Capacitance-Based Characterization of Air-Void Distribution in Asphalt Mixtures Using a Saturated Reference Field

Area of Science:

• Materials Science
• Civil Engineering
• Geotechnical Engineering

Background:

• Air-void distribution is crucial for asphalt mixture performance, influencing compaction, durability, and permeability.
• Traditional methods offer only average air-void content, failing to capture spatial variations within specimens.
• Understanding air-void distribution is key to ensuring long-term pavement integrity.

Purpose of the Study:

• To develop and validate a capacitance-based method for characterizing vertical and radial air-void distribution in asphalt mixtures.
• To provide a non-destructive, rapid, and cost-effective alternative to conventional air-void testing.
• To enhance the assessment of asphalt mixture quality and pavement performance.

Main Methods:

• Designed and optimized an annular capacitive sensor for cylindrical asphalt specimens.
• Employed a saturated reference field measurement scheme for dielectric indicator derivation.
• Validated vertical distribution with layer-wise measurements and radial distribution with partition-based indicators.

Main Results:

• The capacitance method effectively reflects spatial variations in air voids along specimen height and across radial regions.
• Dielectric indicators accurately characterize non-uniform air-void distribution.
• Robustness confirmed through rotation-angle and saturated-condition stability tests.

Conclusions:

• The saturated reference-field capacitance method offers a powerful tool for analyzing asphalt mixture air-void distribution.
• This approach provides valuable insights into internal structure, aiding in quality control and performance prediction.
• It represents a significant advancement for laboratory assessment of asphalt mixtures.