ASTM D5744-18

Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell

SIGNIFICANCE AND USE
5.1 The laboratory weathering procedure will generate data that can be used to: (1) determine whether a solid material will produce an acidic, alkaline, or neutral effluent, (2) identify solutes in the effluent that represent dissolved weathering products formed during a specified period of time, (3) determine the mass of solute release, and (4) determine the rate at which solutes are released (from the solids into the effluent) under the closely controlled conditions of the test.  
5.2 Data generated by the laboratory weathering procedure can be used to address the following objectives: (1) determine the variation of drainage quality as a function of compositional variations (for example, iron sulfide and calcium+magnesium carbonate contents) within individual mine-rock lithologies, (2) determine the amount of acid that can be neutralized by the sample while maintaining drainage pH ≥6.0 under the conditions of the test, (3) estimate mine-rock weathering rates to aid in predicting the environmental behavior of mine rock, and (4) determine mine-rock weathering rates to aid in experimental design of site-specific kinetic tests.  
5.3 The laboratory weathering procedure provides conditions conducive to oxidation of solid material constituents and enhances the transport of weathering reaction products contained in the resulting weekly effluent. This is accomplished by controlling the exposure of the solid material sample to such environmental parameters as reaction environment temperature and application rate of water and oxygen.  
5.4 Because efficient removal of reaction products is vital to track mineral dissolution rates during the procedure, laboratory leach volumes are large per unit mass of rock to promote the rinsing of weathering reaction products from the mine-rock sample. A comparison of laboratory kinetic tests with field tests has shown that more reaction products from mineral dissolution are consistently released per unit weight and unit time in laborat...
SCOPE
1.1 This kinetic test method covers a laboratory weathering procedure that (1) enhances reaction-product transport in the aqueous leach of a solid material sample of specified mass, and (2) measures rates of weathering-product mass release. Soluble weathering products are mobilized by a fixed-volume aqueous leach that is performed and collected weekly. Leachate samples are analyzed for pH, alkalinity/acidity, specific conductance, sulfate, and other selected analytes.  
1.1.1 This test method is intended for use to meet kinetic testing regulatory requirements for mining waste rock and ores sized to pass a 6.3-mm (0.25-in.) Tyler screen.  
1.1.2 Interlaboratory testing of this method has been confined to mine waste rock. Application of this test method to metallurgical processing waste (for example, mill tailings) is outside the scope of the test method.  
1.2 This test method is a modification of a laboratory weathering procedure developed originally for mining wastes (1-3).2 However, it may have useful application wherever gaseous oxidation coupled with aqueous leaching are important mechanisms for contaminant mobility.  
1.3 This test method calls for the weekly leaching of a well-characterized solid material sample (weighing at least 1000 g) with water of specified purity, and the collection and chemical characterization of the resulting leachate. Test duration is determined by the user’s objectives of the test. See Guide D8187.3  
1.4 As described, this test method may not be suitable for some materials containing plastics, polymers, or refined metals. These materials may be resistant to traditional particle size reduction methods.  
1.5 Additionally, this test method has not been tested for applicability to organic substances and volatile matter.  
1.6 This test method is not intended to provide leachates that are identical to the actual leachate produced from a solid material in the field or to produce leach...

General Information

• Status: Published
• Publication Date: 31-Aug-2018
• ICS: 13.030.10 - Solid wastes
• ICS: 19.040 - Environmental testing
• Technical Committee: D34 - Waste Management
• Drafting Committee: D34.01.04 - Waste Leaching Techniques

Relations

• Replaces: ASTM D5744-13e1 - Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• Effective Date: 01-Sep-2018
• Refers: ASTM D2234/D2234M-19 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Dec-2019
• Refers: ASTM D75/D75M-19 - Standard Practice for Sampling Aggregates
• Effective Date: 01-Nov-2019
• Refers: ASTM D8187-18 - Standard Guide for Interpretation of Standard Humidity Cell Test Results
• Effective Date: 01-Apr-2018
• Refers: ASTM D420-18 - Standard Guide for Site Characterization for Engineering Design and Construction Purposes
• Effective Date: 01-Feb-2018
• Refers: ASTM D2234/D2234M-17 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 15-Oct-2017
• Refers: ASTM D737-04(2016) - Standard Test Method for Air Permeability of Textile Fabrics
• Effective Date: 01-Jul-2016
• Refers: ASTM D2234/D2234M-16 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Mar-2016
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D75/D75M-13 - Standard Practice for Sampling Aggregates
• Effective Date: 15-Dec-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E2242-12a - Standard Test Method for Column Percolation Extraction of Mine Rock by the Meteoric Water Mobility Procedure
• Effective Date: 01-Dec-2012
• Refers: ASTM D737-04(2012) - Standard Test Method for Air Permeability of Textile Fabrics
• Effective Date: 01-Jul-2012
• Refers: ASTM E2242-12e1 - Standard Test Method for Column Percolation Extraction of Mine Rock by the Meteoric Water Mobility Procedure
• Effective Date: 01-Jun-2012
• Refers: ASTM E2242-12 - Standard Test Method for Column Percolation Extraction of Mine Rock by the Meteoric Water Mobility Procedure
• Effective Date: 01-Jun-2012

Overview

ASTM D5744-18 is the Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell, published by ASTM International. This method is widely used in environmental and mining industries to assess the weathering behavior of mine waste rock and ore. The primary goal of this kinetic test is to simulate the laboratory weathering of solid materials under controlled conditions. The procedure enhances the transport of reaction products in aqueous leachate and quantifies the release rates of key solutes such as acidity, metals, and sulfate.

This standard provides a structured approach for regulatory compliance, environmental impact assessments, and prediction of acid rock drainage. The results obtained help determine effluent acidity/alkalinity, identify dissolved weathering products, evaluate solute mass release, and estimate solute release rates.

Key Topics

• Laboratory Weathering Procedure:
  The ASTM D5744-18 method subjects a well-characterized solid sample - typically mine waste rock sized to pass a 6.3-mm screen - to weekly fixed-volume leaching. The effluent is then analyzed for pH, acidity/alkalinity, specific conductance, sulfate, and other selected parameters.

• Controlled Testing Conditions:
  Critical test parameters include controlled air and water flow, temperature, and humidity, which promote oxidation and efficient removal of reaction products from the solid sample.

• Effluent Analysis:
  Weekly leachate collection and chemical analysis provide insights into the chemistry of released solutes-vital for understanding acid generation, neutralization, and overall environmental behavior.

• Acid-Producing and Neutralizing Potential:
  The test data can be used to establish whether a material will cause acidic, alkaline, or neutral drainage, and to quantify how much acid can be neutralized while maintaining a target pH.

• Test Limitations:
  The method is not suited for all solid materials, especially those with plastics, polymers, refined metals, organic substances, or volatile matter. It does not simulate field leachate precisely or serve as the sole basis for engineering designs.

Applications

• Mining Waste Management:
  ASTM D5744-18 is instrumental in assessing the environmental risk of mine waste rock and ore. It supports compliance with regulatory requirements regarding acid mine drainage and helps operators predict the long-term behavior of mined materials.

• Environmental Site Assessment:
  Results generated are crucial for site-specific risk analysis, reclamation planning, and remediation strategies for mining operations.

• Research and Experimental Design:
  The test assists researchers in understanding weathering kinetics, designing further kinetic tests, and refining predictions for large-scale field conditions.

• Quality Control:
  Mining companies and environmental consultants use this standard as part of their routine material characterization to ensure environmentally responsible waste management.

Related Standards

• ASTM D8187 – Guide for interpretation of standard humidity cell test results.
• ASTM D1193 – Specification for reagent water, used in the leaching process.
• ASTM E1915 – Test methods for analysis of metal-bearing ores and related materials for carbon, sulfur, and acid-base characteristics.
• ASTM D1125, D1293, D1067 – Test methods for water quality parameters such as pH, acidity/alkalinity, and conductivity.
• ASTM E2242 – Test method for column percolation extraction of mine rock by the meteoric water mobility procedure.

