Testing Gilsonite-Modified Asphalt Binder in the Lab

Before using gilsonite on a paving project, the modified binder should be tested to confirm the target properties.

Sample preparation

Heat the base bitumen to 170–180°C, add the planned percentage of gilsonite powder and stir with a laboratory mixer until fully dissolved (usually 30–60 minutes). Check for undissolved particles on a glass slide.

Conventional tests

• Penetration at 25°C (ASTM D5 / EN 1426) – drops as gilsonite content rises
• Softening point (ASTM D36 / EN 1427) – rises with gilsonite content
• Rotational viscosity at 135°C (ASTM D4402) – confirms pumpability and helps set mixing temperature
• Ductility – usually decreases with higher gilsonite content

Performance-grade tests

• DSR on original and RTFO-aged binder for the high-temperature grade
• BBR on PAV-aged binder for the low-temperature grade
• MSCR for rutting resistance under heavy traffic

Building a dosage curve

Test at least three gilsonite contents (for example 4%, 8% and 12%) and plot softening point, penetration and PG high temperature against dosage. Select the lowest dosage that meets the specification.

Storage stability

Gilsonite dissolves in bitumen, so separation is normally low, but a storage stability (tube) test is still recommended for terminal blends.

Order lab samples of asphalt modifier grade gilsonite and read gilsonite and PG grades.