Ea Nen 7375 2004 1026071 Monolitico Holandes

EA NEN 7375:2004
LEACHING CHARACTERISTICS OF MOULDED OR MONOLITHIC

BUILDING AND WASTE MATERIALS
DETERMINATION OF LEACHING OF INORGANIC COMPONENTS

WITH THE DIFFUSION TEST
‘THE TANK TEST’
Based on a translation of the
NETHERLANDS NORMALISATION INSTITUTE STANDARD
Version 1.0
April 2005
Foreword
This standard is for use with the Environment Agency’s guidance on sampling and testing of wastes to
determine acceptance at landfill1. It relates to the determination of the leaching of inorganic
components from moulded or monolithic materials using the diffusion test. It is often referred to as the
tank test.
The Environment Agency has issued a separate standard for the determination of the maximum
potential for leaching of inorganic components from granular waste materials.
The purpose of this diffusion test is to determine the leaching of inorganic components from moulded
and monolithic materials under aerobic conditions. Other parameters that can be deduced from the
test include the extent of surface rinsing and the effective diffusion coefficient that can be used to
estimate the leaching over longer periods.
The diffusion test is not suitable for materials that are soluble during the timescale of the test.
Criteria are set out for this.
This standard is based on a translation of the Dutch leaching characterisation standard NEN 7375
(2004)2. An earlier diffusion test for building materials and wastes was developed in 1995 as NEN
73453. The most important differences between NEN 7375 and NEN 7345 are summarised in Annex B.
European standards for the characterisation of wastes are being developed under the auspices of CEN
Technical Committee 2924, and this standard will be superseded in time by one or more of the
CEN/TC 292-derived standards.
Acknowledgements
The Environment Agency is very grateful to Anton van Santen for the translation of this standard from
Dutch. It would also like to acknowledge the considerable technical advice received from Dr Kathy
Lewin and her colleagues at WRc plc and assistance from David Hall and his colleagues at Golder
Associates (UK) Ltd.
1
See also Guidance on Sampling and Testing of Wastes to meet Landfill Waste Acceptance Procedures, 2005.
2
Leaching characteristics – Determination of the leaching of inorganic components from moulded or monolithic materials with
the diffusion test – Solid earthy and stony materials.
3
NEN 7345: 1995 Leaching characteristics of solid earthy and stony building and waste materials. Determination of the
availability of inorganic components for leaching.
4
Comité Europeén de Normalisation (European Standards Organisation).
EA NEN 7375: 2004 2

Version 1 – April 2005
Contents
Foreword
1. Scope
2. Related Standards
3. Terms and definitions
4. Principle
5. Samples for analysis
6. Reagents
7. Apparatus
8. Procedure
9. Calculation
10. Report
Annex A - Validation of the diffusion test.

Annex B – Differences between NEN 7375:2004 and NEN 7345: 1995.
Annex C - Commentary on the Prescribed Test Pieces and Determination of the Geometric Area.
Annex D - Assessment of a Diffusion Coefficient and Calculation of Derived Values.
Annex E - Graphical representation of diffusion controlled leaching in special cases.
Annex F - Explanation of the calculation of the upper limit for leaching in special cases.
1. Scope
This document provides a test for the determination of the leaching of inorganic components from
moulded or monolithic materials using the diffusion test (the tank test).
A list of materials for which the applicability of the method has been tested, and for which the
precision in terms of repeatability and reproducibility has been determined, is given in Annex A.
2. Related standards
Reference is made to the following standards (and, in brackets, UK ‘Blue book’ (Methods for the
Examination of Waters and Associated Materials, HMSO) equivalent test methods) that should be
adopted when using this interim guidance.
ISO 10523:1994 Water Quality – Determination of pH

(The measurement of Electrical Conductivity and the Laboratory
Determination of the pH value of Natural, Treated and Waste waters.
Standing Committee of Analysts, HMSO, 1978).
ISO 7888:1985 Water Quality – Determination of electrical conductivity
(The measurement of Electrical Conductivity and the Laboratory
Determination of the pH value of Natural, Treated and Waste waters.
Standing Committee of Analysts, HMSO, 1978).
ISO 5667-3:2003 Water Quality – Sampling – Part 3: Guidance on the preservation and
handling of water samples.
BS EN 13370:2003 Characterisation of waste – Analysis of eluates – Determination of
Ammonium, AOX, conductivity, Hg, phenol index, TOC, easily liberatable CN-
and F-.
BS EN 12506:2003 Characterisation of waste – Analysis of eluates – Determination of pH, As, Ba,
Cd, Cl-, Cr VI, Cu, Mo, Ni, NO2-, Pb, total S, SO42-, V and Zn.
EA NEN 7371:2004 Environment Agency standard based on a translation of the Netherlands

Normalisation Institute standard - Leaching characteristics of granular building
EA NEN 7375: 2004 3

and waste materials. The determination of the availability of inorganic
components for leaching. Available from Environment Agency website.
3. Principles
The purpose of this diffusion test is to simulate the leaching of inorganic components from moulded
and monolithic materials under aerobic conditions as a function of time over a period of 64 days.
The test determines the nature and properties of the material matrix under investigation by placing a
complete sample in a leaching fluid (demineralised, pH neutral water) and replenishing the eluate at
specified times. The concentrations of the leached components in the successive eluate fractions are
measured. The pH value at which leaching takes place is determined by the material itself.
On the basis of the diffusion test results, the leached quantity per unit area can be calculated for each
component analysed. Parameters can be deduced from the development of the release of components
over time, including the extent of surface rinsing and the effective diffusion coefficient that can be used
to estimate the leaching over longer periods.
4. Test pieces
The diffusion test requires at least one test piece, the structure, homogeneity and composition of which
are representative for the material or product to be tested. The smallest dimension of this test piece (P)
must be greater than 40 mm and the volume (Vp) in litres must be known.
If the material to be tested is produced in a product format of which the smallest dimension is less than
40 mm, then this product may only be used as a test piece if one side has a geometric surface area A of
at least 75 cm2.
NOTES:
1. To increase the representivity of material under test, it is acceptable to aggregate a number of pieces from a
batch for the diffusion test. The volume (Vp) and the geometric surface area A is then taken as the total
volume and total geometric surface area of the collective pieces.
2. If the diffusion test is being undertaken to determine the effective diffusion coefficient and/or the emission
per unit mass, an extra test piece is required for an availability test. The mass (m) in kg and the density (ρ)
in kg/m3 of test piece must then be known.
5. Reagents
5.1 Demineralised Water

Demineralised water with a maximum conductivity of 1 µS/cm.
5.2 Nitric acid

Nitric acid of analytically pure quality at a concentration c(HNO3) of 1 ± 0.1 mol/l.
6. Apparatus and Equipment

The materials and equipment mentioned below must be checked before use to ensure their proper
operation and absence of interferences that may affect the test results. They must not emit or absorb
any of the components to be determined in the eluate.
The apparatus listed under 6.5 and 6.6 must be calibrated.
EA NEN 7375: 2004 4

6.1 Sealable tank or bucket
Sealable tank or bucket of plastic without softening agents of volume between two and five times the
volume Vp and of dimensions such that the test piece is surrounded by at least 2 cm of water on all
sides.
NOTES:
1. The tank must contain a supporting construction of plastic such that the test piece is surrounded by liquid on
all sides. The test piece can also be suspended on a plastic wire from the lid of the tank or bucket.
2. If the surface of the test piece is partly covered with an impervious layer, use a quantity of water (in l)
between 50 and 200 times the area (in m2) of the uncovered part of the surface of the test piece.
6.2 Filtration equipment

Filtration equipment suitable for filtration at high or low pressure which is consecutively rinsed with
nitric acid (5.2) and demineralised water (5.1).
6.3 Membrane filters

Membrane filters for the filtration equipment (6.2) which have not been previously used, with a pore size
of 0.45 µm.
6.4 Storage bottles

Sealable plastic storage bottles.
6.5 pH meter
pH meter calibrated in accordance with ISO 10523, with a measurement accuracy better than ± 0.05 pH
units.
6.6 Conductivity meter