By adhering to ASTM D5744-18, organizations can systematically assess the potential for acid generation and contaminant mobility in solid materials, supporting better environmental stewardship and regulatory compliance across the mining sector.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5744 − 18
Standard Test Method for
Laboratory Weathering of Solid Materials Using a Humidity
Cell
This standard is issued under the fixed designation D5744; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 Additionally, this test method has not been tested for
applicability to organic substances and volatile matter.
1.1 This kinetic test method covers a laboratory weathering
procedure that (1) enhances reaction-product transport in the 1.6 This test method is not intended to provide leachates
that are identical to the actual leachate produced from a solid
aqueousleachofasolidmaterialsampleofspecifiedmass,and
(2)measuresratesofweathering-productmassrelease.Soluble material in the field or to produce leachates to be used as the
sole basis of engineering design.
weathering products are mobilized by a fixed-volume aqueous
leachthatisperformedandcollectedweekly.Leachatesamples
1.7 Thistestmethodisnotintendedtosimulatesite-specific
are analyzed for pH, alkalinity/acidity, specific conductance,
leaching conditions. It has not been demonstrated to simulate
sulfate, and other selected analytes.
actualdisposalsiteleachingconditions.Furthermore,thetestis
1.1.1 This test method is intended for use to meet kinetic
not designed to produce effluents that are in chemical equilib-
testingregulatoryrequirementsforminingwasterockandores
rium with the solid phase sample.
sized to pass a 6.3-mm (0.25-in.) Tyler screen.
1.8 This test method is intended to describe the procedure
1.1.2 Interlaboratory testing of this method has been con-
for performing the laboratory weathering of solid materials. It
fined to mine waste rock. Application of this test method to
does not describe all types of sampling and analytical require-
metallurgical processing waste (for example, mill tailings) is
ments that may be associated with its application.
outside the scope of the test method.
1.9 The values stated in SI units are to be regarded as
1.2 This test method is a modification of a laboratory
standard. No other units of measurement are included in this
weathering procedure developed originally for mining wastes
2 standard.
(1-3). However, it may have useful application wherever
1.9.1 Exception—The values given in parentheses are for
gaseousoxidationcoupledwithaqueousleachingareimportant
information only.
mechanisms for contaminant mobility.
1.10 This standard does not purport to address all of the
1.3 This test method calls for the weekly leaching of a
safety concerns, if any, associated with its use. It is the
well-characterized solid material sample (weighing at least
responsibility of the user of this standard to establish appro-
1000g) with water of specified purity, and the collection and
priate safety, health, and environmental practices and deter-
chemical characterization of the resulting leachate. Test dura-
mine the applicability of regulatory limitations prior to use.
tion is determined by the user’s objectives of the test. See
1.11 This international standard was developed in accor-
Guide D8187.
dance with internationally recognized principles on standard-
1.4 As described, this test method may not be suitable for
ization established in the Decision on Principles for the
some materials containing plastics, polymers, or refined met-
Development of International Standards, Guides and Recom-
als.Thesematerialsmayberesistanttotraditionalparticlesize
mendations issued by the World Trade Organization Technical
reduction methods.
Barriers to Trade (TBT) Committee.
2. Referenced Documents
This test method is under the jurisdiction ofASTM Committee D34 on Waste 2.1 ASTM Standards:
Management and is the direct responsibility of Subcommittee D34.01.04 on Waste
D75/D75MPractice for Sampling Aggregates
Leaching Techniques.
D276Test Methods for Identification of Fibers in Textiles
Current edition approved Sept. 1, 2018. Published October 2018. Originally
approved in 1996. Last previous edition approved in 2013 as D5744–13. DOI:
10.1520/D5744-18.
2 4
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof For referenced ASTM standards, visit the ASTM website, www.astm.org, or
this standard. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Additional published guidance sources are listed under 11.4 (Test Duration), Standardsvolume information, refer to the standard’s Document Summary page on
subparagraphs 11.4.4.1 and 11.4.4.2. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5744 − 18
D420Guide for Site Characterization for Engineering De- 3.1.5 mill tailings, n—finely ground ore processing waste
sign and Construction Purposes (commonly passing a 150-µm (100 mesh) screen) resulting
D653Terminology Relating to Soil, Rock, and Contained
from the mill processing of ore.
Fluids
3.1.6 neutralizing potential, NP, n—capacity of a solid
D737Test Method for Air Permeability of Textile Fabrics
materialsampletoneutralizeanacidiceffluentwhilemaintain-
D1067Test Methods for Acidity or Alkalinity of Water
ing a drainage pH of at least 6.0. NP is expressed in terms of
D1125Test Methods for Electrical Conductivity and Resis-
tonnes of calcium carbonate equivalent per 1000 tonnes of
tivity of Water
solid material (3).
D1193Specification for Reagent Water
3.1.6.1 Discussion—NP can be estimated using several
D1293Test Methods for pH of Water
techniques, including the following: (1) determining the
D1498Test Method for Oxidation-Reduction Potential of
amountofcalciumandmagnesiumcarbonateinthesample;(2)
Water
D2234/D2234MPractice for Collection of a Gross Sample digestingthesolidmaterialwithanexcessofstandardizedacid
of Coal and back titrating with a standardized base to measure and
D3370Practices for Sampling Water from Closed Conduits
convert the residual acid to calcium carbonate equivalents (2,
D8187Guide for Interpretation of Standard Humidity Cell
6); and (3) determining the carbonate carbon content in the
Test Results
sample (for exampleTest Methods E1915 acid-base classifica-
E276TestMethodforParticleSizeorScreenAnalysisatNo.
tion).
4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and
3.1.6.2 Discussion—The AP and NP are specifically appli-
Related Materials
cable to the determination of AP from mining wastes com-
E691Practice for Conducting an Interlaboratory Study to
prisedofironsulfideandcarbonateminerals.Thesetermsmay
Determine the Precision of a Test Method
be applicable to any solid material containing iron sulfide and
E877Practice for Sampling and Sample Preparation of Iron
carbonate minerals.
Ores and Related Materials for Determination of Chemi-
3.1.6.3 Discussion—Calciumplusmagnesiumcarbonatede-
cal Composition and Physical Properties
terminationgenerallyprovidesareasonablyaccurateNPquan-
E1915TestMethodsforAnalysisofMetalBearingOresand
tification for samples in which carbonate minerals are present.
Related Materials for Carbon, Sulfur, and Acid-Base
Digestion and back-titration techniques generally overestimate
Characteristics
the capacity of mine waste samples to neutralize acid while
E2242Test Method for Column Percolation Extraction of
maintaining drainage pH ≥6.0. These techniques can yield
Mine Rock by the Meteoric Water Mobility Procedure
negativevaluesifthereisexcesssolubleacidityonthesample.
Carbonate-carbon determinations will overestimate the capac-
3. Terminology
ity of mine-waste samples to neutralize acid if they contain
3.1 Definitions:
metal carbonate minerals that are not net neutralizing (for
3.1.1 acid-producing potential, AP, n—maximum potential
example, iron carbonates such as siderite (FeCO ) (7)).
for a solid material sample to produce acidic effluent can be
3.1.6.4 Discussion—AP and NP comprise most acid-base
determined based on the total sulfur present in the sample.
classifications and these two components have historically
3.1.1.1 Discussion—It is assumed that this sulfur is present
been determined by several different analytical methods (7).
asironsulfides(forexample,pyrite) (4).Thisassumptionleads
However, only one acid-base classification is currently an
to overestimation of the acid-producing potential of samples
ASTM standard, Test Methods E1915. Test Methods E1915
containingnon-ferroussulfidemineralssuchasgalena(PbS)or
uses either pyrolysis or chemical treatment of the mine-waste
non-acid-producing, sulfur-bearing minerals such as gypsum
sample to speciate and quantify sulfide-sulfur and carbonate-
(CaSO ). The AP is commonly converted to the amount of
carbon concentrations, which are expressed as acid-generating
calcium carbonate required to neutralize the resulting amount
potential(AGP)andacid-neutralizingpotential(ANP),respec-
of the acidic effluent produced by the oxidation of contained
tively. Through this speciation, it provides a better estimate of
ironsulfideminerals;itisexpressedastheequivalenttonnesof
calcium carbonate per 1000 tonnes of solid material (3). The acid generation than historic AP determinations in which
APis,therefore,calculatedbymultiplyingthepercentofsulfur non-ferrous and non-acid-generating sulfur minerals are pres-
containedinthematerialbyastoichiometricfactorof31.2 (5). ent (for example, galena (PbSO ) and gypsum (CaSO ),
4 4
respectively).
3.1.2 interstitial water, n—residual water remaining in the
sample pore spaces at the completion of the fixed-volume
3.1.7 run-of-mine, adj—usage in this test method refers to
weekly leach.
ore and waste rock produced by excavation (with attendant
variable particle sizes) from open pit or underground mining
3.1.3 leach, n—weekly addition of water to solid material
operations.
thatisperformedeitherdropwiseorbyfloodingforaspecified
time period.
3.1.8 waste rock, n—rock produced by excavation from
3.1.4 loading, n—mass of a chemical species, which is the open pit or underground mining operations that has an eco-
nomic mineral content less than a specified economic cutoff
product of the species concentration and the mass of the
weekly leachate collected. value for metallurgical processing.
D5744 − 18
4. Summary of Test Method environmentalparametersasreactionenvironmenttemperature
and application rate of water and oxygen.
4.1 This laboratory weathering procedure is designed to
enhancethemassreleaseofacidity/alkalinity,metals,andother
5.4 Becauseefficientremovalofreactionproductsisvitalto
pertinent analytes from a sample of solid material weighing at trackmineraldissolutionratesduringtheprocedure,laboratory
least1000g.Thisisdonebyprovidingconditionsconduciveto
leach volumes are large per unit mass of rock to promote the
sample oxidation and then leaching the sample with a fixed- rinsing of weathering reaction products from the mine-rock
volume aqueous leach. Ratio of leach volume to sample mass
sample.Acomparisonoflaboratorykinetictestswithfieldtests
is0.5:1or1:1,dependingupontheefficiencyofsamplewetting has shown that more reaction products from mineral dissolu-
and amount of effluent required for chemical analyses. The
tion are consistently released per unit weight and unit time in
weekly effluent produced is characterized for dissolved weath- laboratory weathering tests (9). For example, sulfate release
ering products. This test method is performed on each sample
ratesobservedinlaboratorytestsofmetal-minerockhavebeen
in a cylindrical cell. Multiple cells can be arranged in parallel. reported to be 3 to 8 times those for small-scale field test piles
Thisconfigurationpermitsthesimultaneoustestingofmultiple
ofDuluthComplexrock (10),andfrom2to20timesthosefor
splits of the same solid material sample, or of solid material small-scale field test piles ofArchean greenstone rock (11).A
samples each characterized by different compositions.
greater increase is anticipated when laboratory rates are com-
pared with field rates measured from operational waste-rock
4.2 Two protocol options (Options A and B) comprise the
piles.
testprocedure,andtheseoptionsdifferonlyinthewaythatthe
oxygen is supplied to samples in the individual humidity cells.
5.5 FundamentalassumptionsgoverningOptionsAandBof
Option A protocol calls for weekly cycles composed of three
the procedure:
days of dry air (less than 10% relative humidity) and three
