Design Model for Reflection Cracking in Airport Asphalt Overlays (Phase II)
📨 Principal Investigator: Hasan Ozer
🔖 Co-PI: Imad L. Al-Qadi, Carlos Armando Duarte
🤝 Sponsor: Federal Aviation Administration (FAA)
📅 Timeline: 2025 – Ongoing
Highlights
Introduction
The Phase I study established that reflective cracking in airport asphalt overlays can be simulated with high fidelity using 3-D fracture mechanics and viscoelastic material models, a significant milestone. But translating that simulation capability into a design tool that an airport engineer can actually use in daily practice requires more than accurate crack propagation calculations. It requires a way to connect those calculations to observable field outcomes: what percentage of joints will show cracking after a given number of years? How severe will those cracks be? And when does the cracking become severe enough to constitute structural failure of the overlay? These questions belong to the domain of transfer functions, the mathematical bridges that connect mechanistic model outputs to field performance observations.
The FAA’s long-range goal for its Reflective Cracking Study Program has always been to develop fully validated transfer functions and implement them in FAARFIELD, the agency’s official pavement design software used at airports nationwide. Phase II of this research program responds to that goal directly.
Methodology and Framework
The proposed research is organized around three parallel tracks. The first track focuses on building the validation and calibration infrastructure: developing a large and diverse airport pavement condition database by collecting distress surveys, traffic records, and climate data from over 100 airports across the United States in diverse climatic regions. This database will be used to calibrate transfer functions by matching computational damage predictions to observed field cracking progression. The second track advances computational models by adding two new capabilities not included in Phase I: the simulation of AC-PCC interface debonding and load transfer efficiency (LTE) between adjacent concrete.
The third track develops the complete mechanistic-empirical design framework, connecting all components into a design protocol suitable for FAARFIELD implementation. The M-E framework processes monthly traffic and climate inputs, calculates the viscoelastic energy release rate via ANN surrogate models and EVCP, applies the modified Paris Law to accumulate crack growth incrementally, and ultimately predicts the percentage of cracked joints as a function of overlay age using S-shaped transfer functions calibrated to field data. The iterative design protocol evaluates trial overlay thicknesses against a cumulative damage factor (CDF) failure criterion, allowing engineers to select the minimum overlay thickness that meets the desired service life.
