NCDOT I-40 FWD Joint Testing

North Carolina Department of Transportation selected S&ME to conduct FWD testing at the concrete pavement joint locations along I-40. The project was  part of the I-40 Widening Project between I-440 and NC 42 (approximately twelve miles) in Wake and Johnston Counties, North Carolina.

FWD testing was performed October through November of 2017 in general accordance with ASTM D4694 – 09 and NCDOT procedures. The goal was to collect FWD deflections at the concrete joint locations of I-40 and analyze the deflection data to evaluate the concrete joints load transfer efficiency. Tests were done in eight separate roadway sections, each approximately two-miles long.

S&ME conducted tests in the outside wheel path in the outer-most right through lane of the roadway at every 3-4th concrete slab joint to obtain 140-150 data points per section. S&ME utilized its Dynatest FastFWD because the testing procedure included two seating drops followed by two loading drops targeting 82.1 psi contact pressure under the FWD plate, or approximately 9,000 lb. impact load in the center of the FWD plate. We utilized two FWD geophones located at 0 and 12 inches from the center of the FWD plate as the center of the FWD load plate was located on the approach concrete slab, at 6” away from the tested joint location.

After testing was completed, the raw data was provided to Clark Morrison, P.E., and Shihai Zhang, P.E., with NCDOT Pavement Design Section at the Materials and Tests Unit. The raw data files included, forces, deflections, station ID, and GPS locations. FWD deflections data collected at the concrete joint locations in the eight sections of I-40 was analyzed statistically for load transfer efficiency. A 70% cutoff value of joint load transfer efficiency was used to generate coded map location files. S&ME prepared a final report including tests description, statistical analyses, and location files for NCDOT.