Conductivity meter calibrated in accordance with ISO 7888, with a readout accuracy better than ± 1%.
6.7 Measuring beaker or balance

A measuring flask with a measurement capacity of at least six times the volume Vp of the test piece and
a measurement accuracy better than ± 1%, or a balance with a capacity of at least three times the
weight of the test piece and a measurement accuracy better than ± 0.1%.
7. Method
The diffusion test is undertaken by successively:
- establishing the requirements for the eluate samples to be analysed in accordance with 7.1;
- determining the geometric area of the test piece intended for the diffusion test in accordance with
7.2;
- performing the diffusion test according to 7.3;
- analysing the eluate according to 7.4.
7.1 Eluate samples

Determine the quantity of eluate needed to analyse the leached components and the way in which the
eluate samples must be stored through the following steps:
a) identify for what components, and by what methods, analyses are to be carried out;
b) check for each component to be analysed whether the eluate will require preservation, and the
requirements for this preservation;
c) determine in the light of the above the minimum quantity of eluate necessary for each component
to be analysed.
EA NEN 7375: 2004 5

In undertaking the above, bear in mind that in order to determine whether the matrix is dissolving it
may be necessary to analyse all eluate fractions for Ca, Cl and SO4. Certainty over this is only
achieved after completion of the entire test (see 7.4).
NOTE:
To prevent changes in the eluate through physical, chemical or biological reactions, the eluate samples must be
preserved and stored as well as possible. Guidelines for surface water and wastewater samples have been
developed in ISO 5667-3. It is recommended that these guidelines be followed for the conservation and storage
of eluates.
7.2 Determination of geometric area A of the test piece

The area of the test piece is determined by measurement of the characteristic parameters of the
geometric surface area.
A distinction is made between:

a) test pieces with a regular, clearly determinable geometric area;
b) test pieces with a completely or partly irregular geometric surface or test pieces that are thinner
than 40 mm;
c) test pieces where no regular side can be determined.
The geometric area of test pieces in a) must be determined according to 7.2.1 if these test pieces
have a minimum dimension of more than 40 mm in all directions measured perpendicular at any point
on the surface.
The geometric area of test pieces in b) must be determined according to 7.2.2.
The geometric surface area of test pieces c) must be determined in accordance with 7.2.3.
NOTE:
For accurate determination of the diffusion coefficient, it is necessary to determine the geometric area of a test
piece precisely and clearly. For this, test pieces or parts of test pieces must be studied for which the geometric
area is easy to determine. In most situations, suitable test pieces can be found. Section 7.2.1 describes the
conditions and procedure for the determination of area. The procedure for selection and determination of usable
areas of test pieces is more complex for test pieces with a (partly) irregular surface. The procedures for this are
given in 7.2.2 and 7.2.3 respectively. For further information, see Annex C.
7.2.1 Regular test pieces for which the entire geometric area is determined
Determination of the geometric area of a regular test piece for which the geometric area of the entire
test piece can be measured clearly.
1. Divide the surface of the test piece into a number of flat or curved parts (units) such that the area of
each unit can be calculated geometrically from characteristic values measured such as length, width,
height and radius.
2. The units specified under 1 must be selected such that the distance between the defined geometric
areas and the material is never greater than 3 mm.
3. Determine the length of the characteristic values with an accuracy of better than 1 mm.
4. Using the characteristic units measured, calculate the geometric area of each of the units selected.
The geometric area A expressed in m2 is the sum of the areas calculated for each of the units.
7.2.2 Determination of the geometric area of test pieces with a partly covered surface
Determination of the geometric area of a test piece for which:
a) the entire geometric area cannot be measured clearly;
EA NEN 7375: 2004 6

b) one or more sides have been produced by sawing or drilling the test piece from a larger element,
and where these sides should not subjected to leaching;
c) one dimension is less than 40 mm.
1. Cover the parts of the surface:

a) for which the geometric area cannot be clearly determined, using a waterproof layer;
b) that have been produced as sawn or drilled surfaces, using a waterproof layer;
c) of a thin test piece (with a thickness of 40 mm or less), using a waterproof layer such that the
uncovered units of the geometric area never have a mutual distance of 40 mm or less measured
perpendicular at any point on the geometrically described surface.
For covering, use a waterproof and good bonding material (for example acrylic resin or paraffin)
applied to the surface of the test piece. Determine the remaining geometric area after hardening of
the resin.
2. Divide the uncovered part of the surface of the test piece into a number of flat or curved parts
(units) such that the area of each unit can be calculated geometrically from characteristic values
measured such as length, width, height and radius.
3. The units specified under 2 must be selected such that the defined geometric areas coincide with
the relevant area of the test piece, where the actual distance between the material and the defined
area of the unit in the case of irregularities in the surface is never greater than 3 mm.
4. Determine the length of the characteristic values with an inaccuracy of less than 1 mm.
5. Using these, calculate the geometric area of each of the units selected. The geometric area A
expressed in m2 is the sum of the areas calculated for each of the units.
7.2.3 Heavily irregular test pieces with no discernible regular side

Determination of the geometric surface area of heavily irregular test pieces using the paper method.
1. Cover each surface of the test piece as tightly as possible with a piece of paper. Use for this a type
of paper that has no obvious absorbent properties.
2. Fold the paper around the edges of each surface of the test piece and tear or cut the paper as
accurately as possible along the folds. Also remove any pieces of paper that may protrude beyond
the surface.
3. Determine the total weight of pieces of paper derived from step 2.
4. Determine the weight of sheet of paper of known area and similar properties to the paper used in
step 1.
5. Determine the surface area of the test piece from the ratio of weights of paper derived in steps 3
and 4.
6. Repeat steps 1 to 5 if the diffusion test is to be based on four or more pieces aggregated together
from a batch. Determine the average of the measurements obtained. This is the geometric
surface area determined according to the paper method.
NOTES:
1. In the determination using the paper method, printer paper and paper for photocopiers (A4 sheets) can be
used. It is important that the paper does not have any strongly water absorbent properties.
2 If the test piece is damp it may be necessary of dry the paper before weighing in step 3.
7.3 Performing the diffusion test

This diffusion test is carried out in eight stages at a temperature that may vary between 18 and 22oC.
EA NEN 7375: 2004 7

Rinse the tank or bucket (6.1) before performance of the test with nitric acid (5.2) and then rinse with
water (5.1). Then place the test piece in the tank or bucket. If more test pieces are placed in the tank
(Section 4), the space between the test pieces must be a minimum of 2 cm.
7.3.1 Stage 1
Fill the tank with a quantity V determined to 1% accuracy (6.7) of water (5.1) such that:
a) if no part of the surface is covered:
2 ×Vp ≤ V ≤ 5×Vp (1)

or
b) if parts of the surface are covered:
50 × A × f ≤ V ≤ 200 × A × f (2)
where:
V is the volume of leaching fluid in litres;

Vp is the volume of test piece P in litres;
A is the uncovered geometric area of the test piece P in m2;
f is a conversion factor: 1 l/m2.
The test piece must be placed such that it is in contact with the water on all sides and the uncovered
part of the test piece is submerged by at least 2 cm.
Seal the tank or bucket.
After 6 ± 0.5 h, drain off all the eluate. This is the fraction from period 1. Do not dry or rinse the test
piece.
Filter over a membrane filter according to the instructions in 7.1 the quantity of eluate required for
analysis (6.2 and 6.3).
For the resulting eluate, measure the pH (± 0.05) (6.5) and conductivity K25 (± 1 %) (6.6).
NOTES:
1. The pH value and the conductivity are required to determine if the matrix has dissolving during the test (see
8.4 and 9.3.3.)
2 The pH value gives an indication of the alkalinity of the test piece, and the change in pH during the diffusion
test gives an indication of the stability of the material being investigated. Large variations in the eluate pH
points towards the material not yet being in equilibrium, i.e. is not yet stabilised.
Transfer the quantity of eluate intended for analysis to the bottles of suitable size (6.4), filling each
bottle with at least 10 ml.
Store the eluate samples using the procedures described in 7.1. If more than 1 ml preservative is
required per 250 ml eluate, the concentrations determined in 7.4 must be corrected for this.
7.3.2 Stages 2 to 8
Immediately after drainage in stage 1 (7.3.1), fill the tank or bucket again with water (5.1). Use the
same quantity V (6.7), determined to ± 1% accuracy, as used in stage 1.
Repeat the procedure described in stage 1 a further seven times as shown in Table 1 (the times apply
from the immersion).
EA NEN 7375: 2004 8

