Leaching L0333 AGG079 003 BRE

8/10/2019 Leaching L0333 AGG079 003 BRE

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Aggregates programme/Final report

Testing of concrete to determine

the effects on groundwater

The objective of this project was to assess the suitability of common testmethods for determining the leaching characteristics of recycled,secondary and primary aggregates, concrete containing theseaggregates, and the criteria against which to assess the test results.

Project code:AGG079003 ISBN:1-84405-316-4

Research date:July 2005 to March 2007 Date:September 2007


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Front cover photograph:Concrete produced with recycled aggregates

WRAP and BRE believe the content of this report to be correct as at the date of writing. While steps have been taken to ensure accuracy, WRAP

cannot accept responsibility or be held liable to any person for any loss or damage arising out of or in connection with this information being

inaccurate, incomplete or misleading. For more detail, please refer to WRAPs Terms & Conditions on its web site: www.wrap.org.uk

Published by

Waste & Resources The Old Academy Tel: 01295 819 900 Helpline freephone

Action Programme 21 Horse Fair Fax: 01295 819 911 0808 100 2040

Banbury, Oxon E-mail: [email protected]

OX16 0AH


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Testing of concrete to determine the effects on groundwater 1

Executive summary

Recycled and secondary aggregates have a key role within a sustainable construction industry. With the desire for

improved environmental performance and sustainability, there is an increasing interest in the potential use of

recycled and secondary materials as aggregates in concrete. However, there is little available information

regarding the potential for hazardous species to be leached from concrete and aggregates into controlled waters

(groundwater and drinking water).

The objective of this project was to utilise a range of test methods that are currently available to assess leaching

from concrete made with recycled and secondary aggregate sources and compare the results with those from

primary aggregates. The results of the tests have been compared against leaching acceptance criteria.

The results indicated that the primary aggregates generally performed similarly to recycled and secondary

aggregates tested. The concentrations of some species, particularly sulfates and total dissolved solids, appeared

high in some of the leachates from concretes, but this was generally attributable to the Portland cement present

in the concrete mixes tested, rather than to the aggregates themselves.

Overall, the project results imply that the suitability of aggregates for their place of use (in terms of the release of

undesirable substances) could be determined by:

Testing the aggregates in accordance with BS EN 1744-3:2002 the leachate test for aggregates1

Comparing the results with the inert waste acceptance criteria for inert waste (based on the understanding

that inert wastes are suitable for recycling)2.

Abbreviations for resources used for producing aggregates used in project

BR Crushed brick

CC Crushed concrete

CL Cheddar limestone

RS Spent railway sleeper

FS Foundry sand

IBAA Incinerator bottom ash aggregate

PC Portland cement

PDL Peak District limestoneRAP Recycled asphalt planings

TV Thames Valley aggregate

1See reference 4

2See reference 10


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Contents

1.0 Introduction............................................................................................................................. 3

2.0 Testmethods............................................................................................................................ 4

2.1 Leaching test methodology............................................................................................... 5

2.2 BS EN 12457-2:2002 ......................................................................................................... 5

2.3

BS EN 1744-3:2002 ........................................................................................................... 5

2.4 EA NEN 7375:2004 ............................................................................................................ 6

2.5 Chemical analysis of leachate........................................................................................... 6

2.6 Assessment criteria for leaching test results................................................................... 7

2.7 Assessment of turbidity and colour .................................................................................. 8

3.0 Specimen preparation.............................................................................................................. 9

3.1 Concrete mixes and aggregates used .............................................................................. 9

3.2 Specimen manufacturing and testing ............................................................................ 10

3.3 Mix designs ...................................................................................................................... 10

3.4 Specimen preparation including curing ......................................................................... 10

3.5 Properties of fresh and hardened concrete ................................................................... 11

4.0 Results ................................................................................................................................... 13

4.1 Leaching from aggregates .............................................................................................. 13

4.1.1

Aggregates tested in accordance with BS EN 12457-2:2002.......................................13

4.1.2 Aggregates tested in accordance with BS EN 1744-3:2002 ........................................14

4.1.3 Discussion of results................................................................................................16

4.2 Leaching from granular concrete specimens................................................................. 18

4.2.1 Granular concrete specimens tested in accordance with BS EN 12457-2:2002.............18


4.3 Leaching from monolithic concrete specimens ............................................................. 23

4.3.1 Monolithic concrete specimens tested in accordance with EA NEN 7375:2004.............23


4.4 Turbidity and colour testing............................................................................................ 27

4.5 Overall view: leaching performance of aggregates....................................................... 27

4.6 Overall view: leaching performance of concrete at 28 days and 1 year ......................27

5.0

Conclusions ............................................................................................................................ 285.1 Leaching performance of materials................................................................................ 28

5.2 Suitability of test methods.............................................................................................. 29

6.0 Suggestions for further work................................................................................................. 29

Annex A - Leaching assessment criteria ............................................................................................ 32

Annex B - Comparison of results between laboratories using BS EN 1744-3:2002........................... 34


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1.0 IntroductionThe need for a more sustainable construction industry, as well as increasing pressures on landfill space, have led

to an increasing use of recycled and secondary materials as aggregates in concrete1,2. However, if users are to

have full confidence in these materials, it is important that they are shown to have neither an adverse impact on

the properties of concrete, nor on the environment, through leaching of hazardous materials. However, only

limited data regarding the potential for leaching from concrete containing such materials into controlled water

(groundwater and drinking water) are currently available.

It is widely accepted that the leaching behaviour of potential recycled and secondary aggregate materials needs

to be assessed. However, a universally accepted method to assess this is not yet established. Several test

methods to assess leaching behaviour for different situations are available. However, very different leaching

conditions are adopted in each and the choice of a test methodology to represent the in-service leaching

characteristics of the material is not straightforward. Some methods may appear too severe, while others may

seem too conservative. There is concern that the results from a severe test, together with the use of acceptance

criteria that are too restrictive, may be unrealistic and could preclude the use of suitable materials. On the other

hand, if the criteria or the test method are too lenient, there is a risk that potentially dangerous substances could

find their way into the environment. It is therefore not surprising that standard methods and assessment criteria

have not yet been agreed among stakeholders to assess the leaching performance of aggregates in concrete.

The objective of the project was to assess the leaching characteristics of concrete containing recycled and

secondary aggregates using several of the standard tests already practiced in the UK or specifically proposed for

aggregate materials3, 4,5. These results are compared with results for primary aggregates. Results produced by

different laboratories testing the same materials have also been assessed.

This report summarises the results of leaching tests on a range of recycled and secondary aggregates used in

concrete. Otherwise equivalent concretes made using primary aggregates have been included to provide a basis

for comparison. The results were compared with a series of leaching acceptance criteria developed for various

purposes, including waste acceptance.

It must be stressed that the leaching from different sources of the same type of material could vary considerably,

and any specific material should be considered on a case-by-case basis, rather than solely relying on the resultsobtained during this study. Further information on the leaching characteristics of generic material types is given

on the AggRegain website6.

This work was carried out for WRAP by the Building Research Establishment (BRE) and Scott Wilson (SW).


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2.0 Test methodsStandard methods for assessing the leaching behaviour of aggregates in concrete (particularly concrete in contact

with drinking water), are currently under development. Hence, the approach taken within this project was to use

a range of tests developed for assessing aggregates, building materials and wastes for landfill. These tests were

applied to recycled, secondary and primary aggregates, as well as to concrete specimens made from these

aggregates. The concrete mixes had been proposed and agreed by an Industry Consultative Group to reflect

evolving testing standards. Relevant results from the tests have been presented in this report and in a database.

Three different leaching test methods were utilised to assess the performance of recycled, secondary and primary

aggregates as unbound aggregates, as crushed concrete, and as monolithic concrete specimens.

