Environmental Engineering Reference
In-Depth Information
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Performance tests, which relate to the properties of the material in use
(e.g., strength, leachability).
These categories include physical and chemical (predominantly leaching) tests,
and may be used for understanding mechanisms, assessing compliance with refer-
ence criteria (e.g., regulatory), or on-site verification, i.e., quality control in practical
field situations.
It is difficult to predict and also simulate in the laboratory the long-term envi-
ronmental conditions to which the S/S material might be subjected. For this reason,
and also because the behavior of an S/S material is complex, its performance is
generally evaluated using a combination of several physical and chemical tests. Each
test provides a partial insight into the behavior of the S/S material and hence the
effectiveness of the S/S treatment system. Several different tests may exist with the
objective of measuring the same intrinsic property; the results of these tests will
differ depending on the specific testing conditions. Therefore, consideration of the
results and their relationship to the performance criteria in light of the specific testing
conditions is essential.
The purpose of this chapter is to review current practice in test methods and
performance criteria under the broad categories of physical and chemical tests to
consider the acceptability of S/S materials for their intended management scenarios.
Some of these tests are also often carried out on the original material to be treated
to assess its suitability for S/S treatment, and also on binders to assess their effec-
tiveness. Both test methods and performance criteria are also placed in the context
of a number of international regulatory frameworks.
11.2
LEACHING TESTS
11.2.1
I
NTRODUCTION
Since the leaching characteristics of S/S materials are of the most concern, Chapter
10 discusses in detail the leaching mechanisms, factors that control constituent
leaching from cement-based materials, and leaching evaluation tests applicable to
S/S materials.
Although numerous leaching test methods have been proposed, many are variations
on the same basic principle with modifications in the specific testing conditions. A
number of systems have been developed for classifying leaching tests. The system
proposed by van der Sloot et al.
5
is based on (i) equilibrium or semi-equilibrium tests,
(ii) dynamic tests, and (iii) specific tests focusing on chemical speciation. An earlier
system
1,6,7
classifies leaching tests as either extraction tests or dynamic tests based on
whether the leachant is renewed (in the case of the latter) or not (the former). Extraction
tests include all tests that contact a specific amount of leachant with a specific amount
of material for a specific amount of time.
6
Dynamic tests include all tests that contin-
uously or intermittently renew the leachant to maintain a driving force for leaching
and generate information as a function of time while attempting to preserve the
structural integrity of the material.
6
This chapter summarizes the leaching test methods
based on the latter classification method.
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