TEST METHOD FOR MAGNESIUM SULFATE SOUNDNESS OF GRANULAR MATERIALS
GEOTECHNICAL TEST METHOD GTM-21 Revision #3
GEOTECHNICAL ENGINEERING BUREAU
APRIL 2007
NEW YORK STATE DEPARTMENT OF TRANSPORTATION GEOTECHNICAL TEST METHOD: TEST METHOD FOR MAGNESIUM SULFATE SOUNDNESS OF GRANULAR MATERIALS
GTM-21 Revision #3
STATE OF NEW YORK DEPARTMENT OF TRANSPORTATION
GEOTECHNICAL ENGINEERING BUREAU
APRIL 2007
EB 07-039 Page 1 of 10 TABLE OF CONTENTS
1. SCOPE...... 3
2. APPARATUS...... 3
3. MAGNESIUM SULFATE SOLUTION...... 4 A. Magnesium Sulfate...... 4 B. Mixing...... 5 C. Testing and Use...... 5 D. Solution Temperature...... 6
4. SAMPLES...... 6
5. SAMPLE PREPARATION...... 6
6. CONTROL SAMPLES...... 7
7. PROCEDURE...... 7 A. Immersion of Samples in Prepared Solution...... 7 B. Drying Samples After Immersion...... 7 C. Number of Cycles...... 8 D. Final Washing and Sieving...... 8
8. DATA AND COMPUTATIONS...... 8 A. Test Sample Gradation...... 8 B. Original Weight of Sample...... 9 C. Final Weight of Sample...... 9 D. Weight Loss...... 9 E. Percent Weight Loss...... 9 F. Weighted Average Corrected Percent Loss...... 9 G. Percent Loss Total...... 9
APPENDIX...... 10
A. SM 309 Forms...... A-1 B. Example: Use of SM 309 Forms...... B-1
EB 07-039 Page 2 of 10 1. SCOPE
This method describes the procedure to be followed in determining the soundness of granular materials by their resistance to disintegration under the action of repeated wetting and drying using a saturated solution of magnesium sulfate.
2. APPARATUS
A. Sieves - Set of five (5) sieves conforming to the following sizes: 2 in., 1 in., ½ in., ¼ in., No. 10 (50 mm, 25 mm, 12.5 mm, 6.3 mm, 2.00 mm), and separator pans. The sieves shall conform to the requirement of AASHTO M-92-91, pg. 87 - Table No. 1.
B. Sieve Shaker - Motor-driven sieve shaker equal to W. S. Tyler "Ro-Tap" equipped with an automatic timer capable of controlling a three minute timing requirement.
C. Sample Splitter - Sampler splitter equal to Soiltest Inc. Model CL-286.
D. Sample Baskets - Wire mesh basket-type containers used to retain samples during testing. No. 4 (4.75 mm) U.S. Standard wire mesh shall be used to construct the baskets holding plus ¼ in. (6.3 mm) fractions; No. 14 (1.4 mm) U. S. Standard wire mesh shall be used for the baskets holding fractions finer than ¼ in. (6.3 mm).
The baskets of non-corrosive wire mesh (stainless steel, brass, etc.) shall be constructed so as to permit free access of the solution to the samples as well as free drainage.
E. Balances - Balances accurate and readable to 1 g. All weighing shall be determined to the nearest gram.
F. Drying Oven - Oven(s) of mechanical, forced convection, cross-flow type, capable of continuously maintaining a drying temperature of 2309 F (1105 C), and also capable of meeting a minimum performance requirement for evaporation rate (see Note 1).
G. Hydrometer - Hydrometer capable of measuring specific gravities of heavy liquids between the range of 1.200 to 1.420 in divisions of 0.002.
H. Cylinder – 1.1 qt (1000 mL) clear graduated cylinder of sufficient height to take hydrometer readings.
I. Thermometer - General laboratory mercury thermometer capable of measuring temperatures between the range of 68 to 140 F (20 to 60 C) in one degree increments.
EB 07-039 Page 3 of 10 J. Electric Mixing Device and Vessel (optional) - Device capable of stirring water and magnesium sulfate in a mixing vessel. The vessel shall also have the ability to control the solution temperature.
K. Holding Tank - Non-corrosive container with cover capable of holding magnesium sulfate solution.
L. Wash Tank - Container of suitable size to hold sample baskets such that hot water introduced through inlet nozzles can circulate freely within and around baskets causing complete sample washing.
M. Immersion Containers or Bath Tank - Non-corrosive containers or tank of suitable size to hold sample baskets during the immersion period. Suitable provisions shall be made for controlling and maintaining the specified solution testing temperature of 753 F (242 C).
3. MAGNESIUM SULFATE SOLUTION
A. Magnesium Sulfate, MgSO 4 7H20 - Technical, CP or USP Grades of the Heptahydrate (Epsom Salt) shall be used in preparing the solution.