BS EN 12457-2:2002Characterisation of waste Leaching Compliance test for leaching of granular

waste materials and sludges. Part 2 A rapid tumble-style test carried out on granular/ crushed material,

with a history of use in the UK and understood by the Environment Agency (EA), the Scottish Environment

Protection Agency (SEPA) and other regulators.

BS EN 1744-3:2002Tests for chemical properties of aggregates Part 3: Preparation of eluates by

leaching of aggregates A rapid stirred tank test carried out on crushed aggregate material and based on the

assumption that equilibrium or near-equilibrium is achieved between the liquid and solid phases during the

test period. This test has a limited history of use in the UK but has been specifically developed to characterise

aggregates rather than waste materials.

EA NEN 7375:2004Leaching characteristics of moulded or monolithic building and waste materials This

test has been recently introduced to the UK to assess monolithic waste materials. The test is based on a

standard from the Netherlands for assessing leaching from monolithic construction materials such as concrete.

This is a non-aggressive tank test with no stirring required over a duration of 64 days.

The concentrations of chemical species in the leachate were determined following the completion of each

leaching stage of these tests. In addition, on completion of the EA NEN testing, the turbidity and colour of a

selection of water samples were assessed.

A further standard method, (Influence of cementitious products on water intended for human consumption - Test

methods - Part 3, BS EN 14944-1: 2006) was considered for inclusion in this work. The standard describes test

procedures to generate solutions from concrete products such as pipes. However, criteria for evaluation of the

leachates are still being developed. As a result (and with the agreement of the Industry Consultative Group), the

method was rejected for use in this project.

The Industry Consultative Group consisted of Dr Mike Taylor from the British Cement Association (BCA) and

Professor Tom Harrison from the Quarry Product Association (QPA). Both Dr Taylor and Professor Harrison have

wide experience in the concrete and cement industries, particularly in European standardisation, including

leaching test methods. They are also both involved in the European Standardisation Committee related to

concrete, aggregates and the water environment.


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2.1 Leaching test methodology

Figure 1 shows a schematic diagram of the testing methodology adopted during the project (further details of the

individual test methods are given in subsequent sections of this report).

Figure 1: Schematic diagram of the approach to concrete production and leaching tests

2.2

BS EN 12457-2:2002

This method was used to test the primary, recycled and secondary aggregates in their unbound state and also inconcrete specimens aged for 28 days and 1 year respectively that had been crushed before testing. The standard

requires that specimens are crushed in a jaw crusher so that at least 95% by mass of the material had a grain

size of less than 4 mm. The material was then exposed to water leachant, at a liquid-to-solid ratio of 10 l/kg, and

tumbled for 24 hours. The leachate is then collected, filtered and analysed for the agreed determinands (see

Section 2.5).

The suitability of this test was questioned by the Industry Consultative Group. It requires crushing of the

aggregate and concrete specimens and could be regarded as too severe to reflect the behaviour of aggregates or

the concrete in service. However, the test is expected to provide an indication of the worse case scenario for

leaching and it was therefore considered to be of value to the project. The test also has a significant history of

use in the UK and may be more familiar to regulators. This test is specified for Waste Acceptance testing7,8,9,

which can be used to determine whether material is inert, and by implication, suitable for recycling10.

2.3

BS EN 1744-3:2002

This method was used to test the primary, recycled and secondary aggregates in their unbound state without

further crushing. Crushed concrete containing these aggregates was not assessed using this method since it is

specifically designed to test aggregates and not other building products. BS EN 1744-3: 2002 is a tank test,

where an aggregate test portion is immersed in a large volume of leachant. The test portion is placed on a screen

insert and leached in a tank for 24 hours, at a liquid-to-solid ratio of 10:1 l/kg. The water is agitated by a motor-

driven dip stirrer. The method is based on the assumption that equilibrium or near-equilibrium is achieved

between the liquid and solid phases during the test period. The leachate is then collected, filtered and analysed

for the agreed determinands (see Section 2.5).

Crush

BS EN 12457-2 BS EN 12457-2

(tested at 28 days

& 1 year)

Crush at 28 days or 1 year

Compressive

strength test

EA NEN 7375

(tested at 28 days

& 1 year)

BS EN 1744-3

Prepare concrete

cubes

Store

Prepare concrete

cylinders

Store for 28

days & 1 year

Aggregate


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This method is more representative of the aggregate in service than BS EN 12457-2:20023, as the test portion

has a similar particle size to that of the aggregate in use. However, this test is reasonably new to the UK, with

little history of use, and may be unfamiliar to regulators.

2.4 EA NEN 7375:2004

This method was used to test concrete specimens made with primary, recycled and secondary aggregates aged

under sealed conditions in the laboratory to test ages 28 days and 1 year. EA NEN 7375 is a tank diffusion test inwhich monolithic materials, (in this case, concrete cylinders), are placed in contact with water leachant for 64

days without agitation. The leachant is regularly refreshed during the test period and the leachate analysed to

provide an indication of leaching characteristics with time. Results are expressed in terms of cumulative leaching

in mg/m2. The standard indicates that the leachant should be refreshed nine times during the 64 days. However,

on the advice of the Industry Consultative Group, the project team agreed that only five leachate specimens

needed to be collected and analysed for the agreed determinands (see Section 2.5).

This method is more representative of the concrete in service than BS EN 12457-2:2002 which requires the

concrete to be crushed. Despite this benefit, the time required to undertake the testing is likely to make it

unsuitable for compliance testing. The test is also reasonably new to the UK, with little history of use and may be

unfamiliar to regulators. However, this test is specified for waste acceptance testing and it can be used to

determine the leaching characteristics of monolithic materials.

There were minor differences between the approaches adopted in the different laboratories. A comparison to the

standard test method given in EA NEN 7375:2004, is shown in Table 1.

Table 1 : Comparison of Standard test method and methods used by BRE and SW

Variable EA NEN 7375:2004 method BRE laboratory SW laboratory

Specimen size Dimensional limits are definedCylinder: 0.08 m2

surface area

Cylinder: 0.11 m2

surface area

Volume of container

Sealable plastic tanks without softening

agents of volume between 2 and 5 times

the volume of the test specimen, and ofdimensions such that the specimen is

surrounded by at least 2 cm of water on all

sides

13.2 litre Low

density

polyethylene(LDPE) buckets

with handle and

air-tight lid

33 litre food

quality

polypropylenebuckets with air

tight lids and

taps

Leachant replenishment

interval

1 hr, 6 hr and , 1, 2.25, 4, 9, 16, 36, 64

days1, 2.25, 4, 16, 64 days.

Leachant volume per

specimen for each

replenishment

50 and 200 times the surface area (in m2)

of the test piece7.5 litres 14.14 litres

Specimen support method Not specifiedPlaced on section

of downpipe

Suspended in

nylon netting

Expression of results Diffusion or dissolution Cumulative leaching (dissolution)

2.5

Chemical analysis of leachate

Analysis of the leachates was sub-contracted to two different UKAS accredited testing laboratories. Instrumental

methods of chemical analysis were employed and the results were interpreted by BRE and SW. There were

differences in the detection limits for some determinands between the laboratories and there were also temporal

variations in detection limits for individual determinands, (probably due to variations in the calibration of

equipment at the time of the analysis). Some of the detection limits exceeded the threshold criteria against

which the results were assessed and this restricted the interpretation of the results.

The determinands used to characterise the leaching from the aggregate and concrete specimens are shown in

Table 2. The determinands were chosen following a review of the elements on List I and List II in the EC

Dangerous Substances Directive11, the elements listed as Waste Acceptance Criteria in the Landfill (England and

Wales) Regulations 2002 (as amended)7,8,9and the elements commonly found in cement. The metallic

determinands used to assess the appropriate landfill disposal route are present in List I and II of the EC


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Dangerous Substances Directive (76/464/EEC), with the exceptions of vanadium, iron and boron which are not

used for waste acceptance testing. Since sodium and potassium salts (which are constituents of Portland

cements) are highly soluble and are known to cause environmental damage, these determinands were added to

the leachate testing suite. There was little expectation that significant quantities of organic material would be

contained within the recycled, secondary and primary aggregates or their leachates.