Table 1: Times at which the water must be replenished
Period (n) Time (days)
1 0.25 ± 10%
2 1 ± 10%
3 2.25 ± 10%
4 4 ± 10%
5 9 ± 10%
6 16 ± 1
7 36 ± 1
8 64 ± 1
Determine the replenishment times (the time at which the tank has just been emptied) of each period n,
to 15 minutes accuracy.
On completion of the test, weigh the solid material that may have fallen off the test piece(s) during the
test and remains in the tank. This solid material must first be dried.
If during the replenishment it is found that a relatively large amount of material has fallen off the test
piece(s), it is recommended not to wait until the end of the test but to remove the solid material during
one or more of the replenishments, and to dry and weigh this.
Calculate the weight loss mv (g/m2) of material that has fallen off the test piece during the test (g/A (m2)
where A is the (uncovered) area of the test piece) in two phases:
1) the weight loss mva (g/m2) in Stages 1 to 2 of the test;
2) the weight loss mvb (g/m2) in Stages 2 to 8 of the test.
NOTE:
These two parameters give insight into the characteristics of the material. A relatively large weight loss mva
compared with mvb indicates that the loss is a consequence of the manner in which the test piece has been made
or prepared (for example, loss from an inadequately cured test piece at the start of the test, or loss as the result
of manner of sawing of the test piece). A relatively large weight loss mvb compared with mva indicates the long
term integrity of the material (for example, the ongoing loss of material indicates moderate bonding in a
composite material or loss of effectiveness of the binding agent under the influence of water).
7.4 Analysis of the eluates

Analyse the eluate fractions obtained in 7.3 from periods 1 to 8.
If the measured eluates pH values and conductivities indicate dissolution of the matrix during the test,
then the following calculations must be undertaken, and assessment made whether criteria 1 and 2 are
satisfied. If neither criteria are satisfied, then the components Ca, SO4 and Cl must be determined to
verify whether dissolution has occurred.
1. Calculate the average value of the measured conductivities in periods 5 and 6 (S5-6) in µS/cm.
2. Calculate the average value of the measured conductivities in periods 7 and 8 (S7-8) in µS/cm.
3. Calculate the average pH value in periods 7 and 8 (pH7-8).
Criterion 1
Check if:
S7-8 > 1.5 x Vp/V + 10^(pH7-8 – 11.78) + 10^(2.5 – pH7-8)
EA NEN 7375: 2004 9

where:
V is the volume of leaching fluid, in l;

Vp is the volume of the test piece, in l.
If criterion 1 is not satisfied then the matrix is not soluble, and there is no need to analyse the
components Ca, Cl and SO4.
If criterion 1 is satisfied, continue to criterion 2.
Criterion 2
Check if:
S7-8 > 2 x S5-6
If criterion 2 is not satisfied then the material is not soluble, and there is no need to analyse the
components Ca, Cl and SO4.
If criterion 2 is satisfied, then analyse Ca, Cl and SO4 in all eluates to verify whether dissolution has
occurred (see 8.3.3).
NOTES:
1. A number of standards for chemical analyses of eluate components are available. The European Standards
prEN 13370:2002 and ENV 12506 are intended to define the analytical methods to be used for eluates
obtained from waste characterisation tests. UK ‘Blue Book’ methods (Methods for the Examination of
Waters and Associated Materials, HMSO) would be expected to give similar analysis results.
2 Always analyse the eluate samples within the timescales given in the guidance in ISO 5667-3.
8. Calculation
The measured leaching per eluate fraction, the cumulative leached quantities, the leaching mechanism
occurring, the cumulative leaching per unit area, the surface wash-off and the upper limit of the
leaching of components, for which no diffusion controlled leaching can be determined, are determined
for each component under investigation by successively:
- determining the leaching per eluate fraction as per 8.1;
- determining the measured and derived cumulative leaching respectively as per 8.2;
- establishing the leaching mechanism occurring as per 8.3;
- determining the cumulative leaching per unit area as per 8.4;
- determining the surface wash-off in combination with the diffusion controlled leaching as per 8.5;
- determining the upper limit of leaching for the components for which no diffusion controlled
leaching can be established, as per 8.6.
The above mentioned quantities only have relevance and may only be used if the matrix of the
material does not dissolve. In 8.3.3 a check is made whether this requirements is met.
8.1 Measured leaching of a component per fraction

For each component to be studied, calculate separately the measured leaching per fraction using the
formula:
c ×V
E i* = i (3)
f ×A
where:
E*i is the measured leaching of a component in fraction i, in mg/m2;

EA NEN 7375: 2004 10
ci is the concentration of the component in fraction i in µg/l;
V is the volume of the eluate in l;
A is the surface area of the test piece in m2;
f is a conversion factor: 1000 µg/mg.
The concentration ci specified in formula (3) is the concentration originally present in the eluate; the
measured value determined according to Section 7.4 must be corrected for the quantity of preservative
added in Section 7.3 if this is more than 1 ml per 250 ml eluate.
If the concentration of a component in a specified eluate fraction is below the lowest limit of analytical
determination, two calculations must be carried out for the component. The upper limit of E*i is
calculated by equating ci in formula (3) with the lowest limit of determination; the lower limit of E*i is
calculated by setting ci in formula (3) to 0.
8.2 Measured and derived cumulative leaching of a component
8.2.1 Measured cumulative leaching

For each component to be analysed, calculate separately the measured cumulative leaching ε*n in each
of the periods n =1 to N, where the period n=1 lasts from the start of the test to the first replenishment
time (comprises fraction i=1), period n=2 from the start of the test to the second replenishment time
(comprises fractions 1 + 2), etc. Carry out this calculation as:
n
ε n* = ∑ Ei* for n=1 to N (4)
i =1
where:
ε*n is the measured cumulative leaching of a component for period n comprising fraction i=1 to n, in
mg/m2;
E*i is the measured leaching of the component in fraction i in mg/m2;
N is the number of periods equal to the number of specified replenishment times (N = 8).
The calculation method is explained as in Figure 1 below.
8.2.2 Derived cumulative leaching of a component

For each component to be analysed, calculate separately the derived cumulative leaching εn in each of
the periods n=1 to N, where a period n lasts from the start of the test to the nth replenishment time
(comprises fractions i=1 to n).
Carry out this calculation as follows:
ε n = ( Ei* × ti ) /( ti − ti −1 ) for n=1 to N (where i =n) (5)
where:
εn is the derived cumulative leaching of a component for period n comprising fraction i=1 to n, in
mg/m2;
E* i is the measured leaching of the component in fraction i, in mg/m2;
ti is the replenishment time of fraction i, i.e. time at end of fraction i, in s;
ti-1 is the replenishment time of fraction i-1, i.e. time at start of fraction i, in s.
NOTES:
1. The measured cumulative leaching ε*n always includes the measured leaching of previous periods. This
means that any deviations in a period (for example wash-off effects) affect the following periods that can
make interpretation difficult.
EA NEN 7375: 2004 11

2 The derived cumulative leaching εn determines only the cumulative leaching up to and including period i on
the basis of the measured leaching in period i. These values can be used to assess whether the leaching is
determined by diffusion (see Section 8.3).
Figure 1: Diagrammatic overview of terms used in this standard in determining the

leaching behaviour of a test piece.
The fractions i=1 to i =N indicate the successive eluate fractions;
the period n=x corresponds to the sum of the number of fractions i=1 to i=x.
8.3 Determination of the leaching mechanism(s) occurring in the diffusion test

