Pycnometer Test of Aggregate | Specific Gravity Test of Aggregate | Specific Gravity and Water Absorption Test of Aggregate (For Aggregate Smaller than 10 mm)

The Pycnometer Test of Aggregate is one of the three main methods specified in the Indian standard code for the calculation of Specific Gravity and Water Absorption of Aggregate.

The pycnometer test of aggregate is also known as method III in the Indian standard code.

The methods are according to different sizes of aggregate.

Method I – The aggregate is large than 10 mm.

Method II – The aggregate is between 40 mm to 10 mm.

Method III – The aggregate is smaller than 10 mm.

Hence, the pycnometer test is usually used to find specific gravity and water absorption of fine aggregte which are smaller than 10 mm.

Aim of Specific Gravity and Water Absorption Test of Aggregate

The aim of this test is to determine,

• Specific gravity of aggregate
• Apparent specific gravity of aggregate
• Water absorption of aggregate

Importance of Specific Gravity Test of Aggregate

The significance of specific gravity test for aggregate is as given below.

Specific Gravity Test of Aggregate

• Helps in evaluating the quality and properties of aggregates.
• Provides information about the strength and durability of the material.
• Assists in proportioning concrete mixes to achieve the desired strength.
• Aids in evaluating the suitability of aggregates for various construction applications.

Water Absorption Test of Aggregate

• Indicates the porosity of aggregates.
• Affects the workability and moisture content of concrete.
• Impacts the durability of concrete, especially in freeze-thaw environments.
• Assists in determining the appropriate amount of water to be added to concrete mixes.

To understand the significance of specific gravity of aggregate in detail – CLICK HERE.

Is Code for Specific Gravity Test of Aggregate

IS 2386 (Part 3) – 1963

IS 2386 – Methods of Test for Aggregates for Concrete

Part 3 – Specific Gravity, Density, Voids, Absorption, and Bulking

Apparatus For Pycnometer Test of Aggregate (For Aggregate Smaller than 10 mm)

The apparatus for specific gravity and water absorption test of aggregate or pycnometer test shall consist of,

1. Balance

The balance shall be of,

• Capacity – > 3 kg
• Accuracy and readability – 0.5 g

2. Oven

The oven shall be,

• Well ventilated
• Thermostatically controlled
• Able to maintain a temperature of 100 to 110 ℃

3. Pycnometer

It is a vessel as shown in the picture below.

4. Instrument for supplying a current of warm air

For example, a hair dryer

5. Tray

Area of the tray – > 325 cm²

6. Airtight container

Capacity – Large enough to contain the sample

7. Filter papers and funnel.

Sample for Pycnometer Test of Aggregate

The sample shall be as required below,

a. For the aggregate of size 10 mm to 4.75 mm,

Sample weight – 1 kg

b. For the aggregate of size finer than 4.75 mm,

Sample weight – 500 g

Specific Gravity of Aggregate Test / Pycnometer Test Procedure

The procedure for this test is as follows,

• Place the sample in a tray and cover it with distilled water at a temperature of 22 to 32°C.
• Remove the air entrapped in the sample or bubbles on the surface of the aggregate through gentle agitation by using a rod.
• Keep the sample immersed for 24 ± 1/2 hours.
• Carefully drain the water from the sample by decantation through a filter paper and return any retained material to the sample.
• Expose the aggregate, including the retained solid matter on the filter paper, to a gentle current of warm air to evaporate surface moisture.
• Stir the sample at frequent intervals to ensure uniform drying until no free surface moisture is visible and the material attains a “free-running” condition.
• Weigh the saturated and surface-dry sample (weight A).
• Transfer the aggregate to a pycnometer and fill it with distilled water.
• Remove any trapped air by rotating the pycnometer on its side, covering the hole in the cone apex with a finger.
• Top up the pycnometer with distilled water to remove any froth from the surface and to make the water surface flat in the hole.
• Dry the pycnometer on the outside and weigh it (weight B).
• Empty the pycnometer contents into the tray.
• Ensure that all the aggregate is transferred.
• Refill the pycnometer with distilled water to the previous level, dry it on the outside, and weigh it (weight C).
• Ensure the temperature difference of the water in the pycnometer during the first and second weighing does not exceed 2°C.
• Carefully drain the water from the sample by decantation through filter paper and return any retained material to the sample.
• Place the sample in a tray and put it in the oven at a temperature of 100 to 110°C for 24 ± 1/2 hours, occasionally stirring to aid drying.
• Cool the sample in an airtight container and weigh it (weight D).
• Perform this test twice.

Calculations for Specific Gravity and Water Absorption Test of Aggregate (For Aggregate Smaller than 10 mm)

Calculations for specific gravity, apparent specific gravity, and water absorption of aggregate are given below.

Specific gravity = D/A-(B-C)

Apparent specific gravity = D/D-(B-C)

Water absorption (percent of dry weight) = 100(A-D)/D

Where,

A = Weight in g of saturated surface-dry sample

B = Weight in g of pycnometer containing the sample and filled with distilled water

C = Weight in g of pycnometer filled with distilled water only

D = Weight in g of oven-dried sample

Reporting of the Result of the Test

Below details are to be noted in the results.

• Individual and mean results
• Grading of the aggregate

Pycnometer Test of Aggregate at A Glance

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