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Note 1: The procedure for determining the evaporation rate shall be as follows: (1) Bring the empty oven to 2309 F (1105 C); (2) Place five 0.8 qt (800 mL) low-form Griffin beakers, each containing 1 lb. (500 g) of water at an initial temperature of 703 F (212 C), on each shelf of the oven - one in each corner and one in the center of each shelf; (3) Close the oven for a period of five hours. Maintain oven at to 2309 F (1105 C); (4) After five hours, remove the beakers from the oven, cover, allow to cool to room temperature and determine the loss of water from each beaker. The average loss from all beakers shall be at least 0.6 lb. (250 g) for the five- hour period. Any oven incapable of meeting this minimum requirement for evaporation rate is not acceptable for use in this test method.
EB 07-039 Page 4 of 10 B. Mixing - Mix approximately 100 lbs. (45 Kg) (net) of magnesium sulfate, with 10 gal. (38 L) of water at approximately 120 F (49 C). (Larger or smaller quantities of solution may be made by using the ratio of approximately 2.7 lbs. (1225 g) of magnesium sulfate per liter of water.) It may be necessary to vary the above quantities to obtain the required specific gravity of not less than 1.295, nor more than 1.308. Place the above quantities into the mixing vessel and set the electric mixing device in place. Maintaining a minimum temperature of approximately 120 F (49 C), mix until saturation is achieved (approximately 50 minutes). Cool until the solution reaches 86 F (30C), at which time turn off the mixer and immediately transfer the solution to a holding tank. The solution must then stand at the test temperature of 753 F (242 C) for at least 48 hours before use.
Draw off a 1.1 qt. (1000 mL) of solution into a cylinder immediately after transferring to the holding tank. Allow this cylinder of solution to cool to the test temperature and take specific gravity only as a check to see if the solution is within the specified requirements (see Note 2). After checking, pour the solution from the cylinder back into its respective holding tank.
C. Testing and Use - After the minimum 48 hour stabilization period, draw off 1.1 qt. (1000 mL) of solution from the holding tank. Mark the cylinder so that it corresponds with the appropriate holding tank. Take and record the specific gravity on each cylinder daily, from each batch, until the samples utilizing that respective solution have completed their cycles. The specific gravity of the solution shall be not less than 1.295 nor more than 1.308 when used for testing. If a partial batch of solution is left over and is to be used, take a new cylinder of solution and check the specific gravity as noted above.
At the completion of the last cycle, the solution in the immersion containers shall be discarded. However, if a bath system is used the solution may be discarded or filtered to remove discoloration. The specific gravity shall be maintained within the required range.
Note: If at any time excessive crystallization occurs, the solution shall be remixed at a temperature above 120 F (49 C) and placed into a clean holding tank. A 1.1 qt. (1000 mL) of solution shall then be drawn off and periodically checked as previously noted for specific gravity monitoring. If the initial reading of the remixed solution is less than 1.303, the solution shall be discarded. ______
Note 2: The specific gravity taken at this time may be above the upper limit of the requirements, but must be within these requirements after the 48 hour stabilization period. It is suggested that this check value of the specific gravity not be lower than 1.303 in order to stay within the specified requirements at the completion of testing.
EB 07-039 Page 5 of 10 D. Solution Temperature - The solution temperature shall be maintained at 753 F (242 C). The test solution temperature shall be checked periodically throughout the day and recorded.
4. SAMPLES
A. The field sample(s) shall be obtained for testing in accordance with the appropriate Departmental publication in effect.
5. SAMPLE PREPARATION
A. The total field sample shall be separated into plus and minus ¼ in. (6.3 mm) fractions. A standard sieve analysis shall then be performed in accordance with the appropriate Departmental publication to determine the total sample gradation and segregate the sizes. For soils with significant amounts of silt and/or clay particles clinging or adhering to the plus ¼ in. (6.3 mm) material, adequate care shall be taken to make sure that the fines are thoroughly removed.
B. The material to be tested shall be separated in each size range and passed through a sample splitter to obtain representative samples consisting of the test weights required as listed in E. below. Sufficient excess should be split at this time to compensate for materials lost during sieving.
C. The material obtained from B. above shall be re-sieved for a period of 3 minutes on the sieve shaker to obtain exact "before test" sample weights.
D. Weigh the test samples and set aside or discard excess material over the maximum test weight required for each sample in E. below.
E. Final "before test" sample weights shall be as follows:
2 in. to 1 in. (50 mm to 25 mm) size 2100 100 g 1 in. to ½ in. (25 mm to 12.5 mm) size 600 30 g ½ in. to ¼ in. (12.5 mm to 6.3 mm) size 300 15 g
Materials with 90 percent or more passing the ¼ in. (6.3 mm) screen in the standard sieve analysis in A. above shall have an additional test sample fraction consisting of the following size and weight after being washed and thoroughly dried:
¼ in. to No. 10 (6.3 mm to 2.0 mm) size 100 10 g
EB 07-039 Page 6 of 10 Where the original field sample does not provide the minimum "before test" sample weights in one (or more) size ranges, as listed above, no test will be run on that (or those) fractions. The remaining fractions shall be tested and will comprise the total loss of the sample. The final "before test" sample weights shall be recorded on the appropriate form and used for computations.