Based on the leaching of components as set out in 7.4, establish whether the matrix of the test piece is
dissolving during the conduct of the test. If this is not the case, then for all individual components
determine whether leaching is diffusion controlled or whether other leaching mechanisms also
contribute.
Carry out the procedure in this section for each of the components to be studied.
NOTE:
To support and monitor the further assessment and calculation of the leaching behaviour, it is recommended that
the cumulative leaching determined in Sections 8.1 and 8.2 be shown graphically (see Annex E). For this, plot for
each individual component the logarithm of the derived cumulative leaching εn against the logarithm of the time ti for
n=1 to N in order to allow a visual inspection of the measurement data. On the same graph also plot the logarithm
of the measured cumulative leaching ε*n.
8.3.1 Definition of incremental periods

Group the eluate fractions collected in the periods 1 to 8 as follows:
EA NEN 7375: 2004 12

Order Eluate fraction Increment a-b
1 Fractions 2 to 7 Increment 2-7 incl
Analyse the leachate values according to the procedure in 8.3.2, beginning with increment 2-7, followed
by increment 5-8 and so on. Use this order for each component.
NOTES:
1 The method to establish whether the leaching mechanism is diffusion controlled is built up as follows:
a) Firstly, the eluate fractions obtained and analysed in periods 1 to 8 are divided into increments that are
long enough to establish the leaching mechanism.
a) For all components to be determined, and for each of the divided increments in a), the concentration
factor (CF), the slope (rc) of the linear regression line of log ε versus log t and the standard deviation of
the slope (sdrc) are determined and recorded in a table (see 8.3.2).
c) Subsequently, on the basis of these values, check that the matrix does not dissolve (see 8.3.3). If the
test piece (the matrix) does dissolve, then the leaching from this test piece can not be determined with
the diffusion test.
d) If the matrix does not dissolve, then for all components, per increment, a check is made whether the
quantity of diffusion controlled leaching can be determined. The first increment in the order given in
a) for which the quantity of diffusion controlled leaching can be determined is the “leaching
mechanism determining increment”.
e) Subsequently, it is determined whether, in addition to diffusion, other leaching mechanisms are
involved.
f) If for certain components no diffusion controlled leaching can be established (and there is no suggestion
of the matrix dissolving), then an estimate can be made of the upper limit of leaching.
2 Increment 2-7 is considered as a “total increment” for the entire diffusion test. The first fraction is not
included in order to eliminate interpretative errors in the analysis due to wash-off effects. The last fraction
is also not included in the total increment to eliminate as far as possible depletion of a certain component
during the test.
8.3.2 Incremental analysis per component

For each component to be studied, undertake an incremental analysis as follows:
Step 1:
For each increment a-b determine the concentration factor CFa-b:
CFa-b = mean concentration in the increment (6)

lowest limit of determination
If in all the fractions in the increment a-b, the measured concentrations for the component under
investigation are all higher than the lowest limit of determination for that component, and CFa-b = 1.5,
then continue to Stage 2. If this is not the case, then for this component no leaching mechanism can be
determined in this particular increment.
NOTE:
If for an increment the factor CFa-b for the component under investigation is less than 1.5, the values measured in
that increment are too low to allow determination of the leaching mechanism. Also, if in one of the fractions of the
increment the concentration is lower than the lowest limit of determination, then it cannot be proved whether the
leaching is diffusion controlled.
EA NEN 7375: 2004 13

Step 2:
Using linear regression of the log εn - log ti relation (with i =n), determine for each increment the slope
rc and the associated standard deviation, sdrc calculated from the regression analysis.
The concentration factors, slopes and standard deviations can be given clearly as shown in Table 2 to
support and simplify the assessment and further processing of the test results.
Table 2: Overview of concentration factors, slopes and standard deviations as determined

in the following increments.
Increment a-b CFa-b rc Sdrc

Increment 2-7
Increment 5-8
Increment 4-7
Increment 3-6
Increment 2-5
Increment 1-4
8.3.3 Determining whether the matrix dissolves

The determination of the leaching mechanism and the quantification of the leaching per component only
have meaning if the matrix of the material does not dissolve. In 7.4, two criteria are used examine
whether, in principle, this could be the case.
If in 7.4 both criteria are not satisfied, then the material does not dissolve. In this case, proceed to
8.3.4.
If in 7.4 both criteria are satisfied, proceed then on the basis of the values for Ca, Cl and SO4
determined in 8.3.2 to evaluate whether criterion 3 is satisfied.
Criterion 3:
For at least 2 of the 3 above mentioned components, check whether CF5-8 > 3.0 and rc5-8 > 0.8.
If criterion 3 is not satisfied, then the matrix does not dissolve. In this case, proceed to 8.3.4.
If criterion 3 is satisfied, then the matrix does dissolve. In this case the leaching from this test piece
cannot be determined through the diffusion test.
NOTE:
This criterion will be satisfied principally by gypsum product and materials with a high salt concentration.
8.3.4 Determining whether the leaching of the different components is diffusion

controlled or whether other leaching mechanisms are involved
On the basis of the concentration factors and slopes calculated in 8.3.2, it can be determined which
leaching mechanism(s) are involved in the release of different components from the test piece. A
precondition for this is that the standard deviation of the slope must meet certain requirements. With
fully diffusion controlled leaching, the slope is exactly 0.5.
The significance of the slope of the different increments is summarised in Table 3.
Table 3: Significance of slopes of the different increments.
EA NEN 7375: 2004 14

Increment a-b Slope, rc
≤ 0.35 > 0.35 and ≤0.65 > 0.65
Increment 2-7 Surface wash-off Diffusion Dissolution

Increment 5-8 Depletion Diffusion Dissolution

Increment 1-4 Surface wash-off Diffusion Delayed diffusion or
dissolution
Step 1:
Determine per component for all increments, in the order given in Table 3 beginning with increment 2-7,
if the leaching mechanism is diffusion controlled on the basis of the following criteria. The first
increment for a component for which the quantity of diffusion controlled leaching can be established is
deemed the “leaching mechanism determining increment” for that component.
Criteria for diffusion controlled leaching in increment a-b
CFa-b ≥ 1.5 sdrc ≤ 0.5 0.35 < rc ≤ 0.65
If the above criteria are satisfied, then the diffusion controlled leaching of the component concerned can
be calculated using the formulas in 8.4.
If, as well as diffusion controlled leaching, there is also an indication of surface wash-off in increment 1-
4, then this surface wash-off can be quantified using the formulas in 8.5.
Step 2:
If for certain components diffusion controlled leaching cannot be established in any of the increments
(and the material does not dissolve according to the criteria in 8.3.3), then for that component an
upper limit for leaching is determined. For this, proceed to 8.6, in which formulas are given for
various situations dependent on the controlling leaching mechanism.
NOTE:
In Annex E graphical representations are given of each extreme case of leaching. Depletion events are indicated
in Figure E2, surface wash-off in Figure E4 and chemical changes in the material in Figures E3, E5 and E6.
8.4 Calculation of the diffusion controlled leaching of a component per unit surface area
The calculation of leaching of a component per unit surface area must be undertaken in all cases, where
the diffusion controlled leaching has been established by the increment analysis in 8.3.4.
The derived leaching of a component per unit surface area over an arbitrary time interval can be
determined by the formula:
1
 b E* 
1+ b − a
ε x, y = { }
t y − tx  ∏ i
 (7)
i = a ti − ti − 1 

where:
εx,y is the derived leaching of a component in the time period tx and ty, in m2/s;
EA NEN 7375: 2004 15

tx is the start time of the interval measured from the start of the test, in days;
ty is the end time of the interval measured from the start of the test, in days;
ti is the end time of fraction i, which is part of the increment a-b, for which diffusion has been
established, measured from the start of the test, in days;
ti-1 is the start time of fraction i, measured from the start of the test, in days. This is part of the
increment a-b, for which diffusion has been established..
a,b are dimensionless indices by which an increment a-b is indicated for which a diffusion mechanism
is established.
NOTES:
1. The product function in (7) is a measure for the average leaching rate, taking into account the diffusion
controlled nature of the leaching process. The leaching is corrected by the square root of the times. In
practice, this method of calculation leads to a calculated average negative logarithm of the effective
diffusion coefficient (pDe). For the determination of the average effective diffusion coefficient De, see
Annex D1.
2. If, for example, a diffusion controlled mechanism is established in increment 2-7, then the product function
takes the values a=2 and b=7:
 7 6 =
{ }
1
∏ U i U 2 ×U 3 ×U 4 ×U 5 ×U 6 ×U 7 6 (8)
i =1 
where:
Ei*
Ui =
t i − t i −1
Calculate for each component under investigation separately the derived cumulative leaching per unit
are over 64 days, ε64, with the formula:
1
 b Ei* 1+b−a
ε 64 = 64  ∏  (9)
i = a ti − ti − 1 
where:
ε64 is the derived cumulative leaching for a component over 64 days, in mg/m2;
ti is the end time of fraction i for which diffusion has been established, measured from the start of
the test, in days;
ti-1 is the start time of fraction i for which diffusion has been established, measured from the start of
the test, in days;
a,b are dimensionless indices by which an increment a-b is indicated for which a diffusion mechanism
is established.
Calculate also for each component under investigation separately the measured cumulative leaching per
unit surface area over 64 days ε*64 using the formula:
N
ε 64
*
= ∑ E i* (10)
i =1
where:
ε*64 is the measured cumulative leaching for a component per unit surface area over 64 days, in
mg/m2;
E*i is the measured leaching of the component in fraction i, in mg/m2;
EA NEN 7375: 2004 16