5.5.1 Option A—An excess amount of air pumped up
days of water-saturated air (approximately 95% relative hu-
through the sample during the dry- and wet-air portions of the
midity) pumped up through the sample, followed by a leach
weekly cycle reduces the potential for oxidation reaction rates
with water on Day 7. Option B protocol differs from OptionA
being limited by low-oxygen concentrations. Weekly leaches
in that each cell is stored for six days under conditions of
with low-ionic-strength water promote the removal of leach-
controlled and relatively constant temperature and humidity,
able mineral dissolution products produced from the previous
andoxygenissuppliedtothesamplebydiffusion(andpossibly
week’s weathering cycle. The purpose of the three-day dry-air
advection) of ambient air rather than by pumping.Although a
portion of the weekly cycle is to evaporate some of the water
test duration as short as 20 weeks may be suitable for some
that remains in the pores of the sample after the weekly leach
samples, more recent research indicates that a test duration
without totally drying out the sample. Consequently, sample
well beyond 20 weeks may be required depending upon the
saturation is reduced and air flow is enhanced. During the
objectives of the test (8, 9).
dry-air portion of the cycle, the oxygen diffusion rate through
the sample may increase several orders of magnitude as
5. Significance and Use
compared to its diffusion rate under more saturated conditions
of the leach. This increase in the diffusion rate under near-
5.1 The laboratory weathering procedure will generate data
dryness conditions helps promote the oxidation of such con-
thatcanbeusedto:(1)determinewhetherasolidmaterialwill
stituents as iron sulfide. Additionally, evaporation from the
produce an acidic, alkaline, or neutral effluent, (2) identify
three days of dry air increases pore water cation/anion concen-
solutes in the effluent that represent dissolved weathering
trations and may also cause increased acidity (for example, by
products formed during a specified period of time, (3) deter-
increasing the concentration of hydrogen ion generated from
mine the mass of solute release, and (4) determine the rate at
previously oxidized iron sulfide). Increased acid generation
which solutes are released (from the solids into the effluent)
will enhance the dissolution of additional sample constituents.
under the closely controlled conditions of the test.
As evaporation continues, the remaining water may become
5.2 Data generated by the laboratory weathering procedure
oversaturated with respect to some mineral phases, conse-
can be used to address the following objectives: (1) determine
quently causing them to precipitate. Some precipitated miner-
thevariationofdrainagequalityasafunctionofcompositional
als are potential sources of acidity when re-dissolved (for
variations (for example, iron sulfide and calcium+magnesium
example, melanterite, FeSO ·7H O; and jarosite,
4 2
carbonate contents) within individual mine-rock lithologies,
K Fe (OH) (SO ) ). Compared to the three days of dry air
2 6 12 4 4
(2)determinetheamountofacidthatcanbeneutralizedbythe
where the pore-water mass decreases over time, the wet
sample while maintaining drainage pH ≥6.0 under the condi-
(saturated)-air portion of the weekly cycle helps maintain a
tionsofthetest,(3)estimatemine-rockweatheringratestoaid
relatively constant mass of pore water in the sample (12).This
in predicting the environmental behavior of mine rock, and (4)
may help promote some diffusion of weathering products (for
determine mine-rock weathering rates to aid in experimental
example, re-dissolved precipitation products) in the remaining
design of site-specific kinetic tests.
pore water without totally saturating the sample and adversely
5.3 The laboratory weathering procedure provides condi- affecting oxygen diffusion.
tions conducive to oxidation of solid material constituents and
NOTE 1—Under idealized conditions (that is, infinite dilution in air and
enhances the transport of weathering reaction products con-
water),publishedoxygendiffusionratesinairarefiveordersofmagnitude
2 –1 –5 2 –1
tainedintheresultingweeklyeffluent.Thisisaccomplishedby
greater than in water (0.178 cm s versus 2.5 × 10 cm ·s at 0 and
controlling the exposure of the solid material sample to such 25°C, respectively) (13).
D5744 − 18
5.5.2 Option B—In contrast to OptionA, Option B protocol 5.11 Notable differences have been observed between Op-
does not include dry air or wet air introduction to the humidity tion A and Option B protocols:
cells during the weekly cycle. Instead, Option B requires that 5.11.1 Water retention in the solid material sample between
temperature and relative humidity be maintained within a weeklyleachesismorevariableforOptionAthaninOptionB;
constant range by storing the cells in an environmentally for Option A, standard deviations from the mean water
controlled enclosure during the six days following the weekly retention can range from 20 to 60% of the mean value;
500- or 1000-mL leach. Consequently, oxygen is delivered to comparablevaluesforOptionBhavebeenreportedatlessthan
the cells by diffusion (and possibly advection) of ambient air, 9%(14).
rather than by pumping. Because it lacks a dry-air cycle, more 5.11.2 Greater water retention in Option B cells may favor
interstitial water is retained in the Option B sample than in the dissolution of, and consequent acid neutralization by,
Option A sample during the weekly cycle. Furthermore, the magnesium-bearing minerals; increased retention may facili-
interstitial water content for Option B is more constant than tate transport of acidic reaction products from iron-sulfide
that in Option A during the weekly dry-air cycle. In addition, minerals to magnesium-bearing minerals (14).
the interstitial water content for Option B is less variable over 5.11.3 Comparisons of sulfate mass release from the same
the course of testing than that in Option A (14). sample subjected to OptionAand Option B protocols indicate
no significant difference in sulfate concentration as a result of
5.6 This test method has been conducted on metal-mine
water-retentionvariationbetweenprotocols (14).Thissuggests
wastes to classify their tendencies to produce acidic, alkaline,
theincreasedwaterretentionofOptionBdoesnotlimitoxygen
or neutral effluent, and to measure the concentrations of
diffusion to the extent that sulfide mineral oxidation rates are
selected inorganic components leached from the waste (2, 3,
reduced (14). However, samples containing greater than 7%
14-16).
sulfur have not as yet been subjected to comparable OptionA
and Option B protocol studies.
NOTE 2—Interlaboratory testing of this method to date has been
confined to mine waste rock. The method has not been tested for
NOTE 3—Examples of products from the test include the following: (1)
applicability to metallurgical processing waste.Although the method has
effluent pH, acidity/alkalinity, and specific conductance; (2) cumulative
beenappliedbysomepractitionerstofinelygroundmetallurgicalprocess-
mass release of individual solutes; and (3) release rates for individual
ing wastes such as mill tailings, those materials were not included in the
solutes (for example, the average release of µg sulfate/g of solid material
interlaboratory testing of the method. Consequently, modifications of this
sample/week).ThedissolutiontimerequiredfordepletionofestimatedNP
method might be necessary to deal with problems associated with finely
and the subsequent duration of acid generation can be estimated using the
groundmaterials,whichwouldmakethismethodaswritteninappropriate
values generated in items (2) and (3) above (15).
for kinetic testing of finely ground materials. For kinetic testing of finely
ground materials, please refer to the biological acid production potential
6. Apparatus
method in the appendix of Test Methods E1915 or other kinetic methods
accepted by the regulatory jurisdiction.
APPARATUS OPTIONS A AND B
5.7 Thefollowingareexamplesofparametersforwhichthe
6.1 Humidity Cell—A modified column constructed of ma-
scheduled weekly, semi-monthly, or monthly collected effluent
terials suitable to the nature of the analyses to be performed
may be analyzed (see 11.5.2 for suggested effluent collection
(see Practices D3370 for guidance). Multiple humidity cells
frequency):
can be arranged in an array to accommodate the simultaneous
5.7.1 pH,Eh(oxidation/reductionpotential),andconductiv-
laboratoryweatheringof different solidmaterial types(Fig. 1).
ity(seeTestMethodsD1293,D1498,andD1125,respectively,
Two different sets of humidity cell dimensions are used to
for guidance);
accommodate particle size differences present in the solid
5.7.2 Alkalinity/acidityvalues(seeTestMethodsD1067for
material:
guidance);
6.1.1 Cells having suggested dimensions of 10.2 cm
5.7.3 Cation and anion concentrations;
(4.0in.)insidediameter(ID)by20.3cm(8.0in.)heightcanbe
5.7.4 Metals and trace metals concentrations.
used to accommodate coarse solid material samples that have
been either screened or crushed to 100% passing 6.3 mm
5.8 AnassumptionusedinthistestmethodisthatthepHof
(0.25in.).
each of the leachates reflects the progressive interaction of the
6.1.2 Cells with suggested dimensions of 20.3 cm (8.0 in.)
interstitial water with the acid-generating or acid-neutralizing
ID by 10.2 cm (4.0 in.) height can be used to accommodate
capacity, or both, of the solid material under specified labora-
solid material samples that pass a 150-µm (100 mesh) screen.
tory conditions.
NOTE 4—Some coarse solid material samples may break down into
5.9 This test method produces leachates that are amenable
finer-grained weathering products that could inhibit airflow and result in
tothedeterminationofbothmajorandminorconstituents.Itis
material being ejected from the cell during Option A’s dry-air cycle.
Consequently, use of the 20.3-cm ID cell rather than the 10.2-cm ID cell
important that precautions be taken in sample collection,
maybemoreappropriate (9).Itshouldbenotedthattherearenopublished
filtration, preservation, storage, and handling to prevent pos-
ruggedness testing results for this cell.
sible contamination of the samples or alteration of the concen-
NOTE 5—For Option A, if samples are to be tested in the 20.3-cm ID
trations of constituents through sorption or precipitation.
cell, the air-entry port to the 20.3-cm ID cell needs to be moved from
beneath the sample to just slightly above the sample so that air flow is
5.10 The leaching technique, rate of leach water addition,
directed across the sample surface rather than attempting to infiltrate the
liquid-to-solidratio,andapparatussizemaynotbesuitablefor
sample up through its bottom surface. The air-exit port is centered in the
all types of solid material. lid.
D5744 − 18
FIG. 1 Side View of 16-Cell Array (Option A)
6.1.3 For cell wall thicknesses, 0.635-cm (0.25-in.) and tubing.Thetubingfromthelidleadstotheair-exitportbubbler
0.318-cm(0.125-in.)thicknesseshavebeenusedforOptionsA described in 6.19 and 6.20. The tubing from the base drains
and B, respectively.
into a collection vessel.
6.1.4 Aperforated disk (constructed of materials suitable to
NOTE6—LidsforOptionAcanhaveanO-ringsealinstalled(machined
the nature of analyses to be performed), approximately
into the plug surface) if air leakage makes it difficult to maintain constant
0.315cm (0.125 in.) thick, with an outside diameter (OD)
airflow among individual cells. Both the O-ring seal and the air exit port
suitabletothesuggestedvesselID(6.1.1and6.1.2)iselevated
bubbler (described in 6.20) have been helpful in maintaining airflow
approximately 1.25 cm (0.5 in.) above the cell bottom to throughindividualcellsofamultiple-cellarrayduringthedry-andwet-air
portions of the weekly cycle. However, flow rates may still differ
support the solid material sample (see Fig. 1).
somewhat from cell to cell because of porosity differences between
6.1.5 For Option A, the cell lid and base are 1.27 cm
samples of differing particle size distribution.
(0.5in.) thick and machined so they each include a lip and
6.1.6 LidsforOptionBdonotrequireabarbedNPTfitting.
plug; the plug portion fits into the ID of the humidity cell
top/bottom, and the lip fits over the rim of the cell opening.A The centered hole in the Option B lid is left open to allow for