Table 2: Determinands used to analyse leachate

Determinands Notes

Arsenic (As) Lead (Pb)

Cadmium (Cd) Mercury (Hg)

Total Chromium (Cr) Nickel (Ni)

Copper (Cu) Zinc (Zn)

BTEX compounds (benzene, toluene, ethyl benzene & xylenes)

pH

Included in List I or List II of the

Dangerous Substances Directive11and

as waste acceptance criteria in the

Landfill Regulations7,8,9

Barium (Ba) Molybdenum (Mo)

Chloride (Cl) Antimony (Sb)

Fluoride (F) Selenium (Se)

Sulphate (SO4)

Phenol Index (PI) Total Dissolved Solids (TDS)Polyaromatic Hydrocarbons (PAH) Mineral Oil (C10 C40)

Dissolved Organic Carbon (DOC) Total Organic Carbon (TOC)

Polychlorinated Biphenyls (PCBs) (7 congeners)

Included as waste acceptance criteria in

the Landfill Regulations7,8,9

Vanadium (V) Iron (Fe) Boron (B)Included in the List I or List II of the

Dangerous Substances Directive11

Sodium (Na) Potassium (K) Derived from cement composition

2.6 Assessment criteria for leaching test results

The leaching test results were compared with thresholds for the acceptance of wastes into landfill7,8,9, In this

report, these thresholds are sometimes referred to as Waste Acceptance Criteria (WAC), and are detailed inAnnex A. The BS EN 12457-2:2002 test is specifically intended to assess wastes against these criteria and tests

are conducted on fine graded, irregular granular materials, with the level of leaching expressed in mg/kg. The

leaching test results for the unbound aggregates in accordance with BS EN 1744-3:2002 were also assessed

against these criteria. There are also thresholds (referred to as Monolith Criteria in this report), for the

acceptance of monolithic wastes into landfill that have been tested in accordance with EA NEN 7375:2004. The

leaching test results are expressed in mg/m2, to reflect the surface area of the monolith over which leaching has

occurred.

Although the WAC for granular and monolithic wastes are intended for the disposal of wastes to landfill, they

provide a reference point for aggregates, as uncontaminated construction, demolition and excavation wastes

used to produce recycled aggregate and recycled concrete aggregates are considered to be inert10. Leaching

results from both BS EN 12457-2: 2002 and BS EN 1744-3: 2002 are most appropriately reported as mg/kg to

permit comparison to the WAC.

Drinking Water Standards (WQS)12and Environmental Quality Standards (EQS)13are thresholds for List I and List

II substances that are intended to assess the quality of drinking water and water in surface water bodies (such as

lakes and streams). In addition, assessment of determinand content in soil waters against the EQS forms the

basis of the Environment Agencys assessment of risk from contaminated land13. Comparison of leaching test

results to these thresholds requires reporting of determinands as g/l (of leachate). If the levels of leaching from

recycled and secondary aggregates (or concrete containing these aggregates), are less than the thresholds given

in WQS or EQS, it should be readily accepted that they pose no risk to drink water or to controlled waters. Details

are given in the database associated with this project.

All the aggregate materials assessed under this project failed to meet the requirements of both the WQS and EQS

and the comparisons are not included in this report. The WQS and EQS thresholds are relevant for assessing thesuitability of aggregates or concretes for use in sensitive areas, such as river revetments. However, in water


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environments, the dilution of leached substances by the water body (for example, the reservoir or river), with the

application of suitable source-pathway-receptor models, must be considered as part of an assessment.

Results from this study have been accumulated in a database in which leaching values are expressed in the

preferable units mentioned above for each test, as well as in g/l.

2.7 Assessment of turbidity and colour

Organoleptic drinking water tests (such as colour, turbidity, odour and taste) were considered for inclusion in thisproject. These are not strictly applicable to concrete although they are applicable to drinking water which is

stored in concrete towers and reservoirs. Since the tests are based on assessments of the taste and odour of

drinking water by specialist tasters, neither of the two drinking water testing laboratories approached were willing

to assess water that had been in contact with experimental concrete and aggregates in this way. As a result, a

revised approach, using turbidity and colour assessment was agreed with the Industry Consultative Group. The

available standards relevant to turbidity and colour at present are:

BS 6920-2: 2000

Suitability of non-metallic products, quality of water gives methods for assessing the turbidity (suspended -

material) and colour of the water. Methods for assessing taste and odour are also given. Samples of the solutions

obtained at 24 hours by BRE from concrete monoliths using the EA NEN 7375: 2004 were sent for laboratory

assessment for turbidity and colour/appearance using the BS 6920-2 methods. Assessment was made by thesame laboratory that carried out the leachate analysis for BRE.

The colour of water, which is generally due to dissolved organics or iron compounds, can be measured using

photometers or colorimeters. These shine a fixed wavelength light through the specimen and measure the

amount of light that has been absorbed. The prescribed concentration or value (PCV) from the WQS is 20

mg/litre measured colorimetrically using a Pt/Co light source.

Turbidity in liquidsis caused by the presence of un-dissolved but finely dispersed matter. The unit of measure

adopted by water authorities, the NTU (Nephelometric Turbidity Unit)14. For drinking water, at the customers tap

(from the WQS), the PCV is 4.0 NTU. Results for the turbidity and colour of specimens are given in Section 4.4.


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3.0 Specimen preparation3.1

Concrete mixes and aggregates used

Four control concrete mixes (made with primary aggregates), were produced. For the test mixes, the recycled

and secondary aggregates were used to replace either all of the 10/20 and 4/10 mm fraction of primary

aggregates in the control concrete mix (Control 1) or, in the case of the foundry sand, blended to form the

optimum amount of the finest fraction of the 0/4 mm primary sand. Table 3 provides details of the aggregates

used and how they were incorporated into the project concrete mixes.

Table 3: Summary of concrete mix names, and the test aggregate in each

Primary aggregates used in control mixes

Concrete mix Aggregate Comments (reason for choice)

Control 1 Thames Valley riversand/gravel (TV)

Control mix containing a common concrete aggregate.

Control 2 Crushed Cheddar limestone

(CL)

Control 3 Crushed Cheddar limestone

(CL)

The same CL aggregate was tested in control mixes

produced by both the BRE Laboratory (Control 2) and

the SW laboratory (Control 3) in order to establish the

equivalence of the concrete manufacturing processes

and the robustness of the leaching test methodologies.

Control 4 Crushed Peak District

limestone rock (PDL) with

10% asphalt planings (RAP)

Control for the RA1 concrete specimen, so any

leaching experienced can be attributed to the

appropriate component (that is, the recycled concrete

or the asphalt).

Recycled and secondary aggregates used in test mixes

Concrete mix name Aggregate Comments (reason for choice)

Recycled concrete

aggregate (RCA)Spent railway sleeper (RS)

Crushed concrete with a possibility of low level of

contamination with lubrication oil/ fuel.

Recycled aggregate

(RA1)

Crushed concrete with 10%

asphalt planings (CC/RAP)

BS 8500-2:2006 restricts the levels of asphalt in

recycled concrete aggregate to 5%15and to 10% in

recycled aggregate. In this instance, 10% RAP was

included to determine the potential of leaching of

organic components from the bitumen in the asphalt.

Recycled aggregate

(RA2)

Crushed concrete (CC) with

crushed brick (BR)

BS 8500-2:2006 allows recycled aggregate to be made

up of 100% masonry15.

Secondary aggregate

(SA1)Foundry sand (FS)

Foundry sand is not a widely available aggregate16,

but it is potentially contaminated with organic

compounds which could leach out of the concrete.

They are typically fine sized sands.

