Air Voids Formula:
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Definition: This calculator determines the percentage of air voids in a material by comparing its theoretical and bulk specific gravities.
Purpose: It helps engineers and construction professionals evaluate material quality and durability, especially in asphalt and concrete mixtures.
The calculator uses the formula:
Where:
Explanation: The difference between theoretical and bulk densities shows the void space, expressed as a percentage of the theoretical maximum density.
Details: Proper air void content is crucial for material durability - too high leads to permeability issues, too low causes rutting and deformation.
Tips: Enter both specific gravity values (Gt should be ≥ Gm). Typical values range from 2.2-2.5 for asphalt mixtures.
Q1: What's a typical air void percentage for asphalt?
A: For asphalt pavements, 3-5% air voids is generally recommended for optimal performance.
Q2: How are the specific gravities measured?
A: Gt is measured on uncompacted samples, while Gm is measured on compacted samples using water displacement methods.
Q3: What if my Gm is higher than Gt?
A: This indicates measurement error as bulk density cannot exceed theoretical maximum density.
Q4: How does air void content affect pavement?
A: Higher voids increase permeability (water damage risk), while lower voids reduce flexibility (cracking risk).
Q5: What's the ideal range for concrete?
A: Concrete typically has 1-3% air voids, with higher percentages (4-8%) for freeze-thaw resistant mixes.