Comparison between laboratory investigation and non-destructive testing methods for mechanistic characterization of asphalt pavements

Layer thickness and material modulus are indispensable parameters in pavement evaluation. Two approaches to obtain those parameters were compared. The first method was by coring from the pavement to obtain material samples and testing them in the laboratory. The second method was by non-destructive testing (NDT), consisting of using mechanical and electronic devices to measure the pavement response under applied loads on the pavement surface and deduce the thickness and moduli of pavement system.;Falling weight deflectometer (FWD), ground penetrating radar (GPR) and spectral analysis of surface wave (SASