes

Then material is a product, not a production residue

Yes

Was the material deliberately produced? (Was the production process modified in order to produce the material?) No Material is a production residue - tests below apply

Criteria 1

Is use of the material certain?


Yes Criteria 2


Yes

Criteria 3

Then the material is a non-waste by-product

Is the material ready for use without further processing (other than normal processing as an integral part of the production process?

Yes

Is the material produced as an integral part of the production process?

No

Material is a waste

Figure 9: A decision tree for waste versus by product decision (Commission of the European Communities, 2007)

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Criteria 1

Only a proportion of the material has a guaranteed use

Is the material not useable? OR

Yes

Does it not meet technical specifications? OR

Material is going to be stored for indefinite time prior to potential (not certain) reuse

No Yes

Waste (*)

Is there no market present for this material? Yes

Waste

No

No

Waste

Go to Criteria 2

*until further changes are identified (i.e long term contracts) additional parameters to be taken under consideration

Figure 10: Decision tree for criteria 1 (in accordance with the Interpretative Communication on waste and by-products (COM (2007) 59 final (Commission of the European Communities, 2007))

Criteria 2&3

Can the material be used without any further processing?

An additional recovery process is required

No

Yes Material is a waste until this process is complete

Go to Criteria 3 Are tasks performed as integral part of the continuing process of production? Yes

Yes

Material is a by-product after investigating the following: n Degree of readiness of material for further use n The investigation of processing/ recovery tasks into the main production process n Whether tasks are carried out by someone other than the manufacturer

Figure 11: Decision tree for Criteria 2 and 3 (in accordance with the Interpretative Communication on waste and byproducts (COM (2007) 59 final (Commission of the European Communities, 2007))

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Case Study – Leftover rocks from mining and quarrying – The AvestaPolaris case (I) Facts on the operation n The activities of AvestaPolarit Chrome Oy consist in extracting chromium-rich ore and producing chromium concentrate. n Within one year of extraction 8 million tonnes of leftover rock is generated. n About 100 million tonnes of leftover rock are already stored around the mine Potential end uses of leftover rock n Backfilling parts of the mine – stacks will be landscaped prior to use n A small proportion, about 20% will be processed into aggregates n Stacks already stored may be used as filling material in constructing breakwaters and embankments Diary of actions n AvestaPolarit applied for an environmental licence to enable the continuity of mining and processing activities on site (gradual changes took place from open-cast activities to underground mining) n Environment centre granted licence, but classified leftover rock and ore-dressing sand as waste, because production residues are not immediately reused or consumed. n AvestaPolarit appealed against that decision Questions set to the Court Are production residues (leftover rock and ore-dressing sand) from mining operations to be regarded as waste in accordance with Directive 75/442/EEC on waste (The European Parliament and the Council, 1975) and having recard to points: n Place production residues are stored (i.e mining site, ancillary site, other) n Composition of production residues (i.e leftover rock is of similar composition to primary ore) n Health and safety impacts (i.e leftover rock is harmless to human health and the environment) n Potential reuse and no intention to discard such materials Court’s reply Answers to question 1: n Leftover rock stored for an indefinite length of time to await possible use/discard is classified as waste (Palin Granit Oy, 2002) n The place of storage, composition or proof that residues do not pose a threat to human health or the environment, are not relevant criteria for determining whether leftover stone is to be regarded as waste (Palin Granit Oy, 2002) n Foreseeable reuses, such as in the construction of harbours, in embankment work or for inclusion in construction products do not represent a certainty and leftover rock should be regarded as waste n Leftover rock processed into aggregates, even if such use is probable, it requires an operation for recovery of the desirable fraction, which does not comprise part of the production process and residues therefore should be classified as waste n Stacks of materials that remain on site will also constitute a waste, as no certain use without requiring processing exists. Landscaping of such materials represents an environmental friendly manner of dealing with them, not a stage in the production process n Where leftover rock is intended to be used for filling in the galleries of the mine and sufficient evidence is in place as to the identification and actual use of the substances, then they would not be waste. n The term by-product should be confined to situations in which the reuse of the goods, materials is not a mere possibility, but a certainty, without further processing prior to reuse and as an integral part of the production process

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APPENDIX III: FIT- FOR- PURPOSE REQUIREMENTS Product sector

Ceramic products

Role of alternative material (source/ ingredient) Clay substitute Body fuel Filler Particle size sand Colourant

