Untitled Document

University of New Mexico

Civil Engineering Department

Civil Engineering Materials Laboratory, CE 305L

SPECIFIC GRAVITY & ABSORPTION OF COARSE & FINE AGGREGATES

ASTM C127 & C128

Scope

Test method ASTM C127 covers the determination of specific gravity and absorption of coarse aggregate. The specific gravity may be expressed as bulk specific gravity, saturated-surface-dry bulk specific gravity (SSD), or apparent specific gravity.

Test method ASTM C128 covers the determination of bulk, SSD specific gravity, and apparent specific gravity, and absorption of fine aggregate. The bulk and apparent specific gravity are defined according to ASTM E12, while absorption is defined in ASTM C125.

References

ASTM C127 Specific Gravity and Absorption of Coarse Aggregate

ASTM C128 Specific Gravity and Absorption of Fine Aggregate

ASTM E12 Definitions of Terms Relating Density and Specific Gravity of Solids, Liquids, and Gases

ASTM C125 Terminology Relating to Concrete and Concrete Aggregates

ASTM C29 Unit Weight and Voids in Aggregate

ASTM C566 Total Moisture Content of Aggregate by Drying

Definitions

Specific Gravity - the ratio of the mass (or weight) in air of a unit volume of material to the mass of the same volume of water at a specified temperature. Specific gravity is a dimensionless term.

Apparent Specific Gravity - the ratio of the weight in air of a unit volume of the impermeable portion of aggregate to the weight in air of an equal volume of gas-free distilled water at specified temperature.

Bulk Specific Gravity - the ratio of the weight in air of a unit volume of aggregate (including the permeable and impermeable voids in the particles, but not including the voids between particles) to the weight in air of an equal volume of gas-free distilled water at specified temperature.

Bulk Specific Gravity (SSD) - the ratio of the weight in air of a unit volume of aggregate, including the weight of water within the voids filled to the extent achieved by submersion in water for 24 hour (but not including the voids between particles) to the weight in air of an equal volume of gas-free distilled water at specified temperature.

Absorption - the increase in the weight of aggregate due to water in the pores of the material, but not including water adhering to the outside surface of the particles, expressed as a percentage of the dry weight. Dry aggregate is achieved when all uncombined water has been removed at a temperature of 110°C.

ASTM C127 (Coarse Aggregate)

Download procedure for Specific Gravity and Absorption here

Download the Excel form for Specific Gravity of Coarse Aggregate here

Apparatus

Scale (or balance)

Sample Container (wire basket)

Water Tank

Sieves (No. 4)

Drying Oven

Materials

Coarse Aggregate (>No. 4 sieve, i.e., gravel) - soaked for 24 hours, then saturated-surface-dried (SSD)

Coarse Aggregate - Oven dried at 110°C, then cooled to room temperature.

Note: The same gravel sample is used for both the SSD and oven dried states.

Scale setup for coarse aggregate

Procedure

1) Sieve dry material and reject all material finer than a number four sieve.

2) Obtain approximately 3 kg of the water soaked material and roll it in a large absorbent cloth until all visible films of water are removed. Wipe large particles individually as required to achieve a SSD condition. Weigh the test sample in his SSD condition to the nearest 0.5 g or 0.05% of the sample weight, whichever is greater.

3) Subsequently, place this SSD sample in the sample container and determine its weight in water. Be sure to tare out the sample container (wire basket) prior to placing the sample. Remove all air before weighing by shaking the basket while immersed.

4) Dry the sample to constant weight in an oven at 110°C, then allow to cool to room temperature. Weigh this dry sample of coarse aggregate.

5) Calculate the following:

a) Bulk Sp. Gr. = A/(B-C)

b) Bulk Sp. Gr. (SSD) = B/(B-C)

c) Apparent Sp. Gr. = A/(A-C)

where:

A = weight of oven dried test sample in air, g

B = weight of SSD sample in air, g

C = weight of saturated sample in water, g.

