Softening Point Test of Bitumen
(Ring & Ball Method — IS 1205)

Determination of the softening point of bituminous materials using the Ring and Ball apparatus — measuring the temperature at which bitumen softens under load, a key indicator of heat susceptibility.

Overview

What is the Softening Point Test of Bitumen?

The Softening Point Test (Ring and Ball Method) determines the temperature at which a disc of bitumen, held within a horizontal ring, softens and sags downward a distance of 25mm under the weight of a steel ball, when heated at a specified rate in a liquid bath. The softening point indicates the temperature at which bitumen transitions from a solid to a viscous fluid state.

Conducted as per IS 1205 and ASTM D36, the softening point is a mandatory quality parameter for all paving bitumens per IS 73. Higher softening point indicates greater resistance to rutting at high pavement temperatures — critical for roads in hot climates and heavily trafficked highways.

IS 73 Grade Compliance

Results compared against IS 73 minimum softening point for each VG grade.

Precision Temperature Measurement

Digital thermometer with 0.1°C resolution for accurate softening point determination.

Duplicate Testing

Two specimens tested simultaneously per IS 1205 — average reported.

Heat Susceptibility Indicator

Softening point combined with penetration gives Penetration Index (PI) for temperature susceptibility.

NABL Certified Reports

All results on NABL-accredited letterhead per IS 1205 / IS 73.

Complete Bitumen Package

Softening point combined with penetration, ductility and flash point for full QC.

Test in Action

Softening Point Test of Bitumen — Site Images

Ring and Ball Apparatus Setup

Bitumen Disc Sagging 25mm in Bath

Softening Point Temperature Recorded

Test Procedure

How the Softening Point Test of Bitumen is Conducted

1

Sample Preparation

Bitumen heated to pouring temperature. Rings placed on brass plate and filled slightly overfull. Cooled at room temperature, then trimmed flush.
2

Bath Setup

Rings with bitumen discs placed on support in glass vessel. Steel balls (3.5g) centred on bitumen discs using guide.
3

Heating Rate

Bath liquid (water or glycerin depending on expected softening point) heated at 5°C/min per IS 1205.
4

Softening Point Recording

Temperature recorded when each bitumen disc sags 25mm and touches bottom plate. Average of two readings taken.
5

IS 73 Compliance Report

Softening point vs IS 73 VG grade minimum (54°C for VG 30, 47°C for VG 10). NABL report within 3 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 1205	Methods for Testing Tar and Bituminous Materials — Determination of Softening Point	Softening Point	Indian Standard
IS 73	Paving Bitumen — Specification	Bitumen Grades	Indian Standard
ASTM D36	Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)	Softening Point	ASTM
MORTH	Specifications for Road and Bridge Works — Clause 500	Bitumen Spec	MORTH

Applications

Where is the CAPO Test Used?

Grade verification of paving bitumen at hot mix plant acceptance

High-temperature rutting resistance assessment for heavy traffic roads

PMB and CRMB modified bitumen softening point verification

Bitumen quality monitoring during extended storage periods

Forensic investigation of pavement rutting and bitumen grade mismatch

Research on bitumen aging and temperature susceptibility

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid IS 73 grade certificates for NHAI and MORTH projects.

Digital Temperature Precision0.1°C resolution thermometer for accurate, reproducible results.

Complete Bitumen PackageSoftening point + Penetration + Ductility + Flash Point offered together.

Fast 3-Day TurnaroundResults within 3 working days.

Pan-India CoverageBitumen testing at all 7 lab locations.

Penetration Index CalculationPI calculated from softening point and penetration for temperature susceptibility assessment.

Softening Point Test of Bitumen(Ring & Ball Method — IS 1205)