CHARACTERIZATION OF RUBBLIZED CONCRETE AIRPORT PAVEMENTS AT THE NAPTF USING NON-DESTRUCTIVE TESTING METHODS

At the Federal Aviation Administration’s (FAA) National Airport Pavement Test Facility (NAPTF), three rigid airport pavements (MRC, MRG, and MRS) with 12-inch thick concrete slabs on different support systems (slab on crushed stone base, slab on grade, and slab on stabilized base) were trafficked to complete failure using dual tandem (B-747) and triple dual tandem (B-777) landing gear configurations. All three test items were constructed on CBR 7 subgrade (DuPont clay). Test item MRC consisted of 12-inch concrete slabs over 10-inches of crushed stone subbase, MRG consisted of 12-inch concrete slabs over subgrade, and MRS consisted of 12-inch concrete slabs over a 6-inch econocrete subbase. The north sides of the test items were rubblized with a resonant pavement breaker. After rubblization, the rubblized concrete was rolled and paved with a 5-inch thick HMA (hot mix asphalt) overlay. The overlaid pavements were subjected to full-scale accelerated traffic tests under the 4-wheel landing gear configuration (with wander) and 55,000-lbs wheel load. No significant distresses were observed for 5000 passes after which the wheel load was increased to 65,000-lbs and 6-wheel landing gear was used for testing. Heavy-weight deflectometer (HWD) tests were routinely performed using FAA’s KUAB HWD equipment three different load levels – 12,000, 24,000, and 36,000 lbs. Portable Seismic Pavement Analyzer (PSPA) was used in conjunction with the HWD to estimate the asphalt concrete modulus. Moduli for the rubblized concrete layer were backcalculated using FAA’s BAKFAA software. This paper summarizes the pavement structure uniformity within a given test item from HWD tests, and changes in the modulus of rubblized concrete layer with deterioration in pavement structure backcalculated using BAKFAA. Pavement performance during the traffic tests is also described.