Cement

Concrete

Insulation

Manufactured aggregates

Fluxing agent For use in kiln meal Ca-rich source Si-rich source Al-rich source Fe-rich source Si+Al+Fe source Ca+Si+Al+Fe source For the production of blended cements Pozzolanas Hydraulic materials Reactive phase Coarse aggregate Filler aggregate Cement pigments Fuel Formstone Flux Primary rock Base filler Binder Fuel Bloating agent Fluxing agent Coating

Critical properties on alternative materials Examples of materials

Particle size, plasticity, firing temperature, colour after firing Calorific content

Common clay, fireclay

Aesthetic properties (colour, texture), scumming, efflorescence Reactivity temperature, particle size

Water-ochre colliery waste

Chemistry, particle size, loss on ignition Chemistry, particle size, loss on ignition Chemistry, particle size, loss on ignition Chemistry, particle size, loss on ignition Chemistry, particle size, loss on ignition Chemistry, particle size, loss on ignition

Limestone fines Sand Residues from bauxite mining Water colliery waste Quarry fines (various) Quarry fines

Chemistry, specific surface area Chemistry, particle size

Natural pozzolanas, silica four Ground granulated blast furnace blast Limestone, gypsum aggregates Quarry fines Portland cement, blended cement Iron oxides coke Waste material from mineral wool production Blast furnace slag Basalt, gabbro Quarry washings

Chemistry Particle size Particle size

Chemistry, particle size Chemistry, particle size Chemistry, particle size Chemistry, particle size Mineralogy, chemistry, particle size, moisture content, loss on ignition (%) Mineralogy, chemistry, particle size, moisture content, loss on ignition (%) Mineralogy, chemistry, particle size, moisture content, loss on ignition (%) Mineralogy, chemistry, particle size, moisture content, loss on ignition (%) Mineralogy, chemistry, particle size, moisture content, loss on ignition (%) Mineralogy, chemistry, particle size, moisture content, loss on ignition (%)

Colliery spoil, coal fines

Fine silica sand

Cement Colliery spoil Municipal solid waste fly ash Fine glass, fine silica sand

Table 20: Characterisation framework and fit-for-purpose requirements for the use of alternative materials in ceramics, cement, concrete, insulation and manufactured aggregates products (MIRO, 2007)

78


APPENDIX IV: TECHNICAL SPECIFICATIONS FOR MANUFACTURED CONCRETE PRODUCTS Concrete application Precast concrete drainage units

Product Channel Manholes and inspection chambers Pipes Precast concrete floor elements Ribbed floor; ribbed floor elements Precast concrete landscaping and Block paving Edging hard surfacing units Flags Street furniture Precast masonry units Autoclaved aerated concrete Block Brick Cast stone and reconstructed stone masonry Capping Edging Lintel Manufactured stone masonry unit sills Precast concrete linear units Beam Column Frame unit

Precast flooring units

Precast concrete road and hard surfacing unit

Precast concrete roofing system units Precast structural units

Staircase unit Beam and block Composite lattice girder Composite solid slabs Floor plates for flooring systems Hollow core Hollowcore Staircase unit Block paving Channel Kerbs Quadrant Floor plates for flooring systems Roof tiles and fittings Beam Beam and block Column Composite solid slab Foundation unit Frame unit Hollow core Precast concrete pile unit Staircase unit

Technical specification BS EN 1340:2003 BS EN 1917:2002 BS EN 1916:2002 BS EN 13224:2004 BS EN 1338:2003 BS EN 1340:2003 BS EN 1339:2003 BS EN 1340: 2003 BS EN 771-4:2003 BS EN 771-3:2003 BS EN 771-3:2003 BS 1217:1997 BS 5642-2:1983 BS EN 1340:2003 BS EN 845-2:2003 BS EN 771-5:2003 BS 5642-1:1978 BS EN 13225:2004 BS EN 206-1:2000 BS EN 13225:2004 BS EN 206-1:2000 BS EN 13225:2004 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 13747:2005 BS EN 1168:2005 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 1338:2003 BS EN 1340:2003 BS EN 1340:2003 BS EN 1340:2003 BS EN 13747:2005 BS EN 490:2004 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 13225:2004 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 13225:2004 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000 BS EN 206-1:2000

Table 21: Manufactured concrete products and relevant technical specifications

79

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