1. What is Asphalt Film Thickness?

Definition: The thickness of the asphalt binder coating around aggregate particles in an asphalt mixture.

Purpose: A key parameter in asphalt mix design that affects durability, aging resistance, and performance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( AFT \) — Asphalt film thickness (inches)
• \( V_b \) — Binder volume (cubic feet)
• \( A \) — Surface area of aggregates (square feet)

Explanation: The binder volume is divided by the total surface area of aggregates to determine the average thickness of the asphalt coating.

3. Importance of Asphalt Film Thickness

Details: Proper film thickness ensures adequate coating of aggregates, durability against traffic loads, and resistance to moisture damage and aging.

4. Using the Calculator

Tips: Enter the binder volume in cubic feet and the surface area of aggregates in square feet. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical AFT value?
A: Optimal AFT ranges between 8-15 microns (0.0003-0.0006 inches) for most asphalt mixes.

Q2: How do I find the binder volume?
A: Calculate from asphalt content percentage and mix volume, or use lab test results.

Q3: How is surface area determined?
A: Typically calculated based on aggregate gradation and specific surface area factors.

Q4: Why is AFT important for mix design?
A: Too thin film leads to brittle mixes, while too thick film causes rutting and bleeding.

Q5: Does temperature affect AFT?
A: Yes, higher temperatures reduce effective film thickness as binder becomes less viscous.