Evaluation of the Influence of Asphalt Concrete Pavement Discontinuities on Falling Weight Deflectometer Measurements

The influence of cracks is a major concern for interpretation of the deflection basin obtained from FWD tests. In order to give a better insight of the role of longitudinal and transverse cracks on FWD measurements, an exhaustive FWD campaign was conducted on a recently rehabilitated flexible pavement. FWD tests were done on a selected uncracked pavement section in order to obtain reference values of the deflection basin. Subsequently, cracks were cut into the 100mm thick asphalt concrete layer and FWD tests were conducted close to a transverse crack as well as a longitudinal crack. The asphalt concrete layer temperature was monitored during deflection tests for temperature correction purposes. As expected, the mean temperature of the asphalt concrete layer has a major influence on the deflections measured from the geophones close to the loading plate, and field data must be corrected accordingly. The comparison between FWD test data before and after cracking shows that a transverse crack creates a distortion in the shape of the deflection basin when the loading plate is near the crack. In the case of the longitudinal crack, an increase in the value of deflection was noted for the first geophones when the loading plate is near the crack. It was established that the influence of any crack on deflections was negligible if the distance of the loading plate with respect to the crack was larger than 600 mm in pavements with a relatively thin wearing course. For the covering abstract see ITRD E118503.