hole is drilled in the center of the lid and base and tapped to exchange of ambient air during the six-day portion of the
accommodate a barbed NPT fitting for attachment to flexible weekly cycle. A hole is drilled in the center of the base and
D5744 − 18
tapped to accommodate a barbed NPT fitting. Leachate from 6.16.2 An aeration stone (similar to aquarium aeration
the cell drains directly through this fitting into a collection equipment) or commercially available gas dispersion fritted
vessel. cylinders or disks to bubble air into the humidifier water.
6.17 Flow Meter, capable of delivering air to each humidity
NOTE 7—The cell and particle size dimensions described above are
those used commonly for assessing the potential of waste-rock samples
cell at a rate of approximately 1 to 10 L/min/cell.
associated with metal-mining operations to produce acidic effluent. A
6.18 Oil/Water Trap, 0.01 µm, for inclusion in the feed-air
“shoe box”-shaped cell design with similar dimensions is preferred by
line.
some researchers (6).
6.2 Separatory Funnel Rack, capable of holding 500-mLor
6.19 Air Exit Port Bubbler—A50-mLErlenmeyerflaskwith
1-L separatory funnels above the humidity cells. a rubber stopper containing a vent and air inlet tube (Fig. 1).
Thebubblerisconnectedtotheairexitportinthehumiditycell
6.3 Filter Media, such as a 12-oz/yd polypropylene felt
lidwithflexibletubing.Thishelpsmaintainsimilarpositiveair
characterized by 22-µm (0.009-in.) diameter filaments. The
pressure throughout all of the humidity cells.
media should be able to transmit dry air at a rate of 20 to
30cfm (see Test Methods D276 and D737 for guidance). 6.20 Flexible Tubing Quick Disconnect—Afitted,two-piece
connection placed in the middle of the air exit port flexible
NOTE8—Cautionmustbeusedintheselectionoffiltermediamaterials
tubing so that the bubbler can be disconnected from the
sincetheymayaffecttheeffluentpHandchemistryadversely.Bothpyrex
wool and quartz wool retain as much as 10 to 15 g of water per g of wool humidity cell to facilitate the measurement of air flow and
(retained water tends to re-humidify the dry-air cycle to as much as 85%
relative humidity.
relativehumidity).Additionally,pyrexwoolcausestheneutraleffluentpH
6.21 Desiccant Column, 5.1 cm (2 in.) ID by 50.8 cm
to be raised by as much as 2 pH units due to leaching of the wool (11).In
addition, pyrex (borosilicate) can contribute boron if this is a constituent (20in.) length, plastic or glass cylinder capped on both ends
of interest.
(onecapshouldberemovablefordesiccantreplacement),with
an air inlet port on the bottom and an air exit port on the top.
6.4 Two Riffle Splitters, with 0.63-cm (0.25-in.) and 2.5-cm
(1.0-in.) wide riffles, respectively; the riffle splitter is a com-
6.22 Dry Air Manifold—Acylindrical manifold constructed
monly used device for obtaining representative splits of dry,
from 2.25-in. ID schedule 40 acrylic plastic tubing, 28 in. long
free-flowing granular materials.
and fitted with 16 NPT barbed fittings. The airline exiting the
desiccant column is routed directly to the cylinder, which then
6.5 Laboratory Balance, capable of weighing to 0.1 g.
supplies dry air to each cell through an airline attached to its
6.6 Analytical Balance, capable of weighing to 1.0 mg.
correspondingNPTbarbedfitting.Thecylindricalmanifoldfits
6.7 Screen, 6.3 mm (0.25 in.).
atop the separatory funnel rack.
6.8 Screen, 150 mm (100 mesh).
OPTION B
6.9 Drying Oven—Any thermostatically controlled drying
6.23 Environmentally Controlled Enclosure—Any enclo-
oven capable of maintaining a steady temperature of 40 6
sure suitably sized to accommodate the number of samples
2°C.
being tested and associated equipment, and capable of main-
6.10 pH Meter—Any pH meter with readability of 0.01
taining consistent humidity (610 %) and temperature
units and an accuracy of 60.05 units at 25°C; two-channel
(62°C).
operation (that is, pH and Eh) is desirable.
6.23.1 Temperature Control—Any commercially available
heatercapableofmaintainingconsistenttemperaturewithinthe
6.11 Conductivity Meter, capable of reading in micromhos
enclosure.
(microseimens); calibrate at 25°C.
6.23.2 Humidity Control—Any commercially available hu-
6.12 Separatory Funnel, 500 mL or 1 L, one per each
midifier and dehumidifier capable of maintaining consistent
humidity cell.
humidity within the enclosure.
6.13 Collection Vessel, vessel such as an Erlenmeyer flask
6.23.3 Instruments to Measure Temperature and Humidity—
or Nalgene bottle, 500 mL or 1 L, one per each humidity cell.
Any commercially available manual or digital hygrometer/
thermometer (see 6.15). Temperature should be readable to at
6.14 Volumetric Flask, 500 mL or 1 L.
least 1°C and relative humidity to 1%.
OPTION A
6.23.4 Fan—Any commercially available fan to provide air
circulation within the enclosure.
6.15 Digital Hygrometer/Thermometer, with a relative hu-
midity range of 5 to 95%, and temperature range of –40 to
7. Reagents
104°C (–40 to 220°F).
7.1 Purity of Reagents—Reagent-grade chemicals shall be
6.16 Cylindrical Humidifier, with suggested dimensions of
used in all tests. Unless otherwise indicated, it is intended that
12.1 cm (4.75 in.) ID by 134.6 cm (53.0 in.) length. The
all reagents conform to the specifications of the Committee on
following associated equipment are needed to provide satu-
rated air for the three-day wet-air portion of the weekly cycle:
6.16.1 A thermostatically controlled heating element to
maintain the water temperature at 25°C during the wet-air
The tolerance ranges for humidity and temperature are the range of differences
cycle. of maximum and minimum values from the mean of the respective data.
D5744 − 18
Analytical Reagents of theAmerican Chemical Society, where generation of excessive fines can be limited by stage crushing
such specifications are available. theoversizematerialinthreesteps: (1)large-jawcrushersetat
1.92 cm, (2) small-jaw crusher set at 0.95 cm, and (3) roll
7.2 Purity of Water—Unless otherwise indicated, references
crusher set at 0.64 cm. After each of the first two crushing
to water shall be understood to mean reagent water as defined
steps, the –0.64-cm fraction is collected and the oversize is
by Type III at 18 to 27°C conforming to Specification D1193.
passed to the next crushing phase.
Themethodbywhichthewaterisprepared,thatis,distillation,
9.2.1 Caution—Crushing a bulk sample so it passes a
ion exchange, reverse osmosis, electrodialysis, or a combina-
6.3-mm (0.25-in.) screen may change the character of the
tion thereof, should remain constant throughout testing.
sample by artificially increasing liberation and consequent
7.3 Purity of Air—The feed air line shall contain a 0.01-µm
surface areas of acid-producing and acid-consuming minerals
oil/water trap in advance of the flow meter.
contained in the +6.3-mm (0.25-in.) material.Asuggestion for
avoiding this problem is to segregate the −6.3-mm (0.25-in.)
8. Sampling
fraction by screening rather than crushing, and to test that
8.1 Collect the samples to be tested using available sample
fraction according to the protocol and equipment described in
methods developed for the specific industry (see Practices
thistestmethod.The+6.3-mm(0.25-in.)materialcaneitherbe
D75/D75M and E877, Guide D420, Terminology D653, and
stage crushed (as in 9.2), or tested separately. For example,
Practice D2234/D2234M).
column testing could be conducted, although no standard
protocolhasbeenestablishedforthistesting.Samplesfromthe
8.2 The sampling methodology for materials of similar
drill core and cuttings also present material sizing problems,
physical form shall be used where no specific methods are
which must be considered when interpreting drill core and
available.
cuttings laboratory weathering data. The drill core must be
8.3 The amount of material recommended to be sent to the
crushed to −6.3-mm (0.25-in.) to fit the cell described in this
laboratory should be sufficient to provide 8 to 10 kg of bulk
test method. The resulting size distribution from crushing will
sample for splitting, analysis, and testing (see 9.3).
differ from that of run-of-mine due to differences in fracture
NOTE 9—Additional information on theory and methods for obtaining
patternsinherenttoblastingpracticesthatproducerun-of-mine
representative samples are contained in Pitard (16).
material. By contrast, drill cuttings size fractions are com-
8.4 To prevent sample contamination or constituent loss
monly less than 6.3 mm (0.25 in.) due to the rotary-percussive
prior to testing, store the samples in closed containers that are nature of obtaining the sample. The effects of particle size
appropriatetothesampletypeanddesiredanalyses(seeGuide
distribution changes resulting from the more finely crushed
D420 for guidance). sampleorfromrotarydrillcuttingsshouldbeconsideredinthe
interpretation of data. In particular, particle size reduction will
8.5 The time elapsed between sample collection and subse-
increase specific surface area of acid-generating and acid-
quent humidity cell testing should be minimized to reduce the
neutralizing minerals and is likely to increase liberation of
amount of sample pre-oxidation (see Practices D3370 for
these minerals. Both of these effects will tend to increase the
guidance).Reportthelengthoftimebetweensamplecollection
surface area of these minerals available for reaction. If this
and testing.
increase is biased towards either acid-generating or acid-
neutralizing minerals, the balance of acid-generating and
9. Sample Preparation
acid-neutralizing reactions will shift.
9.1 Air dry as-received bulk samples of solid material to
9.3 Mix and divide the bulk sample to obtain a representa-
prevent the additional oxidation of reactive minerals or com-
pounds. If air drying is not practicable, oven dry the solid tive test unit with a weight in the range of 8 to 10 kg, using a
riffle splitter with 1-in. (2.54-cm) chutes (perform in accor-
material at a maximum temperature of 40°C for 24 h, or until
a constant weight is reached. dance with Practice E877, Sampling and Preparation
Procedure-Riffling). Divide the test unit into eight nominal
NOTE 10—Oven drying at temperatures above 40°C may introduce
1-kg test specimens. Store each test specimen in a resealable
chemical and physical changes in certain mineral species comprising the
plastic bag. (To prevent continued atmospheric oxidation of
sample (9).Thesepotentialchangesshouldbeevaluatedandaccountedfor
in the analysis of the test data.
sulfide mineral-bearing samples, samples could be vacuum
sealed or refrigerated.)
9.2 After reserving any coarse material needed for Test
Method E2242-02 (Meteoric Water Mobility Procedure) or
NOTE 11—The dried sample should be mixed through the riffle splitter
other possible testing and analyses, screen the air-dried bulk
atleastoncebeforemakinganysplits;recombinethesplitsresultingfrom
the sample mixing exercise by pouring individual splits either over each
samplesthrougha6.3-mm(0.25-in.)screeninaccordancewith
otherorthroughthesplitteragain.Oncetheactualsplitismade,itiswise
Test Method E276. Crush any oversize material so that 100%
to re-mix it (according to the above procedure) prior to making the next
passes the screen. For particles finer than 15.2 cm (6 in.), the
split. Mixing the sample through the riffle splitter may still result in
segregation of the sample. If segregation persists, use of a rotary sample
divider is advised.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, D.C. For suggestions on the testing of reagents not
9.4 Head Sample Analysis—Select one 1-kg test specimen
listed by the American Chemical Society, see Analar Standards for Laboratory
at random, and crush the dried test specimen so that at least
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
95% passes a 1.7-mm (10 mesh) screen, in accordance with
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. Test Method E276.
D5744 − 18
provide sufficient effluent to meet analytical needs, a 2-kg test specimen
9.4.1 Divide the crushed test specimen in half twice, using
could be used as long as the 0.5:1 or 1:1 leach-volume to sample-mass
a riffle splitter with 6.35-mm (0.25-in.) chutes (in accordance
ratio is maintained. Split the sample between two cells. Record and then
with Practice E877, Sampling and Preparation Procedure-
