** Specific gravity and Water Absorption Test of Aggregates** are major **important **tests to be **performed **on **aggregate**. These two **parameters **or properties of **aggregate **play an **important **role in the **mix design of concrete**. As we know that aggregate occupies **70 to 80% **volume of concrete, its **testing **becomes **essential **before **use**.

As per IS: **2386 (Part III) – 1963** – ** (Indian Standard- Methods of Test for Aggregates for Concrete – Specific Gravity, Density, Voids, Absorption, and Bulking),**

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## Specific Gravity and Water Absorption Test of Coarse Aggregate

**Specific Gravity **and **Water Absorption **Test of Coarse **Aggregate **are two important tests of coarse **aggregate **used in **construction**. Let **discuss** them in **details**,

**Specific Gravity**

“**Specific **Gravity is **defined **as the ratio of the **weight **of a **given volume** of **aggregate **to the weight of an **equal** **volume **of water.”

**The specific gravity is usually showed the strength and quality of the material. **The specific gravity of **aggregates **test is **usually **used for the **identification **of **stones **or aggregates.

**Aggregates **with **low** **specific gravity **values are mostly **weaker **than those with higher **specific gravity **values.

## Water Absorption

**Water absorption **of aggregates is the % of water absorbed by an **air**–**dried **aggregate when **immersed **in water at **27°C **for a period of **24 hours**.

**Significance of Water Absorption Test On Aggregates**

The water **absorption **test uses to find the **water holding **capacity of the **aggregates**.

The **water **is absorbed by the **aggregates **or **stones **in their pores **known **as **water** **absorption**. Usually, water absorption **gives **an idea about the **strength **of the aggregates. That **aggregate **has more water absorption is **usually unsuitable **for the **construction**.

**There is a basic 3 method specified to find out the specific gravity of aggregates based on their sizes.**

**The aggregates are larger than the 10mm (Basket method)****The aggregates are between 10mm and 40mm (Basket method)**- The aggregates are smaller than 10mm (Pycnometer bottle)

**Read More: Flakiness and Elongation Index Test of Coarse Aggregate**

## Objectives of Specific Gravity and Water Absorption Test

**To Determine the Specific Gravity and Water Absorption Value of Aggregate Sample.**

Reference:- Specific Gravity of Fine Aggregate as per IS Code 2386 (Part 3) – 1963 PDF

**Reference: water absorption test for coarse aggregate is code 2386 (Part 3) – 1963 PDF**

### Apparatus

**1. Balance**

- The
**balance**used to**measure**the**aggregate**has**sufficient capacity**(3kg minimum).**Accuracy**of balance**readable**up to 0.5gm. The**balance**is such a type and its**shape**is also to**permit**the basket**containing**the sample to be**hanging**from the**beam**and**weight**in**water**.

**2. Oven**

The **oven **use for the test is **well ventilated **or **thermostatically** control to **maintain **the **temperature **of **oven** up to **100*C to 110*C.**

**3. Wire Basket**

The **wire basket **used for the test is not more than **6.3mm** **mesh **or it is also a **perforated container **of **convenient size**.

- It usually
**chromium**–**plated**and**done**well**polished**. - It has wire
**hangers**that are not**thicker**than 1mm for**hanging**it from the balance. - A
**basket**has freely**hanged**this type of**watertight**container is**used**. - The dry and
**soft absorbent**clothes are**used**. (2nos.). Min. size of the**clothes**is 75*45cm. - A tray is
**used**for test**Min.**area not less than**650cm^2.** - An
**airtight container**is also used. The**capacity**o container is**similar**to the**basket**.

## Specific Gravity and Water Absorption Test of Aggregates

**Following the procedure used for specific gravity and water absorption test of aggregate,**

**1.** Take about **2 kg of an aggregate sample** (**Aggregate** which has been **artificially heated **shall not be **used**).

**2. **The **aggregates **are **thoroughly **washed so, the finer **particles **of the **dust **are **removed** from their **surface**.

**3.** Then the **washed aggregates** are placed in the **wire basket **and **immersed **in the **distilled **water at a t**emperature between 22° C to 32° C** with cover from the water **surface **at least 5 cm top of the **basket**.

**4.** The **basket immersed** in the water requires **immediate **removal of **entrapped **air. This entrapped air was **removed **by lifting the **basket 25 mm above **the base of the tank and **allowing 25 drops** at the rate of about **1 drop/sec**. Then **basket filled **with **aggregate **is **allowed **to be** immersed **in** water** for a **period of 24 hrs.**

**5.** After **24 hours **the **basket **and the **aggregates** are **weighed **in the **water **at a temperature of **22° C to 32° C**. *(W1)*

**6.** Then the **basket **and the **aggregates **are taken out from the **water **and it allows to drain for a couple of **minutes **after these **aggregates** are **removed **from the basket and **placed **on the **dry cloths**.

** 7.** **After **this the **empty** basket is again **immersed **in the water, apply **25 drops**, and **weighed **in **water**. **(W2)**

**8.** The **aggregates **are placed on the **dry cloth **and **are gently surface dried **with a **cloth** if 1st cloth is not taken **moisture **then **aggregates** are transferred to the second one. **After **these aggregates are spread on the **cloth **and less **exposed **to the **atmosphere away **from direct **sunlight **or also away from the other **source **of the heat until it **appears **to be **completely **surface **dried**.

**10.** For **accelerating **the **unheated** air may be used after the first **10 minutes** for those **aggregates **which are **difficult** to dry and **weigh it. (W3)**

**11**. Then the **aggregates **are placed in the **shallow tray **and put in the **oven **at a **temperature of 100° C to 110° C for 24 hours.**

**12.** **After 24 hours the aggregates are removed** from the oven and fill in the airtight **container** for the **cooling **of it and **weighed**. **(W4)**

**Read More:** **You can download the IS Codes of Aggregates for FREE Here: IS: 2386 (Part I-VII) PDF**

### Observations

**Weight of saturated aggregate sample suspended in wire basket = W1**

**Weight of basket suspended in water = W2**

**Weight of saturating aggregate in water = (W1-W2) = Ws**

**Weight of surface dry aggregate in air = W3**

**Weight of water equal volume of aggregate = (W3 – Ws)**

### Calculation

**Specific Gravity of Aggregate = Dry Wt. Of Aggregate / Wt. Of Equal Volume Water**

= W4 / (W3- Ws)

**Apparent Specific Gravity = Dry. Wt. of Aggregate / Wt. Of the equal volume of water excluding air**

= W4 / (W4-Ws)

**Water Absorption of Aggregate = % by weight of water absorbed in terms of oven-dried weight of aggregate**

= (W3 – W4) x 100) / W4

**Specific gravity and water absorption of a coarse aggregate lab report are prepared after calculating the above values.**

**IS Reccomanded Values**

**The specific gravity of coarse aggregate as per is code is 2.5 to 3.**

**The water absorption of aggregate ranges from 0.1 to 2%.**

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## FAQs:

**Specific Gravity of Coarse aggregate IS Code**

Specific gravity test of coarse aggregate IS Code is** IS 2386-3 (1963): Methods of test for aggregates**

**Specific Gravity of Coarse Aggregate**

The **specific gravity of coarse aggregate** as per is **code** is 2.5 to 3