N is the number of periods, equal to the number of prescribed refreshing intervals (N=8).
If the measured cumulative leaching over 64 days (ε*64), calculated using formula (10) is smaller that
the derived cumulative leaching calculated using formula (9) and also the slope of increments 3-6 and
4-7 are both smaller than 0.35, then the measured cumulative emission over 64 days is considered to
be the upper limit of leaching.
8.5 Quantifying the surface wash-off in combination with diffusion-controlled leaching

The surface wash-off of a component per unit surface area can only be determined where the
incremental analysis in 8.3.4 has established that the leaching of that component is diffusion controlled.
If surface wash-off is indicated in the first two factions of increment 1-4 (rc ≤ 0.35) whilst in one or more
of the following increments diffusion controlled loss is accepted, then the amount of surface wash-off
(εwash,1-2) in mg/m2 is given by:
ε wash,1−2 = E1* + E 2* − ε 64 × 1 / 64 (11)

where:
εwash,1-2 is the washed-off quantity of the particular component, in mg/m2;

E*1 is the measured leaching of that component in fraction 1 (1/4 day), in mg/m2;
E*2 is the measured leaching of that component in fraction 2 (1 day), in mg/m2;
ε64 is the calculated leached quantity of the particular component over 64 days, in mg/m2
calculated from formula (9).
NOTE:
See Annex E, figure E4 for a graphical representation of this type of leaching.
8.6 Determination of the upper limit for leaching of components for which no diffusion
can be established
The calculation of the upper limit for leaching of a component per unit surface area can only be
undertaken when, according to 8.3.4, leaching of the particular component is not diffusion controlled
and, according to 8.3.3, the matrix does not dissolve.
NOTE:
If the matrix does not dissolve, then for certain components for which diffusion cannot be established by the
increment analysis, an estimate can still be made of the long term leaching by applying the formulas for diffusion
controlled leaching.
The calculations must be considered in the order set out in the following paragraphs.
8.6.1 The concentration factor CF1-8 is less than 1.5

If the concentration factor CF1-8 is less than 1.5, then the upper limit of the cumulative emission over
64 days is calculated as follows:
ε64 = ε*1-8 (12)
where ε*1-8 is calculated from 8.1 and 8.2.1, where ci in Formula (3) is set equal to the lowest limit of
determination.
NOTE:
If the concentration factor CF1-8 is less than 1.5 then the average concentration for the “total increment” is less
than 1.5 times the lowest limit of determination.
The upper limit for leaching over a period T from the beginning of the leaching is calculated from:
EA NEN 7375: 2004 17

ε T = ε 1*−8 × T / 64 (13)
where:
εT is the upper limit of the leaching of a component over a period T, in mg/m2;

T is the duration of the period, in days.
8.6.2 Surface wash-off followed by low concentrations in the subsequent fractions

If through the increment analysis in 8.3.4 it is found that surface washing has occurred, followed by
low concentrations on the subsequent fractions, then the upper limit for diffusion over a time period T
from the start of leaching is calculated from:
T − 1
ε T = ε 1*−2 + ε 3*−8 × (14)
64 − 1
where:

ε*1-2 is the measured cumulative leaching over the increment 1-2, in mg/m2;
ε*3-8 is the measured cumulative leaching over the increment 3-8 (upper limit, see 8.1), in mg/m2;
NOTE:
Formula (14) for the wash-off applies if in increment 1-4 the slope is less than 0.35 and additionally that the
concentrations are well measurable, whilst the concentrations in increment 5-8 are not so measurable.
Extrapolation of the measured leaching according to a diffusion controlled leaching will overestimate the true
leaching. It is also not correct to extrapolate the initial wash-off using the formula for diffusion controlled
leaching; in stead the wash-off should be added to the diffusion controlled leaching.
8.6.3 Possible depletion/changing chemical form

If the increment analysis in 8.3.4 reveals that for a component that in at least two of the increments
2-5 and/or 3-6 and/or 4-7 and/or 5-8 the slope is less than 0.35 and the concentration factor is
greater than 1.5, then this indicates that depletion of this component may have occurred.
NOTE:
1. There are also indications of depletion if, after initial wash-off, significant concentrations are measured in
the extracts in following the periods (as opposed to the situation described in 8.6.2). Extrapolation of the
cumulative measured leaching will then overestimate the actual leaching. It is, however, not correct to
include the initial wash-off in the formula for the diffusion controlled leaching.
2. Inert components are distinguishable by having the lowest pDe values in the matrix under consideration,
whilst the remaining components always have a higher pDe value. This means that depletion always occurs
earlier with inert components than with the other components. The appearance of an rc<0.35 in such a
case can be explained by the fact that chemical conditions change, as a result of which a step change
occurs to, for example, a different diffusion level, or that a mobile chemical form becomes depleted whilst a
different leachable form of that component remains (more strongly) bonded in the matrix.
The upper limit for leaching over a period T from the start of leaching can then be calculated by the
formula:
T − 1
ε T = ε 1*−2 + ε 3*−8 × (15)
64 − 1
where:

ε*1-2 is the measured cumulative leaching over the increment 1-2, in mg/m2;
ε*3-8 is the measured cumulative leaching over the increment 3-8 (upper limit, see 8.1), in mg/m2;
EA NEN 7375: 2004 18

8.6.4 Dissolution
If the slope for the a particular component for the total increment (2-7) is greater than 0.65 (see
8.3.4 Step 1), the leaching over 64 days is calculated as:
ε64 = ε*1-8 (16)
ε*1-8 is determined as set out in 8.1 and 8.2.1, where ci in formula (3) in 8.1 is given the value of the
lowest limit of determination if the concentration of a component in a fraction is lower than the lowest
limit of determination.
The upper limit of leaching over a period T from the start of leaching is then:
ε T = 2 × ε 1*−8 × T / 64 (17)
NOTE:
If the slope is greater than 0.65 then there is a possibility of dissolution of the component. This appears contrary
to the finding that the test piece is not dissolving. This, however, need not be the case. It can be concluded
that, viewed from the leaching mechanism of the matrix, the dissolution of the particular component has no
permanent character. It is even possible that dissolution is only occurring from the outer layer of the test piece.
The slope can also be greater than 0.65 if at low concentrations the influence of other components is relatively
large.
8.6.5 Large spread in measured concentrations

No determination of the slope is possible in 8.3.4 step 1 where the measured concentrations exhibit a
wide spread (sdrc>0.5). In this case the leaching over 64 days is calculated by the formula:
ε64 = ε*1-8 (18)
ε*1-8 is determined as set out in 8.1 and 8.2.1, where ci in formula (3) in 8.1 is given the value of the
lowest limit of determination if the concentration of a component in a fraction is lower than the lowest
limit of determination.
The upper limit of leaching over a period T from the start of leaching is then:
ε T = 5 × ε 1*−8 × T / 64 (19)
where:

