Specific Gravity Of Coarse And Fine Aggregate 6s6n44

Transportation Engineering laboratory, IITG

& Fine Aggregate

EXPERIMENT NO. NAME OF THE EXPERIMENT: SPECIFIC GRAVITY OF COARSE AND FINE AGGREGATE AIM OF THE EXPERIMENT: To determine the specific gravity of coarse and fine aggregates FINE AGGREGATES TEST DESCRIPTION: The fine aggregate specific gravity test is used to calculate the specific gravity of a fine aggregate sample by determining the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water. The fine aggregate specific gravity test measures fine aggregate weight under three different sample conditions:   

Oven-dry (no water in sample) Saturated surface dry (water fills the aggregate pores) Submerged in water (underwater)

Using these three weights and their relationships, a sample’s apparent specific gravity, bulk specific gravity and bulk SSD specific gravity as well as absorption can be calculated. APPARATUS REQUIRED FOR THE TEST: 1. Balance: A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 kg. 2. Oven: A well ventilated oven thermostatically controlled to maintain a temperature of 1000C to 1100C. 3. Glass vessel or jar: A wide-mouthed glass vessel such as jar of about 1.5 liters capacity. 4. Cloth: Two dry soft absorbent cloths, each not less than 75 cm × 45 cm. 5. Tray: A shallow tray of area not less than 325 cm2. 6. Container: An airtight container large enough to take the sample.

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Transportation Engineering laboratory, IITG

& Fine Aggregate

Fig. 1 Pycnometer RELEVANT CODES: IS 2386 (Part III)-1963 Methods of Test for aggregates for Concrete; Specific Gravity, Density, Voids, Absorption and Bulking; Bureau of Indian Standards TEST PROCEDURE: 1.The sample should be screened on a 10 mm IS sieve, thoroughly washed to remove particles of dust and immersed in distilled water in the glass vessel . It shall be immersed at a temperature of 22 to 320C for 24 ±0.5 hours. 2. The vessel shall be overfilled by adding distilled water and the plane ground glass slid over so as to ensure that no air is trapped in the vessel. The outer side of the vessel shall be dried and weighed (A). 3. The vessel shall be emptied and aggregate allowed to drain. Refill the vessel with distilled water and weighed (B). 4. The aggregate shall be placed on a dry cloth and gently surface dried with the cloth, transferring it to a second dry cloth when first will remove no further moisture. Then it is left exposed to atmosphere not less than 10 minutes until it appears to be completely surface dry. The aggregate shall then be weighed (C). 5. The aggregate shall be placed in the oven in the shallow tray, at a temperature of 100 to 1100C for 24±0.5 hours. It shall be then being cooled in airtight container and weighed (D). PRECAUTIONS:  The determination of SSD conditions can be difficult. If the sample is actually still wet on the surface then the mass of the SSD sample will be higher than it ought to be, which will cause a lower calculated bulk specific gravity. Conversely, if the sample is beyond SSD and some of the pore water has evaporated (which is more likely), the mass of the SSD sample will be lower than it ought to be, which will cause a higher calculated bulk specific gravity . Page 2 of 5

Transportation Engineering laboratory, IITG

    

& Fine Aggregate

Use hand gloves while removing containers from oven after switching off the oven. Thoroughly clean & dry the container before testing. Special care should be taken that no outer air enters in the pycnometer. Use apron & safety shoes at the time of testing. All parts of the equipment should always be kept clean. COARSE AGGREGATES

TEST DESCRIPTION: The coarse aggregate specific gravity test is used to calculate the specific gravity of a coarse aggregate sample by determining the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water. The coarse aggregate specific gravity test measures coarse aggregate weight under three different sample conditions:   

Oven-dry (no water in sample) Saturated surface-dry (SSD, water fills the aggregate pores) Submerged in water (underwater)

Using these three weights and their relationships, a sample’s apparent specific gravity, bulk specific gravity and bulk SSD specific gravity as well as absorption can be calculated. APPARATUS REQUIRED FOR THE TEST: 1. Balance: A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 g, and of such a type as to permit the weighing of the vessel containing the sample to be suspended from the beam and weighed in water. 2. Oven: A well ventilated oven thermostatically controlled to maintain a temperature of 100 to 110°C. 3. A wire basket of not more than 6.3mm mesh or a perforated container of convenient size, preferably chromium plated and polished, with wire hangers not thicker than one millimeter for suspending it from the balance.

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Transportation Engineering laboratory, IITG

& Fine Aggregate

Fig 2 Balance with a wire

basket

4. A stout watertight container in which the basket may be freely suspended. 5. Two dry soft absorbent cloths each not less than 75 cm  45 cm. 6. A shallow tray of area not less than 650 cm2. 7. An airtight container of capacity similar to that of the basket.

RELEVANT CODES: IS 2386 (Part 3) 1963: Method of test for aggregates for concrete (Part III) specific gravity, density, voids, absorption and bulking TEST PROCEDURE: 1. The sample shall be thoroughly washed to remove finer particles and dust, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22°C and 32°C with a cover of at least 5 cm of water above the top of the basket. 2. Immediately after immersion the entrapped air shall be removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and aggregate shall remain completely immersed during the operation and for a period of 24 ± 0.5 hours afterwards. 3. The basket and the sample shall then be jolted and weighed in water at a temperature of 22 to 32oC if it is necessary for them to be transferred to a different tank for weighing, they shall be jolted 25 times as described above in the new tank before weighing (w1).

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Transportation Engineering laboratory, IITG

& Fine Aggregate

4.The basket and the aggregate shall then be removed from the water and allowed to drain for a few minutes, after which the, aggregate shall be gently emptied from the basket on to one of the dry clothes, and the empty basket shall be returned to the water, jolted 25 times and weighed in water (w2). 5. The aggregate placed on the dry cloth shall be gently surface dried with the cloth, transferring it to the second dry cloth when the first will remove no further moisture. It shall then be spread out not more than one stone deep on the second cloth and exposed to the atmosphere away from direct sunlight or any other source of heat for not less than 10 minutes, or until it appears to be completely surface dry (which with some aggregates may take an hour or more). 6. The aggregate shall be turned over at least once during this period and a gentle current of unheated air may be used after the first ten minutes to accelerate the drying of difficult aggregates. The aggregate shall then be weighed (B). 7. The aggregate shall then be placed in the oven in the shallow tray, at a temperature of 100 to 110°C and maintained at this temperature for 24 ± 0.5 hours. It shall then be removed from the oven, cooled in the airtight container and weighed (C). PRECAUTIONS:  If the aggregate is not oven-dried before soaking, specific gravity values may be significantly higher. This is because in the normal procedure the water may not be able to penetrate the pores to the center of the aggregate particle during the soaking time. If the aggregate is not oven-dry to start, the existing water in the aggregate pore structrure may be able to penetrate further into the pores.  Make sure to use cloth and not paper towels. Paper towels may absorb water in the aggregate pores. Use hand gloves while removing containers from oven after switching off the oven. Thoroughly clean & dry the container before testing. Special care should be taken that no outer air enters in the pycnometer. Use apron & safety shoes at the time of testing.  All parts of the equipment should always be kept clean.    

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