combine recovered volumes of the weekly effluent from both cells. Also
Riffling), and select a 250-g subsample at random for head
record the combined volume.
sample analysis.
9.8 Reserve the remaining test specimens for replicated
9.4.2 Transfer the selected 250-g subsample to a ring and
testing or to resolve disputed results (recommend sample
puck grinding mill and grind to a nominal 95% passing a
preservation by vacuum seal or refrigerated storage).
150-µm (100 mesh) screen, in accordance with Test Method
E276. Use the pulverized subsample to perform the following
10. Apparatus Assembly
determinations: (1) total sulfur, sulfide, and carbonate analyses
in accordance with Test Methods E1915,(2) whole-rock and
10.1 Option A—The humidity cells are table mounted at a
trace-element chemistry analyses, and (3) mineral character-
height sufficient to accommodate the placement of both the
ization to identify and quantify the different mineral species
humidifier and one collection flask for effluent collection from
comprising the sample.
thebottomofeachcell(Fig.1).Duringthewater-saturatedand
dry-airportionsofeachweeklycycle,feedairismeteredtothe
NOTE 12—Because accurate estimation of a sample’s capacity to
neutralizeacid(NP)requiresidentificationofcarbonatemineralspeciation bottomofeachcell(ormidwayupthesideincellsdesignedfor
(that is, calcite, dolomite, ferroan dolomite, siderite, and so forth), and
minus 100 mesh material) at the selected rate (1 to 10 L/min).
quantificationofcalciumandmagnesiumcontentiniron-bearingminerals
Feedairforthethree-daydry-airportionisroutedfirstthrough
(that is, ankerite, ferroan dolomite, and siderite, and so forth), these
a desiccant column and then to each of the cells through a
determinations are strongly recommended. It is also recommended that
sample whole-rock chemistry and mineralogy be compared to ensure that dry-air manifold (Fig. 2, Fig. 3). Feed air for the water-
chemistry is consistent with mineralogy and vice versa. Additionally,
saturated air portion is routed through a water-filled humidifier
leach extraction testing of the pre-test sample, compared with leach
by means of aeration stones or gas dispersion fritted cylinders/
extractiontestingofpost-testsample,maybebeneficialindeterminingthe
disks, and then to each humidity cell (Fig. 2). If necessary, a
extent of solutes released by mineral dissolution and subsequently
water-bubbling vessel can be attached to the air exit port of
sequestered in secondary solid phases during testing (17).
each humidity cell lid to maintain constant airflow among the
9.5 Screen-Fraction Analysis—Select one 1-kg test speci-
individual cells (Fig. 1).
men at random, and determine the particle size distribution in
accordance with Test Method E276. Sieve openings of 6, 10,
10.2 Option B—Thehumiditycellsaremountedonarackof
28, 35, 48, 100, 200, and 270 Tyler mesh are suggested. sufficient height to accommodate placement of vessels for
collection of effluent from the bottom of each cell. The upper
9.6 The following analyses are recommended:
portion of the rack doubles as a separatory funnel rack, and is
9.6.1 Determine the total sulfur, sulfide, and carbonate
of sufficient height to accommodate placement of the funnel
contents of individual size fractions in accordance with Test
spigot above the humidity cell lid. A simple rack of wood
Methods E1915. Whole-rock or trace-element chemical
construction is shown in Fig. 4. Note that holes are drilled in
analysis, or both, may also be performed on these fractions.
the humidity cell shelf to accommodate the barbed fitting
9.6.2 Determine the extent of acid-generating (for example,
(drain) that is centered at the bottom of each cell. Unlike the
iron sulfide, iron sulfate) and acid-neutralizing (for example,
OptionAapparatus,noairplumbingisrequired.UnlikeOption
calciumcarbonate,magnesiumcarbonate)mineralliberationof
A, Option B cells are stored in an enclosure in which
the individual size fractions.
temperature and humidity are controlled during the 6 days
NOTE13—Paragraphs9.6.1and9.6.2arerecommendedasbestpractice
following the leach. Shelves for cell storage and space for
to quantify the amount of sulfide and carbonate minerals present in each
temperature- and humidity-control equipment are required in
fractionandtheirdegreeofliberationwithinthesefractions.Theobjective
the enclosure.
oftheanalysesdescribedin9.6.1and9.6.2istoaidtheuserincorrelating
drainagequalitywithsolid-phasecompositionbyprovidingmoredetailed
10.3 Options A and B—Aseparatoryfunnelrackismounted
description of the exposed surface areas of acid-producing and acid-
on the table that holds the cells if the weekly water leach is
neutralizing minerals.These surface areas strongly affect the rates of acid
applieddropwise(dripleach).Multipleseparatoryfunnels(one
production and neutralization. With regard to the applications of testing
presented in 5.1 and 5.2, the analyses described will help to: (1) identify
for each cell) are held in the rack during the drip leach that is
whether the material being tested will produce acidic, alkaline, or neutral
performed on the seventh day of each weekly cycle (Fig. 2,
effluent; (2) determine the variation of drainage quality as a function of
Fig.4).Theseparatoryfunnelcanbeusedtometertherequired
solid-phase composition; (3) measure the amount of estimated NP
water volume slowly down the sides of the cell wall until the
accessible in the solid; and (4) in general, aid in predicting the environ-
sample is flooded if the weekly leach is to be a flooded leach.
mental behavior of the solid (see Refs (8, 18, 19)). To perform all of the
determinations described in 9.6.1 and 9.6.2, a larger mass of sample
material may be required than the stated 1 kg (18).
11. Procedure
9.7 Select one 1-kg test specimen at random for use in the
OPTIONS A AND B
laboratory weathering test method. Divide the test specimen
into four nominal 250-g subsamples using the riffle splitter
11.1 Cell Loading:
with 25.4-mm (1-in.) chutes, and label and store in resealable
11.1.1 If more than one humidity cell is used at one time,
plastic bags until it is time to load the humidity cells.
label each with a sequential number, and use the same number
NOTE 14—If the leach volume from the 1-kg sample mass does not for the matching collection vessel.
D5744 − 18
FIG. 2 Front View of 16-Cell Array (Option A) with Separatory Funnel Rack
thedrainagepHvaluesfortheendofrateperiodswerewithin0.2unitsof
11.1.2 Weigh each humidity cell (without its lid) and each
the mean, and sulfate release rates were consistently within 10% of the
collection vessel; record the tare weights of each to the nearest
mean. Consequently, because there was little difference between results
0.1 g.
from the two leach alternatives, and to simplify the method protocol, the
11.1.3 Cutthefiltermedia(suchas12-oz/yd polypropylene
flood-leach alternative is designated as the preferred water-lea
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D5744 − 13 D5744 − 18
Standard Test Method for
Laboratory Weathering of Solid Materials Using a Humidity
Cell
This standard is issued under the fixed designation D5744; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorially updated Research Report footnote information in Section 13 in December 2013.
1. Scope
1.1 This kinetic test method covers a laboratory weathering procedure that (1) enhances reaction-product transport in the
aqueous leach of a solid material sample of specified mass, and (2) measures rates of weathering-product mass release. Soluble
weathering products are mobilized by a fixed-volume aqueous leach that is performed and collected weekly. Leachate samples are
analyzed for pH, alkalinity/acidity, specific conductance, sulfate, and other selected analytes.
1.1.1 This test method is intended for use to meet kinetic testing regulatory requirements for mining waste rock and ores sized
to pass a 6.3-mm (0.25-in.) Tyler screen.
1.1.2 Interlaboratory testing of this method has been confined to mine waste rock. Application of this test method to
metallurgical-processing metallurgical processing waste (for example, mill tailings) is outside the scope of the test method.
1.2 This test method is a modification of a laboratory weathering procedure developed originally for mining wastes (1-3).
However, it may have useful application wherever gaseous oxidation coupled with aqueous leaching are important mechanisms
for contaminant mobility.
1.3 This test method calls for the weekly leaching of a well-characterized solid material sample (weighing at least
1000-g),1000 g) with water of specified purity, and the collection and chemical characterization of the resulting leachate. Test
duration is determined by the user’s objectives of the test. See Guide D8187.
1.4 As described, this test method may not be suitable for some materials containing plastics, polymers, or refined metals. These
materials may be resistant to traditional particle size reduction methods.
1.5 Additionally, this test method has not been tested for applicability to organic substances and volatile matter.
1.6 This test method is not intended to provide leachates that are identical to the actual leachate produced from a solid material
in the field or to produce leachates to be used as the sole basis of engineering design.
1.7 This test method is not intended to simulate site-specific leaching conditions. It has not been demonstrated to simulate actual
disposal site leaching conditions. Furthermore, the test is not designed to produce effluents that are in chemical equilibrium with
the solid phase sample.
1.8 This test method is intended to describe the procedure for performing the laboratory weathering of solid materials. It does
not describe all types of sampling and analytical requirements that may be associated with its application.
1.9 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9.1 Exception—The values given in parentheses are for information only.
1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.11 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee D34 on Waste Management and is the direct responsibility of Subcommittee D34.01.04 on Waste Leaching
Techniques.
Current edition approved Sept. 1, 2013Sept. 1, 2018. Published September 2013October 2018. Originally approved in 1996. Last previous edition approved in 20122013
as D5744D5744 – 13.-12. DOI: 10.1520/D5744-13E01.10.1520/D5744-18.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Additional published guidance sources are listed under 11.4 (Test Duration), subparagraphs 11.4.4.1 and 11.4.4.2.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5744 − 18
2. Referenced Documents
2.1 ASTM Standards:
D75D75/D75M Practice for Sampling Aggregates
D276 Test Methods for Identification of Fibers in Textiles
D420 Guide for Site Characterization for Engineering Design and Construction Purposes
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D737 Test Method for Air Permeability of Textile Fabrics
D1067 Test Methods for Acidity or Alkalinity of Water
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
D1193 Specification for Reagent Water
D1293 Test Methods for pH of Water
D1498 Test Method for Oxidation-Reduction Potential of Water
D2234/D2234M Practice for Collection of a Gross Sample of Coal
D3370 Practices for Sampling Water from Closed Conduits
D8187 Guide for Interpretation of Standard Humidity Cell Test Results
E276 Test Method for Particle Size or Screen Analysis at No. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and Related
Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E877 Practice for Sampling and Sample Preparation of Iron Ores and Related Materials for Determination of Chemical
Composition and Physical Properties
E1915 Test Methods for Analysis of Metal Bearing Ores and Related Materials for Carbon, Sulfur, and Acid-Base Characteristics
E2242 Test Method for Column Percolation Extraction of Mine Rock by the Meteoric Water Mobility Procedure
D5744 Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions:
3.1.1 acid-producing potential, AP, n—maximum potential for a solid material sample to produce acidic effluent can be
determined based on the total sulfur present in the sample.
3.1.1.1 Discussion—
It is assumed that this sulfur is present as iron sulfides (for example, pyrite) (4). This assumption leads to overestimation of the
