Standard Method of Test for Volumetric Absorption & Specific Gravity Test Procedure SPECIFIC GRAVITY AND ABSORPTION OF AGGREGATE BY VOLUMETRIC IMMERSION METHOD AASHTO TP XXXX 1. SCOPE 1.1. This method covers the determination of bulk and apparent specific gravity at standard temperature, and absorption of fine aggregate. 1.2. This method determines the bulk specific gravity, the apparent specific gravity, the bulk specific gravity on the saturated aggregate, and the absorption. 1.3. This standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 132, Terms Relating to Density and Specific Gravity of Solids, Liquids and Gases. M 231, Weighing Devices Used in the Testing of Materials R 1, Use of the International System of Units T 2, Sampling of Aggregates T 19M/T 19, Bulk Density ( Unit Weight ) and Voids in Aggregate T 248 Reducing Samples of Aggregate to Testing Size 2.2. ASTM Standards C 125 Terminology Relating to Concrete and Concrete Aggregates C 670 Preparing Precision and Bias Statements for Test Methods for Construction Materials 3. SIGNIFIANCE AND USE 3.1. Bulk specific gravity is the characteristic generally used for calculations of the volume occupied by the aggregate in various mixtures containing aggregate including portland cement concrete, bituminous concrete, and other mixtures that are proportioned or analyzed on an absolute volume basis. Bulk specific gravity is also used in the computations when the aggregate is dry or assumed to be dry. 3.2. Apparent specific gravity pertains to the relative density of the solid material making up the constituent particles not including the pore space within the particles that is accessible to water. This value is not widely used in construction aggregate technology.
3.3. Absorption values are used to calculate the change in the mass of an aggregate due to water absorbed in the pore spaces within the constituent particles, compared to the dry condition, when it is deemed that the aggregate has been in contact with water long enough to satisfy most of the absorption potential. The laboratory standard for absorption is that obtained after submerging dry aggregate for approximately 15 hours in water. Aggregates mined from below the water table may have a higher absorption when used, if not allowed to dry. Conversely, some aggregates when used may contain an amount of absorbed moisture less than the 15 hours soaked condition: For an aggregate that has been in contact with water and that has free moisture on the particle surfaces, the percentage of free moisture can be determined by deducting the absorption from the total moisture content determined by T 255 drying. 4. EQUIPMENT 4.1. Large volume flask with relatively small, calibrated neck that can be read to a precision of at least 0.1% of the volume of the sample material being tested (See Appendix I). These flasks are available from Humboldt Manufacturing Company, 7300 W. Agatite Avenue, Norridge, IL 60706. Note 1: The flask to be used for fine aggregate will have a neck approximately 1 inch in diameter. The flask used for coarse aggregate will have a neck approximately 2 inches in diameter. 4.2. Scale, readable to 0.1 grams; 4.3. Minimum 18 long Rod with dry, absorbent cotton swab; 4.4. Timer that can be read to the nearest second, and that can measure elapsed time up to 24 Hrs. 5. CALIBRATION OF FLASK 5.1. Determine the empty weight of the flask, in grams; 5.2. Fill the Flask with distilled water at 70.0 o F +/- 1 o F until the bottom of the meniscus is exactly even with the 10 mark; 5.3. Weigh the filled flask, in grams; 5.4. Subtract the empty weight of the flask, in grams; 5.5. Subtract the 10 milliliters to get the value back to 0; 5.6. This is the base volume of water, in milliliters. 6. SAMPLING 6.1. Sampling shall be accomplished in general accordance with T 2. 7. PREPARATION OF TEST SPECIMEN 7.1. Obtain approximately two kilograms of the aggregate from the sample using the applicable procedures described in T 248.