Secondary aggregate

(SA2)

Incinerator bottom ash

aggregate (IBAA)

IBAA is increasingly available17and has good potential

as an aggregate in concrete.


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3.2 Specimen manufacturing and testing

In order to assess the robustness of the leaching test procedures, BRE and SW laboratories prepared and tested

aggregates and concrete specimens, as summarised in Table 4.

Table 4: Summary of specimen manufacture and testing

Testing laboratory

Leachate preparation method

BS EN 12457-2:2002 BS 1744-3:2002

Aggregate

Leachate

preparation

Leachate

analysis

Leachate

preparation

Leachate

analysis

Thames Valley river sand: 0/4 mm (TV) SW SW SW SW

Thames Valley river gravel: 4/20 mm (TV) BRE BRE BRE SW

Crushed Cheddar limestone rock 10/20 mm (CL) SW SW SW SW & BRE

Crushed Cheddar limestone rock 4/10 mm (CL) SW SW SW SW

Crushed Cheddar limestone rock 4/20 mm (CL) BRE BRE - -

Crushed Peak District limestone rock 4/20 mm (PDL) SW SW SW SW

Spent railway sleeper 4/20 mm (RS) BRE BRE SW SW

Crushed concrete 4/20 mm (CC) SW SW SW SW

Recycled asphalt planings 4/20 mm (RAP) SW SW SW SW

Crushed concrete with crushed brick 4/20 mm (CC/BR) BRE BRE BRE SW

Foundry sand (FS) BRE BRE - -

Incinerator bottom ash aggregate 4/20 mm (IBAA) SW SW SW SW & BRE

Concrete mix

Concrete specimen

manufacture

Leachate preparation

and analysis

Control 1 BRE BRE

Control 2 BRE & SW BRE & SW

Control 3 SW SW

Control 4 SW SW

RCA BRE BRE

RA1 SW SWRA2 BRE BRE

SA1 BRE BRE

SA2 SW SW

3.3 Mix designs

Mix designs were based on a fixed cement content of 280 kg/m3, and a free water/cement ratio of approximately

0.6. The mix design is based on the minimum cement content required for a concrete to be placed in contact with

groundwater, soil or surface water17.

With the exception of the mix containing foundry sand as a partial sand replacement, the fine fraction (0/4 mm)

used was entirely Thames Valley (TV) sand, and the coarse fraction of aggregates (4/20 mm) was the particular

primary, recycled or secondary aggregate being studied. A summary of the particle size range and types of

aggregates used in each concrete mix are given in Tables 5a and b. The maximum proportion of the FS (25% by

weight of the sand fraction) in the SA1 concrete mix was controlled by its particle size within the overall sand

grading. More detailed mix designs together with fresh and hardened concrete properties are given in Section

3.5.

3.4 Specimen preparation including curing

The concrete specimens included 100 mm cubes for compressive strength testing and crushing for the BS EN

12457-2: 2002 test, and cylinders for the EA NEN 7375:2004 test, as described in Tables 6a and 6b.


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Table 5a: Aggregate type and grading for BRE manufactured concrete specimens

Concrete mix name Control 1 Control 2 RCA RA2 SA1

Cement type PC PC PC PC PC

10/20 mm TV CL RS CC/BR TV4/10 mm TV CL RS CC/BR TV

0/4 mm TV TV TV TV FS/TV

Table 5b: Aggregate type and grading for SW manufactured concrete specimens

Concrete mix name Control 3 Control 4 RA1 SA2

Cement type PC PC PC PC

10/20 mm CL PDL/RAP CC/RAP IBAA

4/10 mm CL PDL/RAP CC/RAP IBAA

0/4 mm TV TV TV TV

Table 6a: Concrete specimens cast at BRE

Specimens Curing (20C) Testing

11 cubes (100 mm) Under damp sacking and polythene for 3

days (with demoulding at 24 hrs)

Seal in plastic at 3 days and store

Compressive strength at 28 days

(3 cubes)

Store in sealed condition for leaching

tests (8 cubes) at 28 days and 1 year

2 cylinders (200 mm x100 mm diameter)

Under damp sacking and polythene to 3days age (with demoulding at 24 hrs)

Seal in plastic at 3 days and store Store in sealed condition for leaching

tests (2 cylinders) at 28 days and 1 year

Table 6b: Concrete specimens cast at SW

Specimens Curing (20C) Testing

8 cubes (100 mm) Under damp sacking and polythene to 3

days age (with demoulding at 24 hrs)


Compressive strength at 28 days

(3 cubes)


tests (5 cubes) at 28 days and 1 year

6 cylinders (160 mm x

150 mm diam)

Under damp sacking and polythene to 3

days age (with demoulding at 24 hrs)



tests (3 cylinders) at 28 days and 1 year

3.5 Properties of fresh and hardened concrete

The properties of the fresh and hardened concrete, where measured, are given in Table 7a and b. The mean 28

day compressive strength of the Cheddar limestone control mixtures (Control 2 and Control 3) are similar for both

the BRE & SW laboratories (42.5 and 41.5 N/mm2respectively), which is indicative of consistent manufacturing

processes between the two laboratories.


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As the mixes were intended for leaching assessments, they were designed with equal cement contents and were

not adjusted to achieve a specific compressive strength. Therefore, it should not be concluded that the lower 28

day compressive strength compared to the control indicate that crushed brick or IBAA are unsuitable as

concreting aggregates.

Table 7a: Mix proportions and properties of concrete specimens manufactured at BRE

% of total aggregate

(nominal size) Fresh and hardened concrete properties

Aggregate

heoretical

PC content

in kg/m3

[actual]

Free

Water

(kg/m3)

Free

w/c 0/4

mm

4/10

mm

10/20

mm

Wet

density

(kg/m3)

Slump

(mm)

Mean

cube

density

(kg/m3)+

Mean 28 day

compressive

strength

(N/mm2)+

Control 1 280 [280] 168 0.60 40 20 40 2330 90 2343 35.0

Control 2 280 [280] 168 0.60 40 20 40 2410 50 2423 42.5

RCA 280 [282] 168 0.60 40 60 2300 80 2330 35.5

RA2 280 [280] 168 0.60 40 60 2200 80 2220 26.5

SA1 280 [279] 168 0.60 40* 20 40 2370 90 2373 35.5

[ ] Actual Portland Cement (PC) (kg/m3).

* Foundry sand at 25% of 0/4 mm content (remainder was primary sand).+ Mean 28 day compressive strength and cube density determined from the results of 3 specimens.

Table 7b: Mix proportions and properties of concrete specimens manufactured at SW

% of total aggregate

(nominal size)Fresh and hardened concrete properties

Aggregate

heoretical

PC content

in kg/m3*

Free

Water

(kg/m3)

Free

w/c 0/4

mm

4/20

mm

10/20

mm

Wet

density

(kg/m3)

Slump

(mm)

Mean

cube

density

(kg/m3)+

Mean 28 day

compressive

strength

(N/mm2)+

Control 3 280 168 0.60 40 20 40 n/d n/d 2425 41.5Control 4 280 168 0.60 40 60 n/d n/d 2384 30.5

RA1 280 168 0.60 40 60 n/d n/d 2258 29.0

SA2 280 168 0.60 40 60 n/d n/d 2167 22.5* Actual cement content not determined.+ Mean 28 day compressive strength and cube density determined from the results of 3 specimens.

n/d Not determined.


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4.0 Results4.1 Leaching from aggregates

4.1.1 Aggregates tested in accordance with BS EN 12457-2:2002Table 8 and Table 9 show the results for crushed samples of the unbound aggregates used in the concrete mixes,

compared to the Waste Acceptance Criteria7,8,9. Table 8 gives the results for the primary aggregates and Table 9,

for the recycled and secondary aggregates. The results are expressed as mg/kg of dry substance. Shaded cells in

the data indicate where results exceed the threshold WAC. The WAC have three levels for:

Inert Waste, shown in yellow, below which wastes are considered to be inert and by implication, suitable for

recycling10.

