ETL 1110-1-158
28 Feb 95
-Has the sample expanded, shrunk, evolved gas, etc.?
-Did the temperature of the sample increase?
-Was the reaction between the waste and reagents violent?
If one or more of the initial test samples has satisfactory
physical properties, that sample is then subjected to a leaching
test. Replicate testing is often not performed during this stage
of the treatability study. Using the information gained from the
above tests, either a general S/S formulation is selected or the
initial formulation step is reiterated using different reagents
and/or mix ratios. When acceptable results have been obtained,
the next step is optimization.
(2) Mix Design Optimization. During the optimization phase
of the study, several of the most promising reagents and mix
ratios are selected and a more thorough set of tests is performed
on these mix ratios. The cure time for this phase of testing
will usually be longer than during the initial mixing phase.
Cure times are typically 3 to 28 days.
Usually chemical
leaching and several physical tests are performed on the test
samples during this phase. Replicate testing should also be
performed to provide assurance of the accuracy of the results.
The subsamples used during the initial characterization stage can
be used during this stage to create replicate samples.
h. Test Samples. Treatability study test samples must be
prepared uniformly during each phase of testing in order to allow
valid comparisons between the various mix ratios being tested.
The following paragraphs describe typical sample preparation
procedures.
(1) Sample Preparation. Many of the test methods used to
evaluate the effectiveness of the S/S process during a
treatability study do not specify sample molding requirements.
To determine the density at which samples will be tested, a
compaction test is often performed to determine maximum density
and optimum moisture content. Based on the compaction data,
samples are tested at some percentage of maximum density
(typically 90 percent). Treated material is weighed out and
compacted into molds which will produce samples with the correct
length to diameter ratio for the tests which will be performed.
In some instances pieces of the samples tested for unconfined
compressive strength have been collected and tested for
leachability.
(2) Curing Procedure. Samples are normally cured at 95-100
percent relative humidity at 20 to 25 degrees C in a temperature-
humidity controlled chamber.
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