Loss on Heating Test of Bitumen
(Thin Film Oven Test — IS 9381)

Assessment of bitumen aging susceptibility by measuring percentage loss in mass after heating a thin film at 163°C for 5 hours — simulating the aging that occurs during hot mix plant production.

Overview

What is the Loss on Heating Test of Bitumen?

The Loss on Heating Test (Thin Film Oven Test — TFOT) measures the percentage change in mass of a thin film of bitumen after oven heating at 163°C for 5 hours. The mass loss indicates volatilisation of lighter fractions — representing the aging that occurs when bitumen is heated and mixed at the hot mix plant.

Conducted as per IS 9381 and ASTM D1754, the loss on heating test determines bitumen heat stability and the degree of aging during mixing. Low mass loss (≤1% for VG grades per IS 73) indicates good heat stability. Residual penetration after heating confirms the bitumen has not aged excessively during plant mixing.

IS 73 Mass Loss Limit

≤1% mass loss for VG grade paving bitumens per IS 73.

Oven Aging Simulation

163°C / 5 hours TFOT simulates aging during hot mix plant mixing.

Residual Penetration

Penetration of residue measured to assess degree of hardening after aging.

Thin Film Geometry

50g bitumen in 325mm dia flat container — standardised thin film per IS 9381.

NABL Certified Reports

All results on NABL-accredited letterhead per IS 9381 / IS 73.

Aging Index

Ratio of residual penetration to original penetration quantifies aging severity.

Test in Action

Loss on Heating Test of Bitumen — Site Images

Bitumen Film Dish Before TFOT

Thin Film Oven at 163°C

Mass Loss Percentage Calculated

Test Procedure

How the Loss on Heating Test of Bitumen is Conducted

1

Sample Preparation

50g bitumen poured into standard flat dish (325mm dia, 9.5mm depth). Cooled to room temperature.
2

TFOT Oven Placement

Flat dishes placed on rotating shelf in oven at 163±1°C. Shelf rotates at 5–6 rpm for even heating.
3

5-Hour Aging

Samples heated at 163°C for exactly 5 hours per IS 9381 / ASTM D1754.
4

Mass Loss Calculation

Dishes weighed before and after heating. Mass loss percentage = (initial − final) / initial × 100.
5

Residual Penetration & Report

Penetration tested on aged residue. Aging index calculated. IS 73 compliance reported. NABL report within 3 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 9381	Methods for Testing Tar and Bituminous Materials — Determination of Loss on Heating	Loss on Heating	Indian Standard
IS 73	Paving Bitumen — Specification	Bitumen Grades	Indian Standard
ASTM D1754	Standard Test Method for Effects of Heat and Air on Asphaltic Materials (Thin-Film Oven Test)	TFOT	ASTM
ASTM D2872	Standard Test Method for Effect of Heat and Air on a Moving Film of Asphalt (RTFOT)	RTFOT	ASTM

Applications

Where is the CAPO Test Used?

IS 73 grade acceptance testing for all paving bitumen tanker deliveries

Assessment of bitumen heat stability for high-temperature hot mix plants

Aging susceptibility evaluation for bitumen storage at elevated temperatures

PMB and CRMB aging resistance assessment

Research on bitumen aging and long-term pavement performance prediction

Quality audit of bitumen from different refineries and suppliers

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid IS 73 loss on heating certificates for NHAI projects.

Aging Index ReportingResidual penetration and aging index reported alongside mass loss.

Complete Bitumen PackageLoss on heating + Penetration + Softening point + Ductility offered together.

Fast 3-Day TurnaroundResults within 3 working days.

Pan-India CoverageTesting at all 7 lab locations.

RTFOT Also AvailableRolling Thin Film Oven Test (ASTM D2872) available for Superpave mix design.

Loss on Heating Test of Bitumen(Thin Film Oven Test — IS 9381)