Stable Non-Reactive Hazardous Waste (SNRHW), shown in orange, below which wastes are suitable to bedisposed of in the same landfill cell as non-hazardous waste.

Hazardous Waste, shown in pink, below which wastes can be disposed in hazardous waste landfill, abovewhich, waste must be treated before disposal.

Table 8: Leaching from primary aggregates tested in accordance with BS EN 12457-2:2002

SampleThames Valleyriver sand and

gravel (TV)

Crushed Cheddar limestonerock (CL)

CrushedPeak District

limestonerock (PDL)

Aggregatefraction

4/20mm

0/4mm

4/20mm

10/20mm

4/10mm

4/20mm

Inertwaste

SNRHWHazardous

waste

Arsenic


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^PAH - polyaromatic hydrocarbonsxTPH - total petroleum hydrocarbons

Table 9: Leaching from recycled and secondary aggregates tested in accordance with BS EN 12457-

2:2002

Sample

Spentrailway

sleeper(RS)

Crushedconcrete

(CC)

Recycledasphalt

planings(RAP)

Crushedconcrete

with

crushedbrick

(CC/BR)

Foundrysand(FS)

Incineratorbottom ash

aggregate(IBAA)

Aggregatefraction

4/20mm

4/20mm

4/20mm

4/20mm

0/4mm

4/20mm

Inertwaste

SNRHW Hazardouswaste

Arsenic


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SampleThames Valleyriver sand and

gravel (TV)

Crushed Cheddar limestonerock (CL)

CrushedPeak District

limestonerock (PDL)

Aggregatefraction

4/20mm

0/4mm

10/20mm

10/20mm

4/10mm

4/20mm

Inertwaste

SNRHWHazardous

waste

Leaching stepconducted by:

BREAssoc.

SWBRE

Assoc.SW SW SW

Analysis stepconducted by:

BREAssoc.

SWAssoc.

BREAssoc.

SWAssoc.

SWAssoc.

SWAssoc.

Arsenic


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Specimen

Spentrailwaysleeper

(RS)

Crushedconcrete

(CC)

Recycledasphaltplanings

(RAP)

Crushedconcrete

withcrushed

brick

(CC/BR)

Foundrysand(FS)

Incineratorbottom ashaggregate

(IBAA)

Aggregatefraction

4/20mm

4/20mm

4/20mm

4/20mm

0/4mm

4/20mm

Inertwaste

SNRHWHazardous

waste

Leaching stepconducted by

BREAssoc.

SW SW BRE AssocBRE

AssocSW

Analysis stepconducted by

BREAssoc.

SWAssoc.

SWAssoc.

BREAssoc.

BREAssoc.

SWAssoc.

Arsenic


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The Thames Valley sand (0/4 mm) slightly exceeded the Inert WAC for fluoride, but the amount of fluoride

did not exceed that required for the Stable Non-Reactive Hazardous Waste (SNRHW) category, (Table 8). Theimplication is that, if it were a waste, the material would be classified as non-hazardous and by implication,would not automatically be suitable for use as recycled aggregate (that is, it would fail to meet the criteria set

out in the quality protocol for aggregates10). In this instance, the threshold criterion for fluoride was onlyexceeded by 1 mg/kg on one aggregate test portion. This result might not be repeated over a range of

samples.

The Peak District limestone exceeded the Inert WAC for chromium, chloride and total dissolved solids, but notthe criteria for the WAC SNRHW category, (Table 8). Hence, if it were a waste, the material would be

classified as non-hazardous. The Peak District limestone was the only aggregate to leach significant levels ofchromium. This is possibly associated with mineralisation of the Peak District limestone.

The crushed concrete (CC) exceeded the Inert WAC for copper, molybdenum, lead, antimony, sulfate andtotal dissolved solids, but not the criteria for the WAC SNRHW category, (Table 9). Hence, if it were a waste,the material would be classified as non-hazardous. However, the results of the leaching from the same source

of crushed concrete combined with crushed brick (CC/BR) did not exceed these thresholds. The following arepossible explanations for this:

The addition of crushed brick to the crushed concrete dilutes the aggregate sufficiently that leachingno longer exceeds the WAC thresholds (this dilution effect might also be related to the reducedsurface area of the crushed concrete fraction available for leaching).

The concrete has a sufficiently variable composition to produce different results in leaching test trials.

There is a difference in the testing methodologies employed by the two laboratories which results in a

different result for the crushed concrete and the crushed concrete with crushed brick.

The results for the Cheddar limestone indicate that the testing is consistent between the two laboratories and

this explanation can therefore be discounted. The implication is that either the crushed concrete source isvariable, or that the aggregate is diluted by the addition of crushed brick. As the concrete is sourced from a

source of low variability (processed, redundant pre-cast railway sleepers), the most likely cause is effectsassociated with the dilution of the crushed concrete with crushed brick.

The foundry sand (FS) exceeded the WAC inert waste limits for nickel but not the SNRHW category. Hence, if

it were a waste, the material would be classified as non-hazardous and by implication.

The spent railway sleepers (RS) exceeded the WAC inert limit for total dissolved solids but not the SNRHW

category. Hence, if it were a waste, the material would be classified as non-hazardous.

It is clear from these results that the recycled, secondary and primary aggregates examined in this study undergo

measurable leaching when tested in accordance with BS EN 12457-2:2002, and several exceed the WAC for inert

waste. Commonly used concreting primary aggregates, such as Thames Valley sand and gravel and Cheddar

limestone crushed rock, do not leach significantly. However Peak District limestone (a commonly used primary

aggregate), failed to meet several of the WAC thresholds for inert waste. The findings imply that leaching tests in

accordance with BS EN 12457-2:2002 and applying pass/fail criteria to aggregate by assessing the results

against current WAC for inert waste, is not a suitable means for assessing fitness for purpose.

If they were considered as a waste, the recycled and secondary aggregates discussed above would be classified

as non-hazardous (rather than inert) and by implication, would not automatically be considered suitable for use

as recycled aggregate. Nevertheless, it is possible that the materials could be demonstrated suitable for use

following agreement with appropriate regulators and following further testing if appropriate.

The leaching from aggregates tested in accordance with BS EN 1744-3:2002 (Table 10 and Table 11), which uses

conditions that are less severe than the BS EN 12457-2:2002 test, shows that: None of primary aggregates exceed the Inert WAC.

Only the foundry sand (FS) and the incinerator bottom ash aggregate (IBAA) exceed the Inert WAC.

The leachate from FS exceeds the Inert WAC threshold for nickel. There were no significant differences fromthe results obtained using BS EN 12457-2:2002.

The IBAA specimen exceeds the Inert WAC thresholds for antimony, chloride, sulfate and total dissolvedsolids.

The results for FS are unsurprising since, as it is a fine aggregate (


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this case, since analysis of eluate from IBAA without particle size reduction in two different laboratories gave

similar results.

In general, these results imply that testing aggregates in accordance with BS EN 1744-3:2002, and then

comparing the results to the WAC might be a convenient means to determine if an aggregate is suitable for use.

This conclusion is based on the evidence that this standard test and comparison does not reject primary

aggregates which are already accepted for use without testing, and have no history of deleterious environmental

impact.

4.2 Leaching from granular concrete specimens

Concrete specimens containing primary aggregates and recycled or secondary aggregates, were crushed and

tested in accordance with BS EN 12457-2:2002 after 28 days and 1 year. These specimens are referred to as

granular concrete specimens to avoid confusion with the crushed concrete (CC) used as a recycled aggregate in

the experimental programme. All data are presented in units of mg/kg of dry substance.

4.2.1 Granular concrete specimens tested in accordance with BS EN 12457-2:2002Table 12 to Table 16 show the leaching results from granular concrete specimens (concrete crushed to comply

with the test procedure) tested at 28 days and 1 year. The coloured shading indicates where results exceed the

corresponding WAC thresholds for particular determinands.

