Ductility Test of Bitumen
(Bitumen Ductility — IS 1208)
Measurement of the ductility of bituminous materials by stretching a standard briquette specimen at 27°C until failure — a key quality indicator for bitumen cohesion and resistance to cracking.
What is the Ductility Test of Bitumen?
The Ductility Test of Bitumen measures the distance in centimetres to which a standard briquette of bitumen can be stretched at 27°C at a rate of 50mm/min before the thread breaks. Ductility indicates the cohesive property of bitumen — high ductility means good bitumen film continuity and resistance to cracking under traffic and temperature cycling.
Conducted as per IS 1208 and ASTM D113, ductility is a mandatory quality parameter for all paving bitumens per IS 73. Minimum ductility of 75 cm is required for VG 10 and VG 20, and 50 cm for VG 30 and VG 40 grades. Global Lab maintains a temperature-controlled ductility testing bath at 27±0.5°C for accurate testing.
Ductility Test of Bitumen — Site Images
How the Ductility Test of Bitumen is Conducted
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1Sample PreparationBitumen sample heated to pouring temperature (80–90°C). Briquette mould placed on brass plate greased with glycerin/talc mixture.
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2Briquette CastingMelted bitumen poured into briquette mould slightly overfilled. Cooled at room temperature for 30 minutes, then in water bath at 27°C for 90 minutes.
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3Mould Removal & LevellingSide pieces removed. Excess bitumen trimmed flush with straight edge. Briquette transferred to ductility machine clips.
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4Ductility TestMachine pulls briquette at 50mm/min at 27±0.5°C until thread breaks. Distance stretched is recorded.
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5Result & IS 73 ComplianceAverage of 3 results reported in cm. Compared against IS 73 Table 1 minimum. NABL report within 3 days.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| IS 1208 | Methods for Testing Tar and Bituminous Materials — Determination of Ductility | Ductility Test | Indian Standard |
| IS 73 | Paving Bitumen — Specification | Bitumen Grades | Indian Standard |
| ASTM D113 | Standard Test Method for Ductility of Asphalt Materials | Ductility | ASTM |
| MORTH | Specifications for Road and Bridge Works — Clause 500 | Bitumen Spec | MORTH |