IS 2720:1980 Part 3 is the Indian Standard (BIS) for methods of test for soils: part 3 determination of specific gravity. This standard specifies the laboratory methods for determining the specific gravity of soil solids. It covers procedures for both fine-grained soils (using a pycnometer or density bottle) and coarse-grained soils (using a gas jar). This fundamental soil property is essential for calculating phase relationships like void ratio and degree of saturation.
Specifies methods for determining the specific gravity of soil particles, applicable to both fine-grained and coarse-grained soils.
Overview
- Status
- Current
- Usage level
- Essential
- Domain
- Geotechnical — Roads and Pavement
- Type
- Testing Method
Also on InfraLens for IS 2720
Practical Notes
! Complete removal of entrapped air by vacuum is the most critical step; insufficient de-airing leads to erroneously low specific gravity values.
! Applying the temperature correction factor (Kt from Table 1) to normalize the result to the standard 27°C is mandatory for reporting.
! The code is split into two sections within Part 3: Section 1 for fine-grained soils and Section 2 for coarse-grained soils, which require different apparatus sizes and sample quantities.
Frequently referenced clauses
soilfine grained soilcoarse grained soil
International Equivalents
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Key Values6
Quick Reference Values
Standard reporting temperature27 °C
Accuracy of weighing balance0.001 g for fine-grained soils
Pycnometer/Density Bottle capacity50 ml for fine-grained soils
Typical G for sand (inorganic)2.65 - 2.68
Typical G for clay (inorganic)2.70 - 2.80
Minimum mass of soil for fine-grained soil test25 to 50 g
Key Formulas
G = (M2 - M1) / [ (M4 - M1) - (M3 - M2) ] — Specific Gravity at test temperature T°C
G_27°C = Kt * G_T°C — Specific Gravity corrected to standard temperature 27°C
Tables & Referenced Sections
Key Tables
Table 1 - Temperature Correction Factor Kt
Key Clauses
Clause 3 - Apparatus (Lists pycnometer, density bottle, vacuum source etc.)
Clause 4 - Procedure (General steps for the test)
Clause 8 - Calculations (Formula for determining specific gravity)
Section 1 - Determination of specific gravity of fine-grained soils
Section 2 - Determination of specific gravity of coarse-grained soils
Frequently Asked Questions4
What is the standard temperature for reporting specific gravity?+
The specific gravity is reported at a standard temperature of 27°C, after applying a temperature correction factor (Clause 8.2).
Why is a vacuum source needed for the specific gravity test?+
A vacuum is used to remove all entrapped air bubbles from the soil and water slurry. Air bubbles occupy volume and would cause the calculated specific gravity to be inaccurately low.
What is the difference between Part 3 / Section 1 and Section 2?+
Section 1 covers the test for fine-grained soils using a small pycnometer or density bottle. Section 2 is for coarse-grained soils (particles larger than 4.75 mm) and requires a larger gas jar and sample size.
What does an unusually low specific gravity value indicate?+
A value significantly below 2.60 may indicate the presence of organic matter in the soil or testing errors, such as incomplete de-airing.