Technical information

2-18
2.3.3 Falling Weight Deflections
Falling weight deflectometer (FWD) testing was conducted more or less on a monthly
basis at NCAT. These tests were conducted at identical locations within each test
section. The locations themselves were randomly selected at the beginning of the entire
two year experiment. The FWD was a Dynatest 8000 model equipped with seven
sensors spaced at 12 in. (304.8 mm) intervals starting from the center of the load plate.
The load plate had a radius of 300 mm (5.91 in.) and was equipped with a split
configuration to ensure better contact with the pavement surface. For each location, two
drops of about 9,000 lb (4,086 kg) load were executed.
Between November 3, 2003, and February 7, 2005, 135 FWD tests were
conducted on sections N1 and N2 (i.e., 270 drops). The testing locations were later
cored to obtain the as-build pavement thicknesses. The data provided by Table 2.3.7
consists only of those deflections (average of two drops) conducted over a point located
inside the wheel path for which the HMA thickness was verified via coring to be
exactly 5.0 in. (127 mm). It should be noted that the first few deflection bowls
characterize the N1 pavement in its pristine state, soon after construction and before it
had incurred significant damage. Similarly, Table 2.3.8 includes the results for section
N2. Both tables show the HMA temperature at the time of testing measured at a depth
of 50.8 mm (2 in.) from the surface. Also, for preparing both tables the measured
deflections were linearly normalized to a peak load of exactly 9,000 lb (4,086 kg) in
magnitude.