Table 12: Leaching results from granular concrete TVS and PDL control specimens at 28 days and 1

year tested in accordance with BS EN 12457-2:2002

Specimen and ageControl 1

TVS28 days

Control 1TVS

1 year

Control 4PDL+ 10%

RAP28 days

Control 4PDL+

10% RAP1 year

Inertwaste

SNRHWHazardous

waste

Arsenic


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Table 13: Leaching results from granular concrete CL control specimens at 28 days and 1 year

tested in accordance with BS EN 12457-2:2002

Specimen and ageControl 2CL (BRE)28 days

Control 2CL (BRE)

1 year

Control 3CL (SW)28 days

Control 3CL (SW)

1 year

Inertwaste

SNRHWHazardous

waste

Arsenic


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Table 14: Leaching results from granular concrete RCA specimens at 28 days and 1 year tested in

accordance with BS EN 12457-2:2002

Specimen and ageRCARS

28 days

RCARS

1 year

Inertwaste

SNRHWHazardous

waste

Arsenic


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Table 15: Leaching results from granular concrete RA specimens at 28 days and 1 year tested in


Specimen and ageRA1

CC/RAP28 days

RA1CC/RAP1 year

RA2CC/BR28 days

RA2CC/BR1 year

Inertwaste

SNRHWHazardous

waste

Arsenic 0.03 0.04


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Table 16: Leaching results from granular concrete SA specimens at 28 days and 1 year tested in


Specimen and ageSA1FS

28 days

SA1FS

1 year

SA2IBAA

28 days

SA2IBAA1 year

Inertwaste

SNRHWHazardous

waste

Arsenic


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4.2.2 Discussion of resultsConcretes that had been crushed and tested at two different ages from casting (28 days and 1 year) using the

waste acceptance test BS EN 12457-2:2002, gave the results shown in Tables 12 to 16. The findings are as

follows:

All granular crushed concrete specimens exceed the inert WAC for total dissolved solids at both specimenages. Since the aggregates, when tested alone, rarely exceeded the limits for dissolved solids, the level of

dissolved solids can largely be attributed to the cement paste in the concrete.

With a few notable exceptions, the amounts of individual leachate species were generally less in the 1 year

old specimens compared with the 28 day specimens. This is assumed to be due to increased hydrationreactions that will have occurred as the concrete specimens aged, creating a more dense microstructurewithin the concrete, which will have led to greater physical and chemical immobilisation of chemicalcomponents.

Notable exceptions at 1 year, which caused the inert WAC to be exceeded, include mercury in the RA1 andControl 4 specimens (both of which contain RAP), and lead in the SA2 specimen (which contains IBAA).Certain metals (lead, mercury) tend to be more soluble at high pH18, so their appearance in significant

amounts in the leachates from crushed concrete but not those from the aggregates alone, is not surprising.However, this does not necessarily explain the increased leaching at 1 year of age. It is possible that mercury(in the granular concrete specimens containing RAP) and the lead (in the granular concrete specimen

containing IBAA) continued over the 1 year period to dissolve in the water within the pores of the cementpaste (which has a pH 13). During leaching tests, these contaminants could be expected to leach out in

higher concentrations. As concrete is rarely stored for 1 year before use, these results may not berepresentative of concrete in service. Further testing would be needed to examine the leaching characteristics

of concrete submerged in water for a long period. With the exception of Control 3 at 28 days, sulfates were leached to a greater extent at 1 year compared with

28 days, but still did not exceed the inert WAC limit for sulfate. The time dependence is probably due to

changes in the solution phases in the cement paste, causing sulfates to dissolve. The sulfate is largely derivedfrom the Portland cement present.

Concretes containing RAP leached more organic compounds (phenols, TPH) than the RAP alone (whichappears relatively inert). There was also greater leaching of these species after 1 year than after 28 days.This implies that the high pH in the concrete increases the solubility of these organics from the RAP.

Nevertheless, the levels were still relatively low compared with the inert WAC limits.

Chromium is a minor component of Portland cement. The levels of chromium in the leachates from granular

concrete were significant but nevertheless, were not sufficient to exceed the WAC for inert waste.

Overall, assessing concrete in accordance with BS EN 12457-2:2002 appears to be inappropriate for assessing thesuitability of concrete and the aggregates it contains, as it is likely to fail materials already in common use; (for

example, all of the materials failed to meet total dissolved solids criteria, and one of the Cheddar limestone

control specimens exceed the threshold criteria for sulfate). This general unsuitability may be due to the

sensitivity of the test method, which requires a finely ground material with a high surface area. It can be argued

that testing according to BS EN 12457-2:2002 is not a realistic representation of the leaching performance of the

aggregates when in concrete. The higher surface area of the crushed specimen-derived material may not

accurately reflect in-service performance of a concrete monolith.

4.3

Leaching from monolithic concrete specimens

4.3.1

Monolithic concrete specimens tested in accordance with EA NEN 7375:2004

Table 17 to Table 21 show the cumulative 64 day leaching test results for concrete cylinders aged 28 days andafter 1 year and tested in accordance with EA NEN 7375:2004. The results are compared to the Monolith Criteria,

with orange indicating determinand levels below the thresholds for SNRHW, and red indicating determinand levels

below the thresholds for Hazardous waste. There are no thresholds for Inert monolithic wastes so this

assessment cannot be used to determine the general suitability of monolithic materials for use as recycled

aggregates. In some cases, the results may appear higher than in reality, due to the inclusion of one or more

results at a lower limit of detection. For example, 5 specimens tested over the 64 day period all have results at

the lower limit of detection of


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Table 17: Leaching results from monolithic concrete TV and PDL control specimens at 28 days and 1

year (mg/m2)

Specimen name andage

Control 1TVS

28 days

Control 1TVS

1 year

Control 4PDL+ 10%

RAP28 days

Control 4PDL+ 10%

RAP1 year

SNRHWHazardous

waste

Arsenic


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Table 18: Leaching results from monolithic concrete CL control specimens at 28 days and 1 year

(mg/m2) tested in accordance with BS EN 12457-2:2002


Control 2CL (BRE)28 days

Control 2CL (BRE)

1 year

Control 3CL (SW)28 days

Control 3CL (SW)

1 yearSNRHW

Hazardouswaste

Arsenic (As)


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Table 20: Leaching results from monolithic concrete RA1 and RA2 specimens at 28 days and 1 year

(mg/m2) tested in accordance with BS EN 12457-2:2002


RA1CC/RAP28 days

RA1CC/RAP1 year

RA2CC/BR28 days

RA2CC/BR1 year

SNRHWHazardous

waste

Arsenic (As)


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4.3.2 Discussion of resultsThe data for monolithic leaching presented in Tables 17-21 show that the acceptance limits are exceeded for

several elements: arsenic, antimony, selenium, fluoride, mercury, chromium. There is very little difference

between the amounts leached at 28 days and those at 1 year and no consistent differences between concrete

made with recycled, secondary or primary aggregates is apparent. The elements that exceed the threshold limits

(arsenic, antimony, selenium, fluoride, mercury, barium, cadmium and chromium) appear to be derived from

Portland cement and not the aggregates. This conclusion is based on the comparison of these results with those

for the aggregates alone given in Tables 8 and 9.

The SNRHW Monolith Criterion for antimony is exceeded in all cases in the monolithic test. This result can only be

a result of the cement paste present in the concrete since it applies to all the specimens. The Monolith Criteria for

SNRHW, and on occasions Hazardous Waste, are exceeded by the cumulative results of the test, irrespective of

the nature of the aggregate, recycled, secondary or primary. This indicates that EA NEN 7375:2004 may not be

an appropriate procedure to test the leaching characteristics of concrete. As mentioned previously, a 64 day test

would probably not be suitable for compliance testing due to its long duration.