acid-producing potential of samples containing non-ferrous sulfide minerals such as galena (PbS) or non-acid-producingnon-acid-
producing, sulfur-bearing minerals such as gypsum (CaSO ). The AP is commonly converted to the amount of calcium carbonate
required to neutralize the resulting amount of the acidic effluent produced by the oxidation of contained iron sulfide
minterals;minerals; it is expressed as the equivalent tonnes of calcium carbonate per 1000 tonnes of solid material (3). The AP is,
therefore, calculated by multiplying the percent of sulfur contained in the material by a stoichiometric factor of 31.2 (5).
3.1.2 interstitial water, n—residual water remaining in the sample pore spaces at the completion of the fixed-volume weekly
leach.
3.1.3 leach, n—weekly addition of water to solid material that is performed either dropwise or by flooding for a specified time
period.
3.1.4 loading, n—mass of a chemical species, which is the product of the species concentration and the mass of the weekly
leachate collected.
3.1.5 mill tailings, n—finely ground ore processing waste (commonly passing a 150-μm [100-mesh screen]) (100 mesh) screen)
resulting from the mill processing of ore.
3.1.6 neutralizing potential, NP, n—capacity of a solid material sample to neutralize an acidic effluent while maintaining a
drainage pH of at least 6.0. NP is expressed in terms of tonnes of calcium carbonate equivalent per 1000 tonnes of solid material
(3).
3.1.6.1 Discussion—
NP can be estimated using several techniques, including the followingfollowing: (1) determining the amount of calcium and
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standardsvolume information, refer to the standard’s Document Summary page on the ASTM website.
D5744 − 18
magnesium carbonate in the sample; (2) digesting the solid material with an excess of standardized acid and back titrating with
a standardized base to measure and convert the residual acid to calcium carbonate equivalents (2, 6); and (3) determining the
carbonate carbon content in the sample (for example Test MethodMethods E1915 acid base acid-base classification).
3.1.6.2 Discussion—
The AP and NP are specifically applicable to the determination of AP from mining wastes comprised of iron-sulfide iron sulfide
and carbonate minerals. These terms may be applicable to any solid material containing iron-sulfide iron sulfide and carbonate
minerals.
3.1.6.3 Discussion—
Calcium plus magnesium carbonate determination generally provides a reasonably accurate NP quantification for samples in which
carbonate minerals are present. Digestion and back-titration techniques generally overestimate the capacity of mine waste samples
to neutralize acid while maintaining drainage pH ≥ 6.0. ≥6.0. These techniques can yield negative values if there is excess soluble
acidity on the sample. Carbonate-carbon determinations will overestimate the capacity of mine-waste samples to neutralize acid
if they contain metal carbonate minerals that are not net neutralizing (for example, iron carbonates such as siderite [FeCO(FeCO ])
(7).)).
3.1.6.4 Discussion—
AP and NP comprise most acid-base classifications and these two components have historically been determined by several
different analytical methods (7). However, only one acid-base classification is currently an ASTM standard, Test MethodMethods
E1915. Test MethodMethods E1915 uses either pyrolysis or chemical treatment of the mine-waste sample to speciate and quantify
sulfide-sulfur and carbonate-carbon concentrations, which are expressed as acid-generating potential (AGP) and acid neutralizing
acid-neutralizing potential (ANP), respectively. Through this speciation, it provides a better estimate of acid generation than
historic AP determinations in which non-ferrous and non-acid-generating sulfur minerals are present (for example, galena
[PbSO(PbSO ]) and gypsum [CaSO(CaSO ], respectively.), respectively).
4 4
3.1.7 run-of-mine, adj—usage in this test method refers to ore and waste rock produced by excavation (with attendant variable
particle sizes) from open pit or underground mining operations.
3.1.8 waste rock, n—rock produced by excavation from open pit or underground mining operations that has an economic
mineral content less than a specified economic cutoff value for metallurgical processing.
4. Summary of Test Method
4.1 This laboratory-weathering laboratory weathering procedure is designed to enhance the mass release of acidity/alkalinity,
metals, and other pertinent analytes from a sample of solid material weighing at least 1000 g. This is done by providing conditions
conducive to sample oxidation and then leaching the sample with a fixed-volume aqueous leach. Ratio of leach volume to sample
mass is 0.5 : 1 or 1 : 1 0.5:1 or 1:1, depending upon the efficiency of sample wetting and amount of effluent required for chemical
analyses. The weekly effluent produced is characterized for dissolved weathering products. This test method is performed on each
sample in a cylindrical cell. Multiple cells can be arranged in parallel. This configuration permits the simultaneous testing of
multiple splits of the same solid material sample, or of solid material samples each characterized by different compositions.
4.2 Two protocol options (Options A and B) comprise the test procedure, and these options differ only in the way that the oxygen
is supplied to samples in the individual humidity cells. Option A protocol calls for weekly cycles composed of three days of dry
air (less than 10 % relative humidity) and three days of water-saturated air (approximately 95 % relative humidity) pumped up
through the sample, followed by a leach with water on Day 7. Option B protocol differs from Option A in that each cell is stored
for six days under conditions of controlled and relatively constant temperature and humidity, and oxygen is supplied to the sample
by diffusion (and possibly advection) of ambient air rather than by pumping. Although a test duration as short as 20 weeks may
be suitable for some samples, more recent research indicates that a test duration well beyond 20 weeks may be required depending
upon the objectives of the test (8, 9).
5. Significance and Use
5.1 The laboratory weathering procedure will generate data that can be used to: (1) determine whether a solid material will
produce an acidic, alkaline, or neutral effluent, (2) identify solutes in the effluent that represent dissolved weathering products
formed during a specified period of time, (3) determine the mass of solute release, and (4) determine the rate at which solutes are
released (from the solids into the effluent) under the closely controlled conditions of the test.
5.2 Data generated by the laboratory weathering procedure can be used to address the following objectives: (1) determine the
variation of drainage quality as a function of compositional variations (for example, iron sulfide and calcium+magnesium
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carbonate contents) within individual mine-rock lithologies, (2) determine the amount of acid that can be neutralized by the sample
while maintaining drainage pH ≥ 6.0 ≥6.0 under the conditions of the test, (3) estimate mine-rock weathering rates to aid in
predicting the environmental behavior of mine rock, and (4) determine mine-rock weathering rates to aid in experimental design
of site-specific kinetic tests.
5.3 The laboratory-weathering laboratory weathering procedure provides conditions conducive to oxidation of solid material
constituents and enhances the transport of weathering reaction products contained in the resulting weekly effluent. This is
accomplished by controlling the exposure of the solid material sample to such environmental parameters as reaction environment
temperature and application rate of water and oxygen.
5.4 Because efficient removal of reaction products is vital to track mineral dissolution rates during the procedure, laboratory
leach volumes are large per unit mass of rock to promote the rinsing of weathering-reaction weathering reaction products from the
mine-rock sample. A comparison of laboratory kinetic tests with field tests has shown that more reaction products from mineral
dissolution are consistently released per unit weight and unit time in laboratory weathering tests (9). For example, sulfate release
rates observed in laboratory tests of metal-mine rock have been reported to be 3 to 8 times those for small-scale field test piles
of Duluth Complex rock (10), and from 2 to 20 times those for small-scale field test piles of Archean greenstone rock (11). A
greater increase is anticipated when laboratory rates are compared with field rates measured from operational waste-rock piles.
5.5 Fundamental assumptions governing Options A and B of the procedure:
5.5.1 Option A—An excess amount of air pumped up through the sample during the dry- and wet-air portions of the weekly
cycle reduces the potential for oxidation reaction rates being limited by low-oxygen concentrations. Weekly leaches with low ionic
strength low-ionic-strength water promote the removal of leachable mineral dissolution products produced from the previous
week’s weathering cycle. The purpose of the three-day dry-air portion of the weekly cycle is to evaporate some of the water that
remains in the pores of the sample after the weekly leach without totally drying out the sample. Consequently, sample saturation
is reduced and air flow is enhanced. During the dry-air portion of the cycle, the oxygen diffusion rate through the sample may
increase several orders of magnitude as compared to its diffusion rate under more saturated conditions of the leach. This increase
in the diffusion rate under near-dryness conditions helps promote the oxidation of such constituents as iron sulfide. Additionally,
evaporation from the three days of dry air increases pore water cation/anion concentrations and may also cause increased acidity
(for example, by increasing the concentration of hydrogen ion generated from previously oxidized iron sulfide). Increased acid
generation will enhance the dissolution of additional sample constituents. As evaporation continues, the remaining water may
become over-saturatedoversaturated with respect to some mineral phases, consequently causing them to precipitate. Some
precipitated minerals are potential sources of acidity when re-dissolved (for example, melanterite, FeSO ·7H O; and jarosite,
4 2
K Fe (OH) (SO ) ). Compared to the three days of dry air where the pore-water mass decreases over time, the wet (saturated)-air
2 6 12 4 4
portion of the weekly cycle helps maintain a relatively constant mass of pore water in the sample (12). This may help promote
some diffusion of weathering products (for example, re-dissolved precipitation products) in the remaining pore water without
totally saturating the sample and adversely affecting oxygen diffusion.
NOTE 1—Under idealized conditions (that is, infinite dilution in air and water), published oxygen diffusion rates in air are five orders of magnitude
2 -1–1 -5–5 2 -1–1
greater than in water (0.178 cm s versus 2.5 × 10 cm · s·s at 0 and 25°C,25 °C, respectively) (13).
5.5.2 Option B—In contrast to Option A, Option B protocol does not include dry air or wet air introduction to the humidity cells
during the weekly cycle. Instead, Option B requires that temperature and relative humidity be maintained within a constant range
by storing the cells in an environmentally controlled enclosure during the 6six days following the weekly 500- or 1000-mL leach.
Consequently, oxygen is delivered to the cells by diffusion (and possibly advection) of ambient air, rather than by pumping.
Because it lacks a dry-air cycle, more interstitial water is retained in the Option B sample than in the Option A sample during the
weekly cycle. Furthermore, the interstitial water content for Option B is more constant than that in Option A during the weekly
dry-air cycle. In addition, the interstitial water content for Option B is less variable over the course of testing than that in Option
A (14).
5.6 This test method has been conducted on metal-mine wastes to classify their tendencies to produce acidic, alkaline, or neutral
effluent, and to measure the concentrations of selected inorganic components leached from the waste (2-, 3, 14-16).
