Correlation of non-destructive pavement test devices

The Dynaflect has been the standard tool for non-destructive testing (NDT) within the New Brunswick Department of Transportation since 1971. The Dynaflect applies a dynamic load varying sinusoidally from 6.8 kN to 11.2 kN at a frequency of 8 hertz. This load is approximately one tenth of the dual tire load of an Equivalent Single Axle Load (ESAL) used in pavement damage calculations. The Falling-Weight Deflectometer (FWD) has become the preferred tool for NDT with a typical load in the range of 40 kN under an impact equivalent to a frequency of 33 hertz.;Most of the overlay calculations in Canadian provinces are based on conversion of either the Dynaflect or FWD to an equivalent Benkelman Beam rebound. Several overlay design methods have been developed to use the additional information provided by the multiple sensors of the standard FWD. Similar methods are not widely available for the older Dynaflect. This project considers the possibility of developing correlation relationships between the Dynaflect and FWD to permit the use of FWD style overlay calculations using the older Dynaflect technology.;This study included the data from several New Brunswick highways with both FWD and the Dynaflect testing carried out on the same day. Regression analysis of the first five sensors of the FWD with the corresponding Dynaflect sensors produced overall equations with highly significant slopes and correlation coefficients (R2) in the range of 0.80 to 0.91. Some potential methods of using Dynaflect deflections converted to FWD deflections in overlay design calculations are explored as alternatives to the relatively dated Benkelman Beam overlay design charts.