ε*1-8 is the measured cumulative leaching over the total duration of the test, in mg/m2;
NOTE:
Research has been conducted to investigate how large the error in the value of pDe could be when sdrc>0.5. In
that case the slope rc could rise to 1.5 so that the value of pDe would be a whole 1 log (m2/s) lower. This is
equivalent to a 10 fold overestimate of the diffusion coefficient, which means at least a three fold overestimate of
the leaching. Because the value of pDe within the period of the diffusion test can decrease even further due to
changes in the chemical conditions (for example, through the leaching of lead from a reducing material), a factor
of 5 is introduced in the formula for εT to give the assumed upper limit.
Table 4: Calculation of the upper limit of leaching of a component in special

circumstances
Description Criteriaa Formula for calculating εT

1) Measured, average CF1-8<1.5 ε T = ε 1*−8 × T / 64 (13)
concentration in all fractions is
EA NEN 7375: 2004 19

low
2) Wash-off in the first two steps, CF ≥ 1.5 and rc < 0.35 for T − 1 (14)
after which measured increment 1-4, and CF < 1.5 for ε T = ε 1*−2 + ε 3*−8 ×
concentrations are low increment 5-8 64 − 1
3) Possible depletion of different rc < 0.35 and CF ≥ 1.5 for at T − 1 (15)
chemical forms least two of the increments 2-5 ε T = ε 1*−2 + ε 3*−8 ×
and/or 3-6 and/or 4-7 and/or 64 − 1
5-8
4) Dissolution during increment rc > 0.65 for increment 2-7 ε T = 2 × ε 1*−8 × T / 64 (17)
2-7
5) Large spread in all increments sdrc > 0.5 for increments 3-6, ε T = 5 × ε 1*−8 × T / 64 (19)
4-7 and 5-8
a
The parameters have the following meanings:
CFa-b is the concentration factor in increment a-b
rc is the slope of the relevant increment
sdrc is the standard deviation of the slope of the relevant increment
εT is the upper limit of leaching of a component over period T, in mg/m2
*
ε a-b is the measured cumulative leaching over the relevant increment a-b, in mg/m2
T is the duration of the period, in days
8.6.6 Summary of situations in which the upper limit of leaching can be determined
Table 4 provides a summary of the formulas used to calculate the upper limit of leaching where there
is no possibility of diffusion and the matrix is not dissolving. Further information on the exceptional
cases in Table 4 are given in Annex F.
9. Report
The report must contain the following data at least:
- a reference to this standard, indicating: “in accordance Environment Agency standard EA NEN
7375:2004";
- the data necessary for identification of the test piece(s);
- source and specifications of the test piece(s);
- the nature of the material studied;
- the temperature range within which the leaching test was performed;
- the pH of the eluates collected, rounded to 0.0.5 pH-unit;
- the conductivity of the eluates collected rounded to maximum 1 significant figure;
- the components analysed and the lowest limits of determination of the components in the eluate;
- the means by which the eluates have been preserved and stored until the time of analysis;
- all concentrations measured, rounded to maximum 2 significant figures;
- the quantity of preservative added in Section 7.3 if this is more than 1 ml per 250 ml eluate;
- the amount of material fallen off the test piece(s) during the test;
- the slopes and corresponding standard deviations of all increments;
- the start and end points of the leaching mechanism-determining increment, if the leaching of the
relevant component is diffusion controlled;
- the quantity of the components tested available for leaching;
- the results of the investigation into the (non-) dissolution of the test piece(s);
- the calculated cumulative leaching of the components tested over 64 days (ε64), in mg per m2;
- the measured cumulative leaching of the components tested over 64 days (ε*64), in mg per m2;
- the evaluated possible surface wash-off of the components tested, in mg/m2;
EA NEN 7375: 2004 20
- the calculated upper limit in possible special circumstances of leaching of one or more
components, in mg/m2;
- the eventual weight loss during the test, in mg/m2;
- the duration of the investigation.
If the diffusion test is not carried out fully in accordance with this standard, all deviations from the
prescribed procedures must be indicated in the report, giving the reasons.
EA NEN 7375: 2004 21

Annex A
Validation of the Diffusion Test
In developing the Dutch Standard, NEN 7375, a round-robin test was undertaken with 10 laboratories
on 3 types of material to establish the precision of the diffusion test in terms of repeatability and
reproducibility. The following is taken from the discussion presented in NEN 7375.
The error in the end result of a leaching test is composed of contributions from:
- The origin of the material (variations in the production process);
- The method of sample taking (differences in representativeness);
- The sample pre-treatment (variations in the preparation of the test piece for the leaching test);
- The leaching test itself;
- The chemical analysis (error in the determination of concentration in the eluates);
To establish the precision of the diffusion test, the contribution of these sources of error were
minimized through the experimental design. Therefore, in the validation study the following starting
points were used.
- Components that can be very inhomogeneous in certain materials were not included in
determining the precision.
- The samples were all taken from one batch and the sample preparation was performed in one
session.
- All chemical analyses were carried out by one laboratory.
- The precision was only determined for components for which the error in the chemical analysis
was sufficiently small (relative standard deviation in repeatablility nominal less than 5%). For
larger errors in the concentration measurement the precision of the analysis would dominate the
precision of the leaching test result too much.
The test pieces examined relate to three different types of moulded materials. The table below gives
an overview of the materials used and the components tested:
Table A.1: Investigated materials and components
GRAIN SIZE CLASS MATERIAL TESTED COMPONENTS TESTED1)

Moulded Fly ash/cement mix Na, Ba, Mo, SO4, V
Sand lime brick with coal dust fly
Moulded Na, As, (Ni), Se*, SO4, (V)
ash
Moulded Building brick Na*, As, V
1) All elements in brackets and marked * in Table A.1 were measured but not included in
determining the median and the range of the overall precision values, because:
- the error in the concentration measurement was too large (marked with brackets);
- for the determination of the repeatability less than 5 laboratories where found for which in
both duplicate leaching tests using the procedure 8.3 clearly a leaching mechanism could be
determined (marked *). For the determination of the reproducibility always the results of at
least 8 laboratories could be used.
The round-robin on the above materials and components combinations have the following values for
standard deviations for repeatability (Sr) and reproducibility (SR) in the diffusion test.
EA NEN 7375: 2004 22

Median Range
Sr in the determination of ε64 13% 8% to 18%
SR in the determination of ε64 16% 10% to 42%
Sr in the determination of pDe 0.11 0.07 to 0.17
(unit: -log[m2/s])
SR in the determination of pDe 0.19 0.12 to 0.40
(unit: -log[m2/s])
In general no clear dependency of Sr and SR on the material type was found.
NOTES:
1 No correction is made for the contribution of the analytical error, because ε64 and pDe are calculated using a
diffusion model through a fitting procedure. In general, the influence of the analytical error is of minor
importance in the above values of the precision.
2 The precision values for the diffusion test are corrected for the error in the availability test result.
3 The values for Sr and SR shown are only appropriate for material-component combinations for which:
- the contribution of the relative standard deviation in the concentration measurement is less than 5%.
- at least 5 data sets are available for which clearly a diffusion controlled leaching mechanism could be
determined.
All material-component combinations in table A.1 that are not marked with brackets or *, satisfy these two
requirements.
The mentioned median values and ranges for Sr and SR are indicative values of the attainable
precision, if the diffusion test is performed according to this standard and also the requirements
mentioned in note 3 above are met. In particular, a higher degree of uncertainty may apply to
materials which are very heterogeneous and/or to components for which the concentration
measurements in the eluate causes problems (due to e.g. low levels).
EA NEN 7375: 2004 23