NOTE 2—Interlaboratory testing of this method to date has been confined to mine waste rock. The method has not been tested for applicability to
metallurgical-processing metallurgical processing waste. Although the method has been applied by some practitioners to finely ground metallurgical-
processing metallurgical processing wastes such as mill tailings, those materials were not included in the interlaboratory testing of the method.
Consequently, modifications of this method might be necessary to deal with problems associated with finely ground materials, which would make this
method as written,written inappropriate for kinetic testing of finely ground materials. For kinetic testing of finely ground materials, please refer to the
biological acid production potential method in the appendix of Test Methods E1915 or other kinetic methods accepted by the regulatory jurisdiction.
5.7 The following are examples of parameters for which the scheduled weekly, semi-monthly, or monthly collected effluent may
be analyzed (see 11.5.2 for suggested effluent collection frequency):
5.7.1 pH, Eh (oxidation/reduction potential), and conductivity (see Test Methods D1293, Practice D1498, and Test Methods
D1125, respectively, for guidance);
5.7.2 Alkalinity/acidity values (see Test Methods D1067 for guidance);
5.7.3 Cation and anion concentrations;
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5.7.4 Metals and trace metals concentrations.
5.8 An assumption used in this test method is that the pH of each of the leachates reflects the progressive interaction of the
interstitial water with the acid-generating or acid-neutralizing capacity, or both, of the solid material under specified laboratory
conditions.
5.9 This test method produces leachates that are amenable to the determination of both major and minor constituents. It is
important that precautions be taken in sample collection, filtration, preservation, storage, and handling to prevent possible
contamination of the samples or alteration of the concentrations of constituents through sorption or precipitation.
5.10 The leaching technique, rate of leach water addition, liquid-to-solid ratio, and apparatus size may not be suitable for all
types of solid material.
5.11 Notable differences have been observed between Option A and Option B protocols:
5.11.1 Water retention in the solid-material solid material sample between weekly leaches is more variable for Option A than
in Option B; for Option A, standard deviations from the mean water retention can range from 20 to 60 % of the mean value;
comparable values for Option B have been reported at less than 9 % (14).
5.11.2 Greater water retention in Option B cells may favor dissolution of, and consequent acid neutralization by,
magnesium-bearing minerals; increased retention may facilitate transport of acidic reaction products from iron-sulfide minerals to
magnesium-bearing minerals (14).
5.11.3 Comparisons of sulfate mass release from the same sample subjected to Option A and Option B protocols indicate no
significant difference in sulfate concentration as a result of water-retention variation between protocols (14). This suggests the
increased water retention of Option B does not limit oxygen diffusion to the extent that sulfide mineral oxidation rates are reduced
(14). However, samples containing greater than 7 % sulfur have not as yet been subjected to comparable Option A and Option B
protocol studies.
NOTE 3—Examples of products from the test include the following: (1) effluent pH, acidity/alkalinity, and specific conductance; (2) cumulative mass
release of individual solutes; and (3) release rates for individual solutes (for example, the average release of μg sulfate/g of solid material sample/week).
The dissolution time required for depletion of estimated NP and the subsequent duration of acid generation can be estimated using the values generated
in items (2) and (3) above (15).
6. Apparatus
OPTIONS A AND B
APPARATUS OPTIONS A AND B
6.1 Humidity Cell—A modified column constructed of materials suitable to the nature of the analyses to be performed (see
Practices D3370 for guidance). Multiple humidity cells can be arranged in an array to accommodate the simultaneous laboratory
weathering of different solid material types (Fig. 1). Two different sets of humidity cell dimensions are used to accommodate
particle size differences present in the solid material:
6.1.1 Cells having suggested dimensions of 10.2-cm (4.0-in.) 10.2 cm (4.0 in.) inside diameter (ID) by 20.3-cm (8.0-in.) 20.3
cm (8.0 in.) height can be used to accommodate coarse solid material samples that have been either screened or crushed to 100 %
passing 6.3 mm (0.25 in.).(0.25 in.).
6.1.2 Cells with suggested dimensions of 20.3-cm (8.0-in.) ID by 10.2-cm (4.0-in.) 20.3 cm (8.0 in.) ID by 10.2 cm (4.0 in.)
height can be used to accommodate solid material samples that pass a 150-μm (100-mesh) (100 mesh) screen.
NOTE 4—Some coarse solid material samples may break down into finer-grained weathering products that could inhibit airflow and result in material
being ejected from the cell during Option A’s dry-air cycle. Consequently, use of the 20.3-cm ID cell rather than the 10.2-cm ID cell may be more
appropriate (9). It should be noted that there are no published ruggedness testing results for this cell.
NOTE 5—For Option A, if samples are to be tested in the 20.3-cm ID cell, the air-entry port to the 20.3 cm 20.3-cm ID cell needs to be moved from
beneath the sample to just slightly above the sample so that air flow is directed across the sample surface rather than attempting to infiltrate the sample
up through its bottom surface. The air-exit port is centered in the lid.
6.1.3 For cell wall thicknesses, 0.635-cm (0.25-in.) and 0.318-cm (0.125-in) cm thickness (0.125-in.) thicknesses have been
used for Options A and B, respectively.
6.1.4 A perforated disk (constructed of materials suitable to the nature of analyses to be performed), approximately 0.315-cm
(0.125-in.) 0.315 cm (0.125 in.) thick, with an outside diameter (OD) suitable to the suggested vessel ID (6.1.1 and 6.1.26.1.1 and
6.1.2) is elevated approximately 1.25 cm (0.5 in.) above the cell bottom to support the solid material sample (see Fig. 1).
6.1.5 For Option A, the cell lid and base are 1.27 cm (0.5 in.) (0.5 in.) thick and machined so they each include a lip and plug;
the plug portion fits into the ID of the humidity-cell humidity cell top/bottom, and the lip fits over the rim of the cell opening. A
hole is drilled in the center of the lid and base and tapped to accommodate a barbed NPT fitting for attachment to flexible tubing.
The tubing from the lid leads to the air-exit port bubbler described in 6.19 and 6.20. The tubing from the base drains into a
collection vessel.
NOTE 6—Lids for Option A can have an “O”-ringO-ring seal installed (machined into the plug surface) if air leakage makes it difficult to maintain
constant airflow among individual cells. Both the “O”-ringO-ring seal and the air-exit air exit port bubbler (described in 6.20) have been helpful in
D5744 − 18
FIG. 1 Side View of 16-Cell Array (Option A)
maintaining airflow through individual cells of a multiple cell multiple-cell array during the dry- and wet-air portions of the weekly cycle. However, flow
rates may still differ somewhat from cell to cell because of porosity differences between samples of differing particle-size particle size distribution.
6.1.6 Lids for Option B do not require a barbed NPT fitting. The centered hole in the Option B lid is left open to allow for
exchange of ambient air during the six-day portion of the weekly cycle. A hole is drilled in the center of the base and tapped to
accommodate a barbed NPT fitting. Leachate from the cell drains directly through this fitting into a collection vessel.
NOTE 7—The cell and particle size dimensions described above are those used commonly for assessing the potential of waste-rock samples associated
with metal-mining operations to produce acidic effluent. A “shoe box”-shaped cell design with similar dimensions is preferred by some researchers (6).
6.2 Separatory-Funnel Separatory Funnel Rack, capable of holding 500-mL or 1-L separatory funnels above the humidity cells.
6.3 Filter Media, such as a 12-oz/yd polypropylene felt characterized by 22-μm (0.009-in.) diameter filaments. The media
should be able to transmit dry air at a rate of 20 to 30 cfm 30 cfm (see Test Methods D276 and D737 for guidance).
NOTE 8—Caution must be used in the selection of filter media materials since they may affect the effluent pH and chemistry adversely. Both pyrex wool
and quartz wool retain as much as 10 to 15 g of water per g of wool (retained water tends to re-humidify the dry-air cycle to as much as 85 % relative
humidity). Additionally, pyrex wool causes the neutral effluent pH to be raised by as much as 2 pH units due to leaching of the wool (11). In addition,
pyrex (borosilicate) can contribute boron if this is a constituent of interest.
6.4 Two Riffle Splitters, with 0.63-cm (0.25-in.) and 2.5-cm (1.0-in.) wide riffles, respectively; the riffle splitter is a commonly
used device for obtaining representative splits of dry, free-flowing granular materials.
D5744 − 18
6.5 Laboratory Balance, capable of weighing to 0.1 g.
6.6 Analytical Balance, capable of weighing to 1.0 mg.
6.7 Screen, 6.3 mm (0.25 in.).
6.8 Screen, 150 mm (100 mesh).
6.9 Drying Oven—Any thermostatically controlled drying oven capable of maintaining a steady temperature of 40 6 2°C.2 °C.
6.10 pH Meter—Any pH meter with readability of 0.01 units and an accuracy of 60.05 units at 25°C;25 °C; two-channel
operation (that is, pH and Eh) is desirable.
6.11 Conductivity Meter, capable of reading in micromhos (microseimens); calibrate at 25°C.25 °C.
6.12 Separatory Funnel, 500 mL or 1 L, one per each humidity cell.
6.13 Collection Vessel (vessel such as an Erlenmeyer flask or Nalgene bottle), Vessel, vessel such as an Erlenmeyer flask or
Nalgene bottle, 500 mL or 1 L, one per each humidity cell.
6.14 Volumetric Flask, 500 mL or 1 L.
OPTION A
6.15 Digital Hygrometer/Thermometer, with a relative humidity range of 5 to 95 %, and temperature range of -40–40 to 104°C
(-40104 °C (–40 to 220°F).220 °F).
6.16 Cylindrical Humidifier, with suggested dimensions of 12.1-cm (4.75-in.) ID by 134.6-cm (53.0-in.) 12.1 cm (4.75 in.) ID
by 134.6 cm (53.0 in.) length. The following associated equipment are needed to provide saturated air for the three-day wet-air
portion of the weekly cycle:
6.16.1 A thermostatically controlled heating element to maintain the water temperature at 25°C25 °C during the wet-air cycle.
6.16.2 An aeration stone (similar to aquarium-aeration aquarium aeration equipment) or commercially available gas dispersion
fritted cylinders or disks to bubble air into the humidifier water.
6.17 Flow meter,Meter, capable of delivering air to each humidity cell at a rate of approximately 1 to 10 L/min/cell.
6.18 Oil/Water Trap, 0.01-μm, 0.01 μm, for inclusion in the feed-air line.
6.19 Air-Exit Air Exit Port Bubbler—A 50-mL Erlenmeyer flask with a rubber stopper containing a vent and air-inlet air inlet
tube (Fig. 1). The bubbler is connected to the air exit port in the humidity cell lid with flexible tubing. This helps maintain similar
positive air pressure throughout all of the humidity cells.
6.20 Flexible-Tubing Flexible Tubing Quick Disconnect—A fitted, two-piece connection placed in the middle of the air-exit air
exit port flexible tubing so that the bubbler can be disconnected from the humidity cell to facilitate the measurement of air flow
and relative humidity.
6.21 Desiccant Column, 5.1-cm (2-in.) 5.1 cm (2 in.) ID by 50.8-cm (20-in.) 50.8 cm (20 in.) length, plastic or glass cylinder
capped on both ends (one cap should be removable for desiccant replacement), with an air inlet port on the bottom and an air exit
port on the top.
6.22 Dry Air Manifold—A cylindrical manifold constructed from 2.25-in. ID schedule 40 acrylic plastic tubing, 28 in. long and
fitted with 16 NPT barbed fittings. The airline exiting the desiccant column is routed directly to the cylinder, which then supplies
dry air to each cell through an airline attached to its corresponding NPT barbed fitting. The cylindrical manifold fits atop the
separatory-funnel separatory funnel rack.
OPTION B