6. CONTROL SAMPLES
A. The control samples shall be used as a monitoring system to detect any deviations in the testing process. This material shall be a homogeneous material which has a pre- determined loss range.
B. The control material shall be sieved to the following "before test" sample weights after being washed and thoroughly dried:
½ in. to ¼ in. (12.5 mm to 6.3 mm) material Two – 600 g samples ¼ in. to No. 10 (6.3 mm to 2.00 mm) material One – 100 g sample
C. The three control samples shall be tested at the same time, under the same conditions and with the same solution as the test samples being monitored.
D. The evaluation of the control sample test results and the subsequent actions taken shall be determined by the Soils Engineering Laboratory Supervisor.
7. PROCEDURE
A. Immersion of Samples in Prepared Solution - The samples (test and control) in their wire mesh sample baskets (Section 2 D.) shall be placed in the immersion containers and allowed to soak in the saturated solution (Section 3) for a period of 17 1 hours at the specified temperature of 753 F (242 C).
B. Drying Samples After Immersion - After soaking for the required period (A. above), the samples in their sample baskets shall be removed from the solution and allowed to drain a minimum of 15 minutes before placing in the drying oven (Section 2 F.). The oven shall be preheated at least 1/2 hour to the temperature of 2309 F (1105 C), after which the samples in their sample baskets shall be placed in the oven. The oven(s) shall be loaded so that air can flow freely in and around the samples. Sample baskets shall not be stacked, nested, nor otherwise crowded too closely together within the oven. The samples shall be dried for a minimum of five (5) hours, and then air-cooled to the testing temperature prior to re-immersion in the magnesium sulfate solution.
C. Number of Cycles - A cycle is defined as one complete immersion followed by one complete drying period. A complete test shall consist of four (4) cycles.
EB 07-039 Page 7 of 10 D. Final Washing and Sieving - After completion of the drying portion of the last cycle, the samples (test and control) shall be washed for a minimum of one hour in the wash tank. The wash water shall have a temperature of 12020 F (4911 C). A check shall be made for the presence of magnesium sulfate in the wash water. Washing shall be considered complete when the addition of a few drops of a 10 percent Barium Chloride solution to a small sample of the wash water does not produce a cloudy white precipitate.
After washing, each sample shall be oven dried for a minimum of five (5) hours at 2309 F (1105 C) and then allowed to cool. Using the same sieve sizes as originally employed for preparation, each sample shall be sieved for three (3) minutes on the sieve shaker and reweighed. Record the weight of material retained on each sieve on the appropriate form. If more than one sample is to be sieved at one time, separator pans shall be used beneath each sieve in the nest to prevent the loss from one sample being retained on a finer sieve.
8. DATA AND COMPUTATIONS
The test form shall include all necessary data to complete computations for the determination of the total percent loss based upon the following size ranges adopted for this test:
2 in. to 1 in. (50 mm to 25 mm) 1 in. to ½ in. (25 mm to 12.5 mm) ½ in. to ¼ in. (12.5 mm to 6.3 mm) ¼ in. to No. 10 (6.3 mm to 2.00 mm)
Form SM 295c uses US Customary Units (lbs.) for recording the larger weights (test sample gradation breakdown) and International System of Units (g) for recording the smaller weights (original & final weight, weight loss, etc.).
The following are specific instructions for completing the test form:
A. Test Sample Gradation - The test sample gradation excludes all material not within the size ranges tested. The test sample gradations are the retained weights as determined in Section 5 A. for the size ranges listed above. The sum of these weights is considered to be the "total" test sample weight. Any size range which does not provide the minimum amount of material to test (see Section 5 E.) shall also be excluded from the "total." To determine the percentage in a particular size range, divide the weight of material for that size range by the "total" and multiply by 100 (see examples). B. Original Weight of Sample - The original weight of each sample for each size range is the "before test" weight, as determined in Section 5 C.
EB 07-039 Page 8 of 10 C. Final Weight of Sample - The final weight of sample for each size range is the weight of each sample at the end of a completed test, as determined in Section 7 D.
D. Weight Loss - The weight loss for each size range is obtained by subtracting (C) from (B) above.
E. Percent Weight Loss - The percent weight loss for each size range is obtained by dividing (D) by (B) above and multiplying by 100.
F. Weighted Average Corrected Percent Loss - The weighted average corrected percent loss is obtained by multiplying the percent weight loss for each size range (E) by the corresponding percent retained obtained in (A).
G. Percent Loss Total - The total percent loss is obtained by adding the weighted average corrected percent loss, as calculated in (F) above, for all size ranges tested.
EB 07-039 Page 9 of 10 APPENDIX
EB 07-039 Page 10 of 10 APPENDIX A
EB 07-039 A-1 APPENDIX A
EB 07-039 A-2 APPENDIX B
EB 07-039 B-1 APPENDIX B
EB 07-039 B-2