4.4 Turbidity and colour testing

The results from colour testing indicate a slight colouration in some of the concrete leachate specimens relative to

the blanks. However, this is not considered to be significant, as some results from the primary aggregates (for

example, TV, PDL) exceed those for the recycled and secondary aggregates (for example, IBAA, FS). This showsthat in many cases the recycled and secondary aggregates perform no worse than the primary aggregates.

The turbidity results (only available for BRE specimens) given in Table 22, indicate little or no difference between

the turbidity of the test specimen and the blank (the higher the value, the greater the cloudiness or turbidity).

Table 22: Results from colour and turbidity tests

Laboratory SW BRE

Leachate Blank CL IBAA CC PDL Blank CL FS CC CC/BR TV

Colour* (mg/l Pt/Co) < 0.4 < 0.4 1.1 1.2 0.8


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5.0 Conclusions5.1

Leaching performance of materials

The objective of this project was to assess leaching from aggregates, concrete made with recycled and secondary

aggregates and to compare the results with aggregates and concretes made from primary aggregates.

There are no agreed acceptance criteria against which to assess leaching from concrete and aggregates. As a

consequence, the results of the leaching tests have been benchmarked against waste acceptance criteria (WAC),

whilst accepting that the materials are not waste. Inter-laboratory variation of the results has also been assessed.

The results of this study provide evidence that:

The primary aggregates generally performed similarly to recycled and secondary aggregates tested,

Primary and non-primary aggregates exceeded the waste acceptance criteria (WAC) for inert waste in some

respects (Tables 23 and 24),

The concentrations of some species, particularly sulfates and total dissolved solids, appeared high in some ofthe leachates from concretes, but this was generally attributable to the Portland cement present in the

concrete mixes tested, rather than to the aggregates themselves,

The results from control specimens tested by two separate laboratories (using BS EN 1744-3:2002) indicate

that this test method may be sufficiently robust to produce comparable results. It is also completed within 24hours, which is a beneficial feature of any compliance test. It is unfortunate that the test method has littlehistory of use in the UK, does not have agreed acceptance criteria, and may be unfamiliar to many regulators.

Table 23 leaching from aggregates (summary)

Test Aggregates Determinands exceeding inert WAC

(for BS EN 12457-2:2002)

BS EN 12457-2:

2002

Thames Valley aggregate

Cheddar limestone

Recycled asphalt planings

Crushed concrete and crushed brick

Incinerator Bottom Ash Aggregate

Peak District limestone


Spent railway sleeper

Foundry sand

Crushed concrete

None

None

None

None

None

chromium, chloride, total dissolved solids

fluoride

total dissolved solids

nickel

copper, molybdenum, lead, antimony, sulfate, total

dissolved solids

BS EN 1744-3:

2002


Cheddar limestone

Peak District limestone

Foundry sand

Incinerator Bottom Ash aggregate

None

None

None

Nickel

antimony, chloride, sulfate, total dissolved solids(primary aggregates are underlined)

Table 24 leaching from granular concrete specimens (summary)

Aggregates Determinands exceeding inert WAC

(for BS EN 12457-2:2002)

BS EN 12457-2: 2002 Thames Valley aggregate

Peak District limestone + RA planings

Cheddar limestone

Spent railway sleepers

Crushed concrete and RA planings

Crushed concrete and crushed brick

Foundry sandIncinerator Bottom Ash aggregate

total diss. solids

total diss. solids, barium, mercury

total diss. solids, sulfate

total diss. solids

total diss. solids, mercury

total diss. solids

total diss. solidstotal diss. solids, lead


31/45


(concretes made with primary aggregates and no recycled or secondary aggregate content are underlined)

5.2 Suitability of test methods

The results of testing using BS EN 1744-3:2002 and comparing the results to the inert WAC could provide a

method that is suitable for assessment of aggregates; this standard test found primary recycled and secondary

aggregates suitable for use when compared to the WAC for inert granular waste. However, the results of testing

using BS EN 12457-2:2002, (compared to the inert WAC), appears unsuitable to assess aggregates for use in

concrete and crushed concrete made with these aggregates. This test found some recycled, secondary andcommonly used primary aggregates, and concrete containing these aggregates, could be deemed unsuitable

when results are compared to WAC for inert granular waste.

The monolithic leaching test, EA NEN 7375:2004, used in conjunction with WAC, is unsuitable for assessing theappropriateness of concrete or the aggregates that it contains. This test (with comparison to the Monolith

Criteria) failed all concrete specimens, including some containing commonly used primary aggregates.

6.0 Suggestions for further work

A major issue is that there are currently no agreed aggregate-specific compliance criteria against which to assessconstruction materials. There is still a need for debate on whether the WAC for granular wastes is a suitable

means to assess recycled and secondary aggregates in concrete and in other uses. The limited history and

experience in the UK of test methods for assessing leaching from aggregates could be supplemented by:

Wide spread round-robin testing on standard aggregates,

The reporting of results to gather repeatability and reproducibility information,

Further testing of a range of primary, recycled and secondary aggregates to confirm these initial results

Addition of new information from the supplementary testing to the database.

This project has assessed a limited number of aggregate types taken from single locations. Further work could be

conducted to assess a wider variety of materials as well as temporal variations in the materials.


32/45


7.0 References1Reid, JM and Chandler, JWE, Recycling in transport infrastructure, TRL, Crowthorne, 2002.

2Gardner, KH and Eighmy, TT, Recycled materials in transportation applications: Knowledge gaps and research

needs, in Eighmy, TT (ed.); Beneficial Use of recycled materials in transportation applications, Air and WasteManagement Association, Sewickley, USA, 2003.

3British Standards Institution, BS EN 12457-2:2002, Characterisation of waste. Leaching. Compliance test forleaching of granular waste materials and sludges. One stage batch test at a liquid to solid ratio of 10 l/kg for

materials with particle size below 4 mm (without or with size reduction), BSI, London, 2002.

4British Standards Institution, BS EN 1744-3:2002, Tests for chemical properties of aggregates. Preparation ofeluates by leaching of aggregates, BSI, London, 2002.

5Environment Agency, EA NEN 7375:2004, Leaching characteristics of moulded or monolithic building and waste

materials determination of leaching of inorganic components with the diffusion test, EA, Bristol, 2004.

6AggRegain, Environmental Information Sheets, WRAP, Banbury, 2004.(online). Last accessed on 25 March2006 at www.aggregain.org.uk

7Office of Public Sector Information, The Landfill (England and Wales) Regulations 2002, Statutory Instrument2002 No. 1559, OPSI (online). Last accessed 25 March 2006 at www.opsi.gov.uk

8Office of Public Sector Information, The Landfill (England and Wales) (Amendment) Regulations 2004,Statutory Instrument 2004 No. 1375, OPSI (online). Last accessed 25 March 2006 at www.opsi.gov.uk

9Office of Public Sector Information, The Landfill (England and Wales) (Amendment) Regulations 2005,Statutory Instrument 2005 No. 1640, OPSI (online). Last accessed 25 March 2006 at www.opsi.gov.uk

10

WRAP, Quality Protocols for the productions of recycled aggregates from inert waste in England, Scotland andNorthern Ireland, WRAP, Banbury, 2004 and 2005 (available online at www.aggregain.org.uk/quality).

11Official Journal of the European Communities, Council Directive on pollution caused by certain dangerous

substances discharged into the aquatic environment of the community (76/464/EEC), OJEC, Luxembourg, 1976

(online). Last accessed on 25 March 2007, at ec.europa.eu. Note that, since the start of this project, this Directive

has been replaced by Directive 2006/11/EC on pollution caused by certain dangerous substances discharged into

the aquatic environment of the Community (Codified version).