6.23 Environmentally-Controlled Environmentally Controlled Enclosure—Any enclosure suitably sized to accommodate the
number of samples being tested and associated equipment, and capable of maintaining consistent humidity (610 %) and
temperature (62°C).(62 °C).
6.23.1 Temperature Control—Any commercially-available commercially available heater capable of maintaining consistent
temperature within the enclosure.
6.23.2 Humidity Control—Any commercially-available commercially available humidifier and dehumidifier capable of
maintaining consistent humidity within the enclosure.
6.23.3 Instruments to Measure Temperature and Humidity—Any commercially-available commercially available manual or
digital hygrometer/thermometer (see 6.15). Temperature should be readable to at least 1°C1 °C and relative humidity to 1 %.
6.23.4 Fan—Any commercially-available commercially available fan to provide air circulation within the enclosure.
The tolerance ranges for humidity and temperature are the range of differences of maximum and minimum values from the mean of the respective data.
D5744 − 18
7. Reagents
7.1 Purity of Reagents—Reagent grade Reagent-grade chemicals shall be used in all tests. Unless otherwise indicated, it is
intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical
Society, where such specifications are available.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type III at 18 to 27°C27 °C conforming to Specification D1193. The method by which the water is prepared, that is, distillation,
ion exchange, reverse osmosis, electrodialysis, or a combination thereof, should remain constant throughout testing.
7.3 Purity of Air—The feed air line shall contain a 0.01-μm oil/water trap in advance of the flow meter.
8. Sampling
8.1 Collect the samples to be tested using available sample methods developed for the specific industry (see Practices
D75D75/D75M and E877, Guide D420, Terminology D653, and Test Methods Practice D2234/D2234M).
8.2 The sampling methodology for materials of similar physical form shall be used where no specific methods are available.
8.3 The amount of material recommended to be sent to the laboratory should be sufficient to provide 8 to 10 kg of bulk sample
for splitting, analysis, and testing (see 9.3).
NOTE 9—Additional information on theory and methods for obtaining representative samples isare contained in Pitard (16).
8.4 To prevent sample contamination or constituent loss prior to testing, store the samples in closed containers that are
appropriate to the sample type and desired analyses (see Guide D420 for guidance).
8.5 The time elapsed between sample collection and subsequent humidity cell testing should be minimized to reduce the amount
of sample pre-oxidation (see Practices D3370 for guidance). Report the length of time between sample collection and testing.
9. Sample Preparation
9.1 Air dry as-received bulk samples of solid material to prevent the additional oxidation of reactive minerals or compounds.
If air-drying air drying is not practicable, oven dry the solid material at a maximum temperature of 40°C40 °C for 24 h, or until
a constant weight is reached.
NOTE 10—Oven drying at temperatures above 40°C40 °C may introduce chemical and physical changes in certain mineral species comprising the
sample (9). These potential changes should be evaluated and accounted for in the analysis of the test data.
9.2 After reserving any coarse material needed for Test Method E2242-02 (Meteoric Water Mobility Procedure) or other
possible testing and analyses, screen the air-dried bulk samples through a 6.3-mm (0.25-in.) screen in accordance with Test Method
E276. Crush any oversize material so that 100 % passes the screen. For particles finer than 15.2 cm (6 in.), the generation of
excessive fines can be limited by stage crushing the oversize material in three steps: (1) large jaw large-jaw crusher set at 1.92 cm,
(2) small jaw small-jaw crusher set at 0.95 cm, and (3) roll crusher set at 0.64 cm. After each of the first two crushing steps, the
-0.64 cm –0.64-cm fraction is collected and the oversize is passed to the next crushing phase.
9.2.1 CautionCaution—: Crushing a bulk sample so it passes a 6.3-mm (0.25-in.) screen may change the character of the
sample by artificially increasing liberation and consequent surface areas of acid-producing and acid-consuming minerals contained
in the + 6.3-mm +6.3-mm (0.25-in.) material. A suggestion for avoiding this problem is to segregate the − 6.3-mm −6.3-mm
(0.25-in.) fraction by screening rather than crushing, and to test that fraction according to the protocol and equipment described
in this test method. The + 6.3-mm +6.3-mm (0.25-in.) material can either be stage-crushed stage crushed (as in 9.2), or tested
separately. For example, column testing could be conducted, although no standard protocol has been established for this testing.
Samples from the drill core and cuttings also present material sizing problems, which must be considered when interpreting drill
core and cuttings laboratory weathering data. The drill core must be crushed to − 6.3-mm −6.3-mm (0.25-in.) to fit the cell
described in this test method. The resulting size distribution from crushing will differ from that of run-of-mine due to differences
in fracture patterns inherent to blasting practices that produce run-of-mine material. By contrast, drill cuttings size fractions are
commonly less than 6.3-mm (0.25-in.) 6.3 mm (0.25 in.) due to the rotary-percussive nature of obtaining the sample. The effects
of particle size distribution changes resulting from the more finely crushed sample or from rotary-drill rotary drill cuttings should
be considered in the interpretation of data. In particular, particle size reduction will increase specific surface area of acid-generating
and acid-neutralizing minerals and is likely to increase liberation of these minerals. Both of these effects will tend to increase the
surface area of these minerals available for reaction. If this increase is biased towards either acid-generating or acid-neutralizing
minerals, the balance of acid-generating and acid-neutralizing reactions will shift.
9.3 Mix and divide the bulk sample to obtain a representative test unit with a weight in the range of 8 to 10 kg, using a riffle
splitter with 1-in. (2.54-cm) chutes (perform in accordance with Test Method Practice E877, Sampling and Preparation
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC.D.C. For suggestions on the testing of reagents not listed
by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MDMD.
D5744 − 18
Procedure-Riffling). Divide the test unit into eight nominal 1-kg test specimens. Store each test specimen in a resealable plastic
bag (tobag. (To prevent continued atmospheric oxidation of sulfide mineral-bearing samples, samples could be vacuum sealed or
refrigerated).refrigerated.)
NOTE 11—The dried sample should be mixed through the riffle splitter at least once before making any splits; recombine the splits resulting from the
sample mixing exercise by pouring individual splits either over each other or through the splitter again. Once the actual split is made, it is wise to re-mix
it (according to the above procedure) prior to making the next split. Mixing the sample through the riffle splitter may still result in segregation of the
sample. If segregation persists, use of a rotary sample divider is advised.
9.4 Head-Sample Head Sample Analysis—Select one 1-kg test specimen at random, and crush the dried test specimen so that
at least 95 % passes a 1.7-mm (10-mesh) (10 mesh) screen, in accordance with Test Method E276.
9.4.1 Divide the crushed test specimen in half twice, using a riffle splitter with 6.35-mm (0.25-in.) chutes (in accordance with
Test Method Practice E877, Sampling and Preparation Procedure-Riffling), and select a 250-g subsample at random for head
sample analysis.
9.4.2 Transfer the selected 250-g subsample to a ring and puck grinding mill and grind to a nominal 95 % passing a 150-μm
(100-mesh) (100 mesh) screen, in accordance with Test Method E276. Use the pulverized subsample to perform the following
determinations: (1) total sulfur, sulfide, and carbonate analyses in accordance with Test MethodMethods E1915, (2) whole rock
whole-rock and trace-element chemistry analyses, and (3) mineral characterization to identify and quantify the different mineral
species comprising the sample.
NOTE 12—Because accurate estimation of a sample’s capacity to neutralize acid (NP) requires identification of carbonate mineral speciation (that is,
calcite, dolomite, ferroan dolomite, siderite, and so forth), and quantification of calcium and magnesium content in iron-bearing minerals (that is, ankerite,
ferroan dolomite, and siderite, and so forth), these determinations are strongly recommended. It is also recommended that sample whole-rock chemistry
and mineralogy be compared to ensure that chemistry is consistent with mineralogy and vice versa. Additionally, leach extraction testing of the pre-test
sample, compared with leach extraction testing of post-test sample, may be beneficial in determining the extent of solutes released by mineral dissolution
and subsequently sequestered in secondary solid phases during testing (17).
9.5 Screen-Fraction Analysis—Select one 1-kg test specimen at random, and determine the particle size distribution in
accordance with Test Method E276. Sieve openings of 6, 10, 28, 35, 48, 100, 200, and 270 Tyler mesh are suggested.
9.6 The following analyses are recommended:
9.6.1 Determine the total sulfur, sulfide, and carbonate contents of individual size fractions in accordance with Test
MethodMethods E1915. Whole rock or trace element chemical analyses,Whole-rock or trace-element chemical analysis, or both,
may also be performed on these fractions.
9.6.2 Determine the extent of acid-generating (for example, iron sulfide, iron sulfate) and acid-neutralizing (for example,
calcium carbonate, magnesium carbonate) mineral liberation of the individual size fractions.
NOTE 13—Paragraphs 9.6.1 and 9.6.2 are recommended as best practice to quantify the amount of sulfide and carbonate minerals present in each
fraction and their degree of liberation within these fractions. The objective of the analyses described in 9.6.1 and 9.6.2 is to aid the user in correlating
drainage quality with solid-phase composition by providing more detailed description of the exposed surface areas of acid-producing and acid-neutralizing
minerals. These surface areas strongly affect the rates of acid production and neutralization. With regard to the applications of testing presented in 5.1
and 5.2, the analyses described will help: help to: (1) identify whether the material being tested will produce acidic, alkaline, or neutral effluent; (2)
determine the variation of drainage quality as a function of solid-phase composition; (3) measure the amount of estimated NP accessible in the solid; and
(4) in general, aid in predicting the environmental behavior of the solid (see Refs (8, 18, and 19)). To perform all of the determinations described in 9.6.1
and 9.6.2, a larger mass of sample material may be required than the stated 1 Kgkg (18).
9.7 Select one 1-kg test specimen at random for use in the laboratory weathering test method. Divide the test specimen into four
nominal 250-g subsamples using the riffle splitter with 25.4-mm (1-in.) chutes, and label and store in resealable plastic bags until
it is time to load the humidity cells.
NOTE 14—If the leach volume from the 1 kg 1-kg sample mass does not provide sufficient effluent to meet analytical needs, a 2-kg test specimen could
be used as long as the 0.5 : 1 or 1 : 1 0.5:1 or 1:1 leach-volume to sample-mass ratio is maintained. Split the sample between two cells. Record and then
combine recovered volumes of the weekly effluent from both cells. Also record the combined volume.
9.8 Reserve the remaining test specimens for replicated testing or to resolve disputed results (recommend sample preservation
by vacuum seal or refrigerated storage).
10. Apparatus Assembly
10.1 Option A—The humidity cells are table-mounted table mounted at a height sufficient to accommodate the placement of
both the humidifier and one collection flask for effluent collection from the bottom of each cell (Fig. 1). During the water-saturated
and
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