Atterberg Limits Test

Atterberg Limits Test
(Liquid Limit, Plastic Limit & Plasticity Index)

Laboratory determination of liquid limit, plastic limit and plasticity index of fine-grained soils per IS 2720 Part 5 — essential for soil classification, compressibility assessment and foundation design.

Overview

What is the Atterberg Limits Test?

Atterberg Limits define the water content boundaries between different consistency states of fine-grained soils. The Liquid Limit (LL) is the water content at which soil transitions from plastic to liquid state, measured by Casagrande's cup or cone penetrometer method. The Plastic Limit (PL) is the lowest water content at which soil can be rolled into a 3mm thread without crumbling. The Plasticity Index (PI = LL − PL) indicates the range of water content over which the soil remains plastic.

Conducted as per IS 2720 Part 5, Atterberg limits are the most fundamental soil classification tests — used in the IS 1498 soil classification system, Casagrande plasticity chart, and as key inputs for compressibility estimation (using correlations with CC, CV), swelling potential assessment and subgrade CBR correlation. Global Lab uses both Casagrande apparatus (percussion method) and cone penetrometer (fall cone) for liquid limit determination.

Liquid Limit — Two Methods

Casagrande percussion cup (IS 2720 Part 5) and cone penetrometer (fall cone) methods both available.

Plastic Limit by Thread Method

3mm thread rolling at standard rate — PL determined per IS 2720 Part 5.

Plasticity Index (PI = LL − PL)

PI classifies soil as non-plastic, low, medium, high or very high plasticity per IS 1498.

IS 1498 Soil Classification

LL and PI plotted on Casagrande chart — CL, CH, CI, ML, MH, OL, OH classification.

NABL Certified Reports

All test and calibration results are backed by traceable measurements and standardized procedures.

Shrinkage Limit Available

Shrinkage limit per IS 2720 Part 6 available as an add-on test.

Test in Action

Atterberg Limits Test — Site Images

Casagrande Liquid Limit Apparatus — Groove Cut in Soil

Plastic Limit Thread Rolling Test — 3mm Diameter

IS 1498 Plasticity Chart — CL/CH/CI Classification

Test Procedure

How the Atterberg Limits Test is Conducted

1

Sample Preparation

Soil sieved through 425μm. Sufficient water added to bring to slightly above liquid limit consistency. Mixed thoroughly and allowed to stand 24 hours.
2

Liquid Limit Test

Soil placed in Casagrande cup. Standard groove cut. Cup dropped 25mm. LL = water content at 25 blows (interpolated from flow curve of 4 tests).
3

Plastic Limit Test

Soil rolled on glass plate into 3mm diameter thread. PL = water content at which thread just crumbles.
4

Calculations

PI = LL − PL. Liquidity Index = (w − PL)/PI. Activity = PI / (% clay fraction).
5

IS 1498 Classification & Report

LL and PI plotted on Casagrande plasticity chart. Soil classified per IS 1498. NABL report within 3 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 2720 Part 5	Methods of Test for Soils — Determination of Liquid and Plastic Limit	Atterberg Limits	Indian Standard
IS 1498	Classification and Identification of Soils for General Engineering Purposes	Soil Classification	Indian Standard
IS 2720 Part 6	Methods of Test for Soils — Determination of Shrinkage Factors	Shrinkage Limit	Indian Standard
ASTM D4318	Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils	Atterberg Limits	ASTM

Applications

Where is the Atterberg Limits Test Used?

Soil classification for site investigation reports on all civil engineering projects

Subgrade soil quality assessment for highway design per IRC and MORTH

Foundation soil compressibility and consolidation settlement estimation

Expansive soil swelling potential assessment combined with FSI

Embankment fill material classification and compaction specification

Pavement subgrade strength correlation and CBR prediction from plasticity data

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid IS 2720 Part 5 certificates for all geotechnical reports.

Both LL Methods AvailableCasagrande cup and fall cone penetrometer — international comparability.

IS 1498 Classification ProvidedCasagrande chart classification (CL/CH/CI/ML/MH) included in every report.

Fast 3-Day ReportComplete Atterberg limits and NABL report within 3 working days.

Pan-India CoverageGeotechnical lab at all 7 NABL-accredited locations.

Combined Soil PackageAtterberg + PSD + Compaction + FSI + Specific gravity as complete characterisation.

Atterberg Limits Test(Liquid Limit, Plastic Limit & Plasticity Index)