Detection of Delamination in the HMA Layer of Runway Pavement Structure Using Asphalt Strain Gauges

Asphalt pavement distresses like surface shoving and slippage cracking can be found at airports in areas where aircraft brake and turn, such as high-speed exits, as a result of the high surface-shear forces. Slippage failure is typically caused by the deterioration of bonding between asphalt layers (delamination), or a lack of shear resistivity within the surface-layer asphalt mix. High pavement temperatures have also been shown to contribute to slippage failures in asphalt concrete pavements. At the intersection of Runway 4 R-22 L and High-Speed Taxiway N (HST-N) at Newark Liberty International Airport (EWR), interlayer delamination was determined to be the cause of shoving and slippage cracking on the pavement surface. In 2012, asphalt strain gauges were installed during a scheduled repaving of the runway and taxiway. This paper details the components of an asphalt strain gauge instrumentation system, and analyzes the strain responses collected from the gauges installed at EWR. By identifying large discrepancies in strain responses between strain gauges installed in the hot mix asphalt (HMA) overlay and lower layers of asphalt pavement (HMA milled surface), areas of potential delamination were identified. Delamination was successfully detected by the instrumentation and is shown to increase in severity over time, especially in the gauges nearest to the taxiway lead-line (centerline). Strain responses are also affected by temperature at the interface and aircraft speed. Photographs of the taxiway surface taken in the summer of 2014 confirm that slippage distress is occurring in the same areas in which the strain gauges indicate delamination. Statistical analysis methods were employed, and the Difference between Means tests and Kolmogorov-Smirnov Tests confirm that the measurement of $\mathrm{\Delta }$ strain ($\mathrm{\Delta }\epsilon$) was significantly distinct for bonded versus delaminated pavements.