Annex B (Informative)
Differences between NEN 7375 and NEN 7345
The repeatability and reproducibility of the diffusion test according to NEN 7345, established in the
round-robin validation test (see Annex A of this standard), proved less good than desired. For this
reason, under the auspices of the Action Programme Normalisation and Validation of Environmental
Measurement Methods a project Improvement of the quality of three normalised leaching tests in the
NEN-7340 series (ANVM-216,) was undertaken. In that project, consideration was also given to the
developments on European harmonisation under the auspices of the CEN committee TC 292. Most of
the changes proposed in ANVM-216 for undertaken diffusion tests have been adopted by the
standards committee 390 011 and recommended for adoption in the standard. The existing standard
NEN 7345 will not be revised because at this time CEN/TC 292 diffusion tests for earthy and stony
waste materials are being developed, so there is a “stand still” on the development of national
standards on the same subject. At the same time, it is expected that NEN 7345 will be replaced by
one or more of the CEN/TC 292 developed standards for diffusion tests. Because in the meantime
there is still a need for a generally applicable diffusion test, in which the recommendations from
project ANVM-216 are adopted, a new standard (NEN 7375) has been brought out with a wider
applicability than CEN is considering, namely all earthy and stony materials.
The most important changes from NEN 7345 that have been brought forward in NEN 7375 are as
follows:
1. The applicability is generalised to earthy and stony materials (as opposed to just earthy and
stony building materials and wastes).
2. The diffusion test must in future be conducted with pH neutral instead of acidified water. The
most important reason for this is that this will be incorporated in the standards being developed
in CEN/TC 292.
An additional advantage of this is that the use of pH neutral water is that, in the case of materials
with a low buffering capacity, large differences in the initial leaching by leaching fluid with an
imposed pH=4 is overcome. This effect is much less with the use of pH neutral water. A
separate literature and model study has considered the consequences of using neutral instead of
acidified water. This has found that the difference in leaching results are possibly only observed
in materials with a very low buffering capacity. Examples of this are vitrified slag, some industrial
slags and sintered products, such as artificial gravel and brick. The differences in leaching for
these types of material also appear to be very small (and only observed for metals); under
normal laboratory conditions these are barely discernable.
3. The “paper method” has been introduced for the determination of the geometric surface area of
highly irregular test pieces.
4. The determination of the leaching mechanism during the diffusion test is more systematically
described and elaborated
5. The leaching volume is smaller, thus the required determination limit in testing to (regulatory)
standards is easier to achieve analytically.
6. The “diffusion controls the leaching from the matrix” as criterion for applicability of the standard
is replaced with the criterion “no dissolution of the matrix”.
7. For the calculation of the cumulative leaching per unit surface area, it is no longer necessary to
undertake the availability test according to EA NEN 7371, since the value of the diffusion
coefficient derived from that test has been eliminated from formulas (7) and (9) for the
arithmetic leaching of a component over a given interval (εx,y) and over a period of 64 days (ε64),
respectively.
EA NEN 7375: 2004 24

8. For the determination of the average negative logarithm of the effective diffusion coefficient per
component, it is still necessary to undertaken the availability test according to EA NEN 7371.
This determination is set out in an informative annex (Annex D.1).
9. For the determination of the leaching per component, for which according the procedure in 8.3.4
no diffusion controlled leaching can be established, whilst according to 8.3.3 it is established that
the matrix does not dissolve, a calculation method is given to establish the upper limit of
leaching.
EA NEN 7375: 2004 25

Annex C
Commentary on the Prescribed Test Pieces and Determination of the Geometric Area
C.1 It is recommended that at least three test pieces are available, two of which meet the
dimensional requirements, as supplementary tests may be found necessary. The third test
piece may be necessary for performance of an availability test according and is finely ground for
this.
C.2 In general, diffusion is determined on the basis of leaching from the entire test piece. This may
be a sample of an original building element (e.g. a brick) or a test piece moulded in a special
mould from the material to be tested (e.g. a Marshall slab of asphalt concrete).
C.3 To prevent practical problems in the performance of the test, it is recommended that an upper
limit of 300 mm be set for the largest dimension of the test piece.
C.4 To prevent the leaching diminishing during the diffusion test due to depletion of a component,
the smallest dimension of the test piece must be larger than 40 mm. For components with
great mobility, during the test some depletion can occur if the smallest dimension lies in the
area of the lower limit of 40 mm. Depletion of mobile components can then be prevented by
using a slightly larger test piece.
C.5 Certain building materials are produced as standard with a thickness of less than 40 mm such
as slate roof covering, ceramic roof tiles, thin tiles, hollow bricks or garden tiles. Usually the
required strength of these products implicitly leads to materials with such a high pDe value that
no depletion phenomena occur during the diffusion test. For an optimum result in the diffusion
test, such thin test pieces must be covered on one side.
C.6 For partial covering of a test piece with an impervious layer, material must be used that has no
disruptive influence on the diffusion process by the release, absorption or (delayed)
transmission of components to be studied. It has appeared that acrylic resin is a suitable
impervious material for leaching tests on inorganic components with the diffusion test. The
usability of other impervious materials is still being studied.
C.7 The test piece can be prepared in the laboratory under conditions that correspond to those
found in practice. Preference is however given to the product as used in practice. The test
piece can also be part of the manufactured product unless surface treatment causes significant
differences in the surface structure or the ground surface. The latter can be compensated by
covering the surface concerned such that no rinsing or diffusion from the surface occurs during
the test.
C.8 If, after production, the product must harden for a specific period before reaching the strength
required in practice, it is important for the interpretation of the results of the diffusion test to
bear in mind that also the leaching behaviour can change during the period that hardening
takes place.
C.9 Some test pieces are sawn or drilled out of a larger whole, for example a drilling core from a
road surface. The sides formed by the sawing or drilling may have leaching extent not shown
by the unworked surfaces. The worked surfaces must be covered in accordance with the
procedure in Section 7.2.2. For a number of materials, it has been found that the diffusion
differs little or not at all from the diffusion from the unworked part. In these cases, the sawn or
drilled surfaces can also be included in determining the diffusion.
C.10 If the geometric area cannot be clearly and easily established for the entire surface, the test
can often be carried out on part of the outer surface. Examples of materials where part of the
surface must be covered are coarse slag and cobbles. Often one or more test pieces are
selected from a representatively assembled sample of such slag or cobbles, for which large
parts have an area that can be easily determined geometrically.
EA NEN 7375: 2004 26

Partial covering may also be necessary for certain products with a regular and easily definable
geometric area, for example roof tiles (with edges and rounded corners) or grass tiles (with
gaps). Hollow building materials must have the holes filled with an impervious material.
Some building materials have different properties on different sides, e.g. if glazed layers or paint
are applied. In these cases, the type of material surface to be studied is isolated by covering
the other surfaces.
EA NEN 7375: 2004 27

Annex D
Assessment of a Diffusion Coefficient and Calculation of Derived Values
D.1 Assessment of the effective diffusion coefficient of a component

The effective diffusion coefficient of a component can only be calculated when, through the procedure
given in 8.3.3 and also the increment analysis in 8.3.2, it can be shown the leaching is diffusion
controlled, and when for this material the available leaching quantity is known. For this the following
procedure must be followed:
Calculate the average effective diffusion coefficient De of a component with the formula:
2
 ε 64 
De =   × f (D.1)
 2653× ρ ×U
 avail 
where:
De is the average, effective diffusion coefficient for a given component, in m2/s;

ε64 is the derived cumulative leaching of the component over 64 days determined with formula
(9), in mg/m2;
ρ is the density of the test piece, in kg dry matter per m3;
Uavail is the leachable available quantity derived according to EA NEN 7371, in mg per kg dry matter
f is a factor equal to 1 s-1.
Also express the average value of the effective diffusion coefficient in the form of a negative
logarithm:
pDe = -log De (D.2)
D.2 Assessment of a diffusion coefficient

The value of pDe indicates the rate of leaching. The minimum value of pDe (maximum rate of
leaching) for a component such as sodium is equal to 8.88 (free mobility of sodium in water).
The higher the pDe value, the lower the speed of leaching of the component concerned with constant
availability Uavail (this determines the concentration gradient which is the driving force for diffusion):
pDe > 12.5 :component with low mobility;

11.0 < pDe < 12.5 :component with average mobility;
pDe < 11.0 :component with high mobility.
A pDe value of less than 9.5 has no physical significance as the material to be studied has no further
internal porosity (tortuosity). If such a low value is found in the calculation, it is advisable to check
the availability measured.
D.3 Comparison of the mobility of a component in a moulded or monolithic material with

the free mobility of sodium in water
Tortuosity is a measurement of physical retardation and gives an indication of the path length that a
diffusing ion must cover in a porous matrix. It is a material property and therefore not ion-
dependent. For calculation of the tortuosity, a component must be selected that has no chemical
interaction with the matrix. This component will show the lowest pDe value in the matrix concerned.
In most cases, sodium is the best choice.
EA NEN 7375: 2004 28

