• Author / Uploaded
• Morched Tounsi

• Categories
• Agua
• Ciencias fisicas
• Ciencia
• Química
• Física y matemáticas

Citation preview

NOVEMBER 1998 REVISED: AUGUST 2000

Specific Gravity and Absorption of Coarse Aggregate AASHTO T-85-91 (1996) (Modified) Bulk specific gravity is the characteristic generally used for calculation of the volume occupied by the aggregate in various mixtures containing aggregate. Bulk specific gravity (SSD) is used if the aggregate is wet, that is if its absorption has been satisfied. Conversely, the bulk specific gravity (oven-dry) is used for computations when the aggregate is dry or assumed to be dry. This method is used in conjunction with AASHTO T-224 for correction for coarse particles in the soil compaction test. Modifications: 1. Weigh and record all weights to the nearest 0.1 gram. 2. Report specific gravity results to the nearest 0.001. 3. The initial drying to constant mass may be eliminated prior to soaking. KEY ELEMENTS: 1. Inspect equipment. Equipment shall include balance (6.1), wire basket (6.2), water tank (6.3), suspension apparatus (6.4), sieves (6.5), and drying oven (8.5). 2. Obtain sample. Obtain sample by AASHTO T-2 (7.1). Reduce sample according to AASHTO T-248 (7.2) to meet the minimum mass as per the table in 7.3. Reject all material passing the 4.75 mm (No. 4) sieve by dry sieving and thoroughly washing to remove dust or other coatings from the surface (7.2). 3. Immerse in water. Immerse the aggregate in distilled water at room temperature for a period of 17 ± 2 hours (8.1). 4. Obtain SSD weight. Remove the test sample from the water and roll it in a large, damp, absorbent cloth until all visible films of water are removed. Wipe the larger particles individually. Take care to avoid evaporation of water from aggregate pores during the operation of surface drying. Determine the mass of the test sample in the saturated surface dry condition. Record to the nearest 0.1 g (8.3). 5. Immediately immerse in water and weigh. Immediately place the SSD test sample in the sample container and determine its mass in water at 23.0 ± 1.7°C (73.4 ± 3°F). Take care to remove all entrapped air before determining the mass while immersed (8.4). Record to the nearest 0.1 g. (8.3) 6. Dry to a constant mass. Dry the test sample to constant mass at 110º ± 5ºC (230 + 9ºF), cool in air at room temperature 1 to 3 hours, or until the aggregate has cooled to a temperature that is comfortable to handle (8.5) and determine the mass to the nearest 0.1 g and record (8.3). 7. Calculate the bulk specific gravity (9.1.1) as follows: Bulk Specific Gravity = A / (B – C) Where: A = mass of oven dry test sample in air, g. B = mass of saturated surface dry test sample in air, g. C = mass of saturated test sample in water, g. 1

NOVEMBER 1998 REVISED: AUGUST 2000

AASHTO T-85, Continued… 8. Calculate percent absorption (9.3) as follows: Absorption = [(B - A) / A ] x 100 Where: A = mass of oven dry test sample in air, g. B = mass of saturated surface dry test sample in air, g. C = mass of saturated test sample in water, g. 9. Report results. Report specific gravity results to the nearest 0.001 and absorption to the nearest 0.1 percent (10.2).

2