1. What is Effective Asphalt Content?

Definition: Effective asphalt content (AC_e) is the portion of total asphalt in a mix that remains available to coat aggregate particles and contribute to mixture performance.

Purpose: It helps engineers evaluate the actual working asphalt content in hot mix asphalt after accounting for asphalt absorbed by aggregates.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( AC_e \) — Effective asphalt content (%)
• \( AC \) — Total asphalt content (%)
• \( A_a \) — Absorbed asphalt (%)
• \( G_{se} \) — Aggregate effective specific gravity (dimensionless)

Explanation: The formula subtracts the asphalt absorbed by aggregates (adjusted by specific gravity) from the total asphalt content.

3. Importance of Effective Asphalt Content

Details: Proper AC_e ensures adequate asphalt film thickness for durability while preventing excess asphalt that could cause rutting or bleeding.

4. Using the Calculator

Tips: Enter the total asphalt content (%), absorbed asphalt (%), and aggregate specific gravity (default 2.65). All values must be > 0 except absorbed asphalt which can be 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical effective asphalt content range?
A: Typically 3.5-5.5% for dense-graded mixes, but varies by mix design and traffic levels.

Q2: How is absorbed asphalt determined?
A: Through laboratory testing (AASHTO T 84/T 85) measuring aggregate absorption characteristics.

Q3: Why use effective specific gravity?
A: G_se accounts for both impermeable and permeable voids in aggregates that affect asphalt absorption.

Q4: What if my AC_e is too low?
A: Low AC_e may indicate potential durability issues - consider adjusting mix design or using less absorptive aggregates.

Q5: How does this relate to film thickness?
A: AC_e directly influences asphalt film thickness - higher AC_e generally means thicker coating on aggregates.