The tortuosity of a moulded or monolithic material can be calculated using the formula:
D Na
T= (D.3)
De, Na
where:
T is the tortuosity of the material;

DNa is the diffusion coefficient of sodium in water (10-8.88) in m2/s;
De,Na is the effective diffusion coefficient of sodium in the material in m2/s.
The retention factor is an indicator of the chemical retention of a component in a moulded or

monolithic material. For a component that shows no interaction with the material matrix, this is equal
to 1.
The retention factor (R) for the component concerned can be calculated using the formula:
D
R= (D.4)
De × T
where:
R is the retention factor;

D is the diffusion coefficient for the component in water in m2/s;
De is the effective diffusion coefficient for the component in the material in m2/s;
T is the tortuosity of the material.
D.4 Determination of the leached quantity per unit mass in the diffusion test
The quantity of a component leached out per mass unit up to a time t can be calculated using the
formula:
De × t
2 × A × ρ × U avail ×
U dif ,t =
π (D.5)
m
where:
Udif,t is the quantity of a component leached out in the diffusion test to time t in mg per kg dry
matter;
Uavail is the quantity of component available for leaching in mg per kg dry matter;
De is the effective diffusion coefficient of the component in m2/s;
t is the time duration of the leaching in s;
A is the area of the test piece in m2;
ρ is the density of the test piece in kg dry matter per m3;
m is the mass of the test piece in kg dry matter.
From the leached quantities of a specific component as calculated in formula (17), and the content of
the component available in the test piece, the extent of depletion can be approximated. For this, the
relative leaching in the diffusion test must be calculated using the formula:
U dif ,t
UPdif ,t = × 100% (D.6)
U avail
where:
EA NEN 7375: 2004 29

UPdif,t is the percentage of leached component in time t of the diffusion test in relation to the
available content in the test piece
Udif,t is the leached quantity of the component in time t of the diffusion test in mg per kg dry
matter;
Uavail is the quantity of the component available for leaching in mg per kg dry matter.
EA NEN 7375: 2004 30

Annex E (informative)
Graphical representation of diffusion controlled leaching in special cases.
E.1 Diffusion Controlled Leaching
60 000
E.2 Depletion of Mobile Component
5 000 000
2
mg/m
10 000
1 000 000
Leaching
2
mg/m
100 000
1 000
Leaching
2
mg/m
300 10 000
0.1 1 10 100 0.1 1 10 100
Days Days
Time
E.3 Delayed Leaching

E.4 Surface Wash-off
50 000
30 000
2
mg/m 10 000
2
mg/m
10 000 1 000
100
Leaching
2
mg/m 10
Leaching 1
1 000 2
mg/m
500 0.1
0.1 1 10 100 0.1 1 10 100
Days Days
Time Time
E.5 Changing Release Mechanisms

E.6 Changes in Redox Conditions
100 000
50 000
2
mg/m 10 000
2
mg/m
10 000 1 000
Leaching 100
2
mg/m
1 000 10
Leaching
2
mg/m
300 1
0.1 1 10 100 0.1 1 10 100
Days Days
Time Time
KEY
Cumulative measured leaching, from 8.2.1 equation (4)
Cumulative measured leaching, from 8.2.2 equation (5)
Slope defined by rc=0.5
Upper limit defined by total content of component
Upper limit based on availability in accordance with NEN 7371
EA NEN 7375: 2004 31

Annex F
Explanation of the calculation of the upper limit for leaching in special cases
If a material behaves as a porous matrix, it may be assumed that all components evenly distributed in
the matrix basically leach diffusion controlled. Even for this type of material it is not always possible
to demonstrate for each component a diffusion controlled release using procedure 8.3.4. This occurs
mainly in components that only have a low availability and/or a high pDe value. Also other factors like
wash-off, dissolution of only the outer layer of the moulded or monolithic material, chemical
specification, complex eluate compositions etc. can lead to no diffusion coefficient being determined
for specific components.
In some cases also for components for which no diffusion coefficient could be determined according
to 8.3.4, it is possible to give an indication of the cumulative release to be expected based on the
results of the diffusion test. For 5 special cases formulas are given in 8.6 of this standard to estimate
the upper limit of leaching after a time period of 64 days and for any given time period T (>64 days),
respectively. The leaching εT after T days will always be calculated from the ε64 value using a factor
√(T/64). Partly caused by the restrictions of the one-dimensional diffusion model it can occur that the
calculated upper limit in this way is substantially larger than the available amount for the object under
investigation given by the formula:
εb = Uavail x ρ x d (F.1)
where:
εb is the calculated cumulative release of a component in the object under investigation, in mg

dry matter per m2;
Uavail is the available amount for leaching in mg/kg dry matter;
ρ is the density of the test piece in kg dry matter per m3;
d is the thickness of material under investigation in m.
If it is found that εb is smaller than εT then the value of εb should be taken as the best estimate of the
upper limit.
If a more precise insight into the level of leaching is required than an indicative upper limit, the
diffusion test must be carried out with more accurate analysis instruments, a longer test duration,
longer periods between replacement or a lower fluid-volume ratio. This standard does not give
instructions for this as the approach is not normally considered necessary.
EA NEN 7375: 2004 32


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EA NEN 7375:2004

LEACHING CHARACTERISTICS OF MOULDED OR MONOLITHIC

DETERMINATION OF LEACHING OF INORGANIC COMPONENTS

‘THE TANK TEST’

Based on a translation of the

NETHERLANDS NORMALISATION INSTITUTE STANDARD

EA NEN 7375: 2004 2

Annex A - Validation of the diffusion test.

ISO 10523:1994 Water Quality – Determination of pH

EA NEN 7371:2004 Environment Agency standard based on a translation of the Netherlands

EA NEN 7375: 2004 3

5.1 Demineralised Water

5.2 Nitric acid

6. Apparatus and Equipment

The apparatus listed under 6.5 and 6.6 must be calibrated.

EA NEN 7375: 2004 4

6.2 Filtration equipment

6.3 Membrane filters

6.4 Storage bottles

6.6 Conductivity meter

6.7 Measuring beaker or balance

7.1 Eluate samples

EA NEN 7375: 2004 5

7.2 Determination of geometric area A of the test piece

A distinction is made between:

The geometric area of test pieces in b) must be determined according to 7.2.2.

EA NEN 7375: 2004 6

1. Cover the parts of the surface:

7.2.3 Heavily irregular test pieces with no discernible regular side

7.3 Performing the diffusion test

EA NEN 7375: 2004 7

a) if no part of the surface is covered:

2 ×Vp ≤ V ≤ 5×Vp (1)

b) if parts of the surface are covered:

V is the volume of leaching fluid in litres;

Seal the tank or bucket.

EA NEN 7375: 2004 8

Period (n) Time (days)

7.4 Analysis of the eluates

S7-8 > 1.5 x Vp/V + 10^(pH7-8 – 11.78) + 10^(2.5 – pH7-8)

EA NEN 7375: 2004 9

V is the volume of leaching fluid, in l;

If criterion 1 is satisfied, continue to criterion 2.

8.1 Measured leaching of a component per fraction

E*i is the measured leaching of a component in fraction i, in mg/m2;

8.2 Measured and derived cumulative leaching of a component

8.2.1 Measured cumulative leaching

The calculation method is explained as in Figure 1 below.

8.2.2 Derived cumulative leaching of a component

Carry out this calculation as follows:

ε n = ( Ei* × ti ) /( ti − ti −1 ) for n=1 to N (where i =n) (5)

EA NEN 7375: 2004 11

Figure 1: Diagrammatic overview of terms used in this standard in determining the

8.3 Determination of the leaching mechanism(s) occurring in the diffusion test

8.3.1 Definition of incremental periods

EA NEN 7375: 2004 12

8.3.2 Incremental analysis per component

CFa-b = mean concentration in the increment (6)

EA NEN 7375: 2004 13