7.2. Dry it in a suitable pan or vessel to constant mass at a temperature of 110 +/- 5 o C (230 +/- 9 o F). Allow it to cool to comfortable handling temperature, without allowing it to absorb any water from the surrounding environment. 8. TEST PROCEDURE 8.1. When using normal weight aggregate, weigh out 1200 +/- 10 grams of ovendry sand or 5000 +/- 50 grams of coarse aggregate to be tested. Make sure that the sample accurately represents the material to be evaluated. If testing lightweight aggregate, reduce the amount of material weighed out to 600 +/- 10 grams. 8.2. Fill the flask approximately ½ full, by height, with distilled water. 8.3. Measure out, but do not add, approximately 250 grams of distilled water; Note 2: The water in 8.2 and in 8.3 will probably need to be adjusted for the individual flask being used. It is important that during the filling process, the combined initial volume of water and the dry soil not plug the neck of the flask. Therefore, the following procedure is intended to allow sufficient water for the aggregate to become completely submerged, but to not rise into the narrow neck of the flask. Holdback water is then added to bring the initial water level after all of the aggregate and the holdback water has been added into the calibrated portion of the neck. 8.4. Dry the neck of the Flask with a dry absorbent swab; Note 3: If the neck is not completely dry, then the finer portions of the sample get clogged up on the water droplets, and tend to plug the neck of the flask as the sample is being poured in. Note 4: It is recommended that an outside funnel not be used. The sand has a tendency to plug the smaller hole of the funnel, where it typically pours through the built in funnel without plugging. 8.5. Pour the aggregate sample into the Flask as quickly as possible, but without plugging the neck; 8.6. Start the timer immediately when the first stone hits the water in the flask; 8.7. After all of the sample has been poured into the flask, immediately pour in the holdback water measured out in 8.3 so that the final water level is sufficiently far up the calibrated neck to allow for accurate readings while the water level drops to its anticipated final level; 8.8. Do not shake, agitate or otherwise disturb the flask at this time. 8.9. Take the initial reading 30 seconds after the first particle has entered the water; 8.10. Place the flask on a scale, and obtain the total weight of the flask, aggregate and water; 8.11. Aggressively shake, roll and otherwise agitate the flask so that all of the air is allowed to escape. A plug must be placed into the neck of the coarse aggregate flask to prevent loss of water during the shaking and agitation of the flask. Continue shaking and agitating the flask until 3 minutes has elapsed. 8.12. Allow the flask to remain undisturbed for 2 minutes;
8.13. Obtain and record the reading at 5 minutes; 8.14. Repeat steps 8.10 through 8.12 to obtain additional readings at 10 minutes, 30 minutes, 60 minutes, 2 hours, 4 hours, and 25 +/- 1 hours. Make sure to agitate all of the air out of the sample, as required in 8.11, and allow the flask to settle for at least 2 minutes before taking each reading. Note 5: It is extremely important that all air released during the soak period be completely eliminated from the flask before taking the final reading. Make sure that the flask has been thoroughly and completely shaken and agitated, and then left undisturbed to allow all of the air to escape from the flask until there is absolutely no air left in the system. Take as much time as required to completely eliminate all of the air. 8.15. Add the base reading obtained from calibrating the flask to each of the individual readings; 8.16. Plot the readings on semi-log paper with the x-axis being time on the logarithmic scale. _ 9. ABSORPTION 9.1. Calculate the absorption as follows: Absorption, percent = [(V i - V final )/W d ] x 100 Where: V i = Initial Reading (The calibrated water volume at 0 plus the initial reading), ml; V final = Final Reading (The calibrated water volume at 0 plus the final reading), ml; W d = Original dry weight of sample, g. 10. SATURATED BULK SPECIFIC GRAVITY (BSG ssd ) 10.1. Calculate the Saturated Bulk Specific Gravity as follows, BSG ssd = (W d + W abs )/[V i V w ] Where: W abs = Water absorbed into the sample, (V i V f ), ml; W f = Weight of flask, g; V w = Volume of water [W T (W d + W f )], ml.; W T = Total weight of flask, water and sample, g; 11. DRY BULK SPECIFIC GRAVITY (BSG d ) 11.1. Calculate the Dry Bulk Specific Gravity as follows, BSG d = W d /(V i V w ) 12. APPARENT DRY SPECIFIC GRAVITY (ASG d ) 12.1. W d /[(W d + W f + V f ) (W T - R final )] Where: V f = calibrated volume of flask, ml.
R final = Final direct reading, ml. 13. CONVENTIONAL ABSORPTION 13.1. Use the Correlation Equation shown in Appendix II to calculate the Conventional Absorption as follows, Conventional Absorption, percent = [(Absorption x 1.8243) + 0.0038] x 100
APPENDIX I: Typical Flask APPENDIX II STATISTICAL CORRELATION WITH T 84 6.00% Absorption Comparison (Sand Only) 5.00% T 84 Absorption 4.00% 3.00% 2.00% 1.00% 0.00% y = 1.8243x + 0.0038 R 2 = 0.818 0.00% 1.00% 2.00% 3.00% 4.00% 5.00% 6.00% Phunque Absorption