12Statutory Instrument 2000 No. 3184, Water, England and Wales. The Water Supply (Water Quality)Regulations 2000. http://www.dwi.gov.uk/regs/si3184/3184.htm

13

Environment Agency, Model Procedures for the Management of Land Contamination - Contaminated LandReport 11, EA, Bristol, 2004.

14ISO 7027:1999 Water quality -- Determination of turbidity

15British Standards Institution, BS 8500-2:2006, Concrete Complementary British Standard to BS EN 206-1 Part 2: Specification for constituent materials and concrete, BSI, London, 2006.

16Department for Communities and Local Government, Survey of Arisings and Use of Alternatives to PrimaryAggregates in England, 2005 - Other materials, DCLG, London, 2007.

17British Standards Institution, BS 8500-1:2006, Concrete Complementary British Standard to BS EN 206-1

Part 1: Method of specifying and guidance for the specifier, BSI, London, 2006.


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18Van der Sloot HA, Heasman L, Quevauviller Ph, Harmonization of leaching/extraction tests, Elsevier,Amsterdam, 1997.


34/45


Annex A - Leaching assessment criteria

Waste Acceptance Criteria (WAC)

EA WAC related to landfill classification for granular waste (mg/kg dry substance)

Determinand Inert

SNRHW and non-hazardous waste depositedin the same cell with such

wasteHazardous

Mg/kg dry substance

Arsenic (As) 0.5 2 25

Barium (Ba) 20 100 300

Cadmium (Cd) 0.04 1 5

Total Chromium 0.5 10 70

Copper (Cu) 2 50 100

Mercury (Hg) 0.01 0.2 2

Molybdenum (Mo) 0.5 10 30

Nickel (Ni) 0.4 10 40

Lead (Pb) 0.5 10 50Antimony (Sb) 0.06 0.7 5

Selenium (Se) 0.1 0.5 7

Zinc (Zn) 4 50 200

Chloride (Cl) 800 15000 25000

Fluoride (F) 10 150 500

Sulphate (SO4) 1000 20000 50000

Phenol index (PI) 1

Dissolved Organic Carbon (DOC) 500 800 1000

Total Dissolved Solids (TDS)* 4000 60000 100000

pH Minimum 6

Total Organic Carbon (TOC) 30000 5% 6%

BTEX compounds(benzene, toluene, ethyl benzene & xylenes)

6

Polychlorinated biphenyls (PCBs) (7 congeners) 1

Mineral oil (C10 - C40) 500

Poly-aromatic hydrocarbons (PAH) 100

Non-cohesive waste must have a mean in situ bearing ratio of at least 5%.* The value for Total Dissolved Solids is not a requirement but can be used instead of meeting the individual

limits for sulfate and chloride.


35/45


EA Monolith Criteria for landfill

EA WAC related to landfill classification for monolithic waste

Cumulative limit values to 64 days, tested to EA NEN 7375

(mg/m2)Determinand

SNRHW in non-hazardous

landfill

Hazardous waste in

hazardous waste landfill

Arsenic 1.3 20

Barium 45 150Cadmium 0.2 1

Chromium 5 25

Copper 45 60

Mercury 0.1 0.4

Molybdenum 7 20

Nickel 6 15

Lead 6 20

Antimony 0.3 2.5

Selenium 0.4 5

Zinc 30 100

Chloride 10000 20000

Fluoride 60 20000

Sulfate 10000 200

Dissolved organic carbon Not determined Not determined

pH Not determined Not determined

Electrical conductivity Not determined Not determined


36/45


Annex B - Comparison of results between

laboratories using BS EN 1744-3:2002

Selected determinations have been conducted in different laboratories on the same materials (see Tables 2 and

B1). Results from eluate analyses (given in mg/litre or g/l),are shown in Table B2 to B8 below. The red

highlighted cells indicate where there is a significant difference between the results from different laboratories.

Sample distributions according to several different scenarios (intended to show the influence on the results of

different laboratories conducting the leaching step and/or the chemical analysis on the same materials), were

conducted and these are explained in the footnotes to the tables.

The eluate results were generally similar when comparing the results between laboratories that conducted the

leaching step and/or the chemical analysis. There were examples where the results between laboratories by a

factor of four, with the BRE results being smaller than the SW results.

Inspection of the results in Tables B6 and B7 (where eluates generated in the same laboratory have been

analysed in two different laboratories), indicates that there is not a common pattern, (in which results from one

laboratory being higher than that in the other).

Inspection of the results in Table B8 (where two different laboratories generate the eluate and one laboratory

conducts the analysis), BREs results are generally less than the SW results (for the same material).

Interpretation of the results has been made more difficult by the different limits of detection achieved in the

different analytical laboratories. Nevertheless, it is clear that both the laboratory conducting the leaching step and

conducting the chemical analysis have introduced variability into the results.

Table B1: Analysis of aggregate samples (BS 1744-3:2002)

Leachate preparation method BS 1744-3:2002

Aggregate Leachate preparation Leachate analysis

Thames Valley river sand: 0/4 mm (TV) SW SWThames Valley river gravel: 4/20 mm (TV) BRE SW

Crushed Cheddar limestone rock 10/20 mm (CL) SW SW & BRE

Crushed Cheddar limestone rock 4/10 mm (CL) SW SW

Crushed Cheddar limestone rock 4/20 mm (CL) - -

Crushed Peak District limestone rock 4/20 mm (PDL) SW SW

Spent railway sleeper 4/20 mm (RS) SW SW

Crushed concrete 4/20 mm (CC) SW SW

Recycled asphalt planings 4/20 mm (RAP) SW SW

Crushed concrete with crushed brick 4/20 mm (CC/BR) BRE SW

Foundry sand (FS) - -

Incinerator bottom ash aggregate 4/20 mm (IBAA) SW SW & BRE


37/45


Table B2: Results for BS EN 1744-3: 2002 for Spent railway sleeper (RS)

Scenario number 1

BRE Associate Lab 1

BRE Associate Lab 2

SW

SW Associate LabChemical analysed

Units unless

otherwise

indicatedResult LOD Result LOD

Antimony g/l 2.1 1 1.8


38/45


Table B3: Results for BS EN 1744-3: 2002 for Cheddar Limestone (10/20) (CL)

Scenario number 1

BRE Associate Lab 1

BRE Associate Lab 2

SW


Units unless

otherwise


Antimony g/l


39/45


Table B4: Results for BS EN 1744-3: 2002 for Crushed concrete and a high proportion of crushed

brick (4/20) (CC/BR)

Scenario number 2**

BRE Associate Lab 1

BRE Associate Lab 2

BRE Associate Lab 1


Units unless

otherwise


Antimony g/l 1.2 1


40/45


Table B5: Results for BS EN 1744-3: 2002 for Thames Valley gravel (4/20) (TV)

Scenario number 2

BRE Associate Lab 1

BRE Associate Lab 2

BRE Associate Lab 1


Units unless

otherwise


Antimony g/l


41/45


Table B6: Results for BS EN 1744-3: 2002 for Incinerator bottom ash aggregate (4/20) (IBAA)

Scenario number 3

SW

SW Associate Lab

SW

BRE Associate Lab 2Chemical analysed

Units unless

otherwise


Antimony g/l 32


42/45



Scenario number 3

SW

SW Associate Lab

SW


Units

unless

otherwise

indicated Result LOD Result LOD

Antimony g/l


43/45



Scenario number 4

BRE Associate Lab 1

BRE Associate Lab 2

SW


Units unless

otherwise


Antimony g/l


44/45


Table B9: Results for BS EN 1744-3: 2002 for Blank (water)

Scenario number 4

BRE Associate Lab 1

BRE Associate Lab 2

SW


Units unless

otherwise


Antimony g/l


45/45

Written by:

Caroline WeeksFlavie Moulinier

Andrew Dunster

Rachel Harrex

Sumeet BellaraAdam Buttress

Rebecca Hooper

Leaching L0333 AGG079 003 BRE

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