ASTM D5744-12
Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell

Standard No.

ASTM D5744-12

Release Date

2012

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM D5744-13

Latest

ASTM D5744-18

Scope

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.

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 NP accessible in a mine-rock sample to neutralize acid and maintain 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.

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.

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 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.

Fundamental assumptions governing Options A and B of the procedure:

Option AAn 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 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 concentr........

ASTM D5744-12 history

• 2018 ASTM D5744-18 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 2013 ASTM D5744-13e1 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 2013 ASTM D5744-13 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 2012 ASTM D5744-12 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 2007 ASTM D5744-07e1 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 2007 ASTM D5744-07 Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell
• 1996 ASTM D5744-96(2001) Standard Test Method for Accelerated Weathering of Solid Materials Using a Modified Humidity Cell
• 2001 ASTM D5744-96 Standard Test Method for Accelerated Weathering of Solid Materials Using a Modified Humidity Cell