Express the above three values in terms of density, i.e., multiply the above calculated values by the density of water at 4°C (62.43 lb/ft³).

6) Calculate the percentage of absorption as follows:

Absorption, % = [(B-A)/A] *100

Report

1) Report specific gravity results to the nearest 0.001.

2) Report corresponding densities to the nearest 0.1 lb/ft³ .

3) Report the absorption to the nearest 0.1%.

ASTM C128 (Fine Aggregate)

Download the Excel form for Specific Gravity of Fine Aggregate here

Apparatus

Scale (2 kg)

Pycnometer - A flask or other suitable container into which the fine aggregate test sample can be readily introduced and in which the volume content can be reproduced within 0.1 cm³.

Mold - A metal mold in the form of a frustum of a cone with dimensions of 40 mm top diameter, 90 mm bottom diameter, and 75 mm height.

Tamper - A metal tamper weighing 340 g and having a flat circular tamping face of 25 mm diameter.

Drying Oven

Materials

Fine Aggregate (<No. 4 sieve, i.e., sand) - soaked for 24 hours

Fine Aggregate - Oven dried at 110°C, then cooled to room temperature.

Note: The same sand sample is used for both the SSD and oven dried states.

Procedure

1) Obtain approximately 1 kg of the water soaked material by the following process. Decant excess water from the pan in which the fine aggregate has been soaking, being careful to avoid loss of fines.

2) Spread sample on a flat nonabsorbent surface exposed to a gently moving current of warm air, stirring frequently to ensure uniform drying.

3) Follow the cone test for surface moisture, subsequently described; this cone test determines whether or not surface moisture is present on the fine aggregate particles. The first trial of the cone test must be made with some surface water present in the sample. Continue drying with constant stirring of the sample and cone tests at frequent intervals until the cone test indicates that the fine aggregate has reached a saturated-surface-dry condition.

4) Cone Test - Place mold, large side down, on a dry nonabsorbent surface. Place a portion of the partially dried sample loosely in the mold by filling it to overflowing. Lightly tamp the sample into the mold with 25 light drops of the tamper (each drop should start about 5 mm (0.2 in.) above the top surface of the aggregate). The tamper should free fall under gravity during each drop. Distribute the 25 drops over the surface of the sample. Remove loose sand from around the outside base and lift the mold vertically. If surface moisture is still present, the sand cone will retain its molded shape. When the molded shape slightly slumps, a saturated-surface-dry condition has been reached.

View a Quicktime Movie of wet sand test

View a Quicktime Movie of sand just before SSD conditions test

View a Quicktime Movie of sand at SSD conditions test

5) Partially fill the pycnometer with water. Immediately introduce 500 g of saturated-surface-dry fine aggregate prepared as above. Record the weight of this SSD fine aggregate placed in the pycnometer. Fill the pycnometer to 90% of capacity. Roll, invert, and agitate the pycnometer to eliminate all air bubbles (this can take 15 to 20 min). Bring the pycnometer to its calibrated capacity. Determine the total weight of the pycnometer, specimen, and water. Note: Use distilled gas-free water in the pycnometer.

6) Remove the fine aggregate from the pycnometer and dry to constant weight in an oven at 110°C, then cool to room temperature, and weigh.

7) Determine the weight of the pycnometer filled to its calibration capacity with water.

8) Calculate the following:

a) Bulk Sp. Gr. = A/(B+S-C)

b) Bulk Sp. Gr. (SSD) = S/(B+S-C)

c) Apparent Sp. Gr. = A/(B+A-C)

where:

A = weight of oven dried test sample in air, g

B = weight of pycnometer filled with water to calibration mark, g

S = weight of SSD sample in air, g (prior to placement in pycnometer)

C = weight of pycnometer with specimen and water to calibration mark, g.

Express the above three values in terms of density, i.e., multiply the above calculated values by the density of water at 4°C (62.43 lb/ft³).