Specific gravity of coarse aggregate is required to find out the aggregate density compared with water. We described the procedure of specific gravity test of coarse aggregate as per IS Code with limits, formula, and calculations.

**What is Specific Gravity of Coarse Aggregate?**

The specific gravity of aggregate is its density compared with water density. Specific gravity value of an aggregate represents how much dense the aggregate is compared with water.

**Why Specific Gravity Test of coarse aggregate Required?**

- For concrete, asphalt or any mix design where aggregate is used.
- By specific gravity, we can guess its quality like Aggregate impact value, Abrasion, Bulk density, etc..

**Specific Gravity of Coarse Aggregate IS Code**

IS Code for Aggregate specific gravity is IS 2386 part 3.

**Apparatus and Tools Required for Aggregate specific gravity test**

- Weighing balance ( least count 0.5 gram, capacity not less than 3000 gram).
- Hot air oven to maintain 100 to 110-degree centigrade.
- Wire basket ( 6.3 mm mesh )
- Non-absorbent plate

**Preparation Before Specific Gravity Test**

- A setup of weighing balance, stand, wire basket fitted with wire and water container to be prepared.
- Attachment wire ( wire basket to weighing balance ) dia should not exceed 1 mm.
- Wire basket shall be hung in a container kept below and shall be attached with using balance above for weight.
- Container shall be full of water minimum 50 mm above from the top of the wire basket.

**Procedure of Specific Gravity test of Coarse Aggregate**

- Take aggregate for the test not less than 2000 grams from the total sample by mixing it.
- Wash the aggregates to remove fine particles from aggregate surface and drain water for at least 5 minutes.
- After drain water, keep the aggregate in wire basket which already submerged in water.
- After aggregate placed in the wire basket, we have to remove the entrapped air bubbles stuck on the surface of the aggregates.
- To remove air bubbles we have to lift wire basket with aggregates approximately 25 mm and drop it, this operation shall be repeated 25 times in 25 seconds, means one drop per second.
- Leave aggregates in water for 24 +/- 0.5 hours.
- Immediately after 24 hours, Take the weight of the wire basket with aggregate. ( weight a1)
- Shift the aggregates from wire basket to non-absorbent plate.
- Return the wire basket to water container and repeat raise 25 mm above and drop minimum 5 times to ensure no entrapped air is there.
- Note down the weight of the empty wire basket in the water. ( weight a2)
- Weight of aggregate in the water a = weight a1 – weight a2.
- We need weight in water, surface saturated dry weight and oven-dried weight for specific gravity and apparent specific gravity value of Aggregate.
- Aggregate shall be spread on a non-absorbent plate and plate shall be placed in air.

**Careful while SSD**

- Avoid aggregates from sunlight or hot air.
- Do not use any water-absorbent cloth, it can absorb moisture from aggregate pores. It can change the Aggregate specific gravity value.
- While drying turns over the aggregates one by one.
- Immediately after dry, the surface of aggregates take the weight, It is SSD weight ( surface saturated dry weight ). note down ( weight b )

- Place these aggregates in a hot air oven for 25 +/- 0.5 hours.
- Maintain the temperature between 100 to 110 degrees centigrade in the oven.
- After 24 hours keep out aggregates and allow it to be cool in atmosphere temperature for at least 10 minutes.
- Take the weight of oven-dried aggregates. (weight c).

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**Specific Gravity of Coarse Aggregate Calculations & Formula**

Specific gravity of Aggregate = c / ( b – a ),

Apparent specific gravity of Aggregate = ( b – c ) / c

where

c – oven-dried weight

b – surface saturated dry weight

a – weight in water

**Specific Gravity of Coarse Aggregate Limits**

**Specific Gravity of Coarse Aggregate Standard Values**

The limit of specific gravity of coarse aggregate is between 2.0 to 3.0.

**Specific Gravity Units**

There are no units of specific gravity because it’s a comparison between aggregate density and water density.

**Viva Questions on Specific Gravity of Coarse Aggregate**

Q.1 What is Specific gravity?

Ans. The specific gravity of aggregate or any other material is its density compared with water density. Specific gravity value of an aggregate represents how much dense the aggregate is compared with water.

Q.2 What is the IS code used for Specific gravity test of aggregate?

Ans. IS 2386 part 3 used for specific gravity of aggregate.

Q.3 What is the formula of specific gravity?

Ans. Specific gravity formula c / ( b – a ),

where

c – oven-dried weight

b – surface saturated dry weight

a – weight in water

Q.4 What is the unit of specific gravity?

Ans. There are no units of specific gravity because it’s a comparison between aggregate density and water density.

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**Read More:**

Specific Gravity Test of Fine Aggregate Procedure by Pycnometer

Loose and Compacted Bulk Density Test Procedure of Aggregate

Water Absorption Test of Coarse, Fine aggregate [2019]

Aggregate Impact Test full procedure [Update-2019]

Initial and Final Setting Time of Cement by Vicat [Update-2019]

Concrete Mix Design – M40, M60 as per IS [Update-2019]

**Students Corner**

The volume measurement comprises the total volume of the aggregate particles as well as the volume of the water-permeable cavities.

Since it contains the water-permeable void volume, the specific volumetric weight is less than the **apparent specific** volumetric weight.

The volume measurement comprises the total volume of the aggregate particles as well as the volume of the water-permeable cavities.

Since it contains the water-permeable void volume, the specific volumetric weight is less than the apparent specific volumetric weight.

The specific gravity is the ratio of the weight of a given aggregate volume to the weight of an equal volume of water.

This is the measure of the strength or quality of the material. Low specific gravity aggregates are generally weaker than higher specific gravity aggregates.

There are no minimum or maximum values for specific gravity or absorption in the construction of Superpave mixtures.

The specific gravity is rather an overall quality required to calculate the required volume.

Some government agencies specify a specific minimum aggregate weight or maximum water absorption capacity to control the quality of the aggregate.

The addition of a chemical accelerator (generally calcium chloride) to the mixture results in the desired conditions.

The stated amount is usually 2 percent of the cement weight and rarely more than 3 percent. The final strength of concrete is not affected by the use of this chemical.

As can be seen, the precision estimates vary considerably from year to year, in part due to the use of different aggregated sources in the program.

It should be noted, however, that the Proficiency Sample Program has been using a different method of data validation since 2006.

The new method detects more outliers and leads to precision estimates that are smaller than those reported in previous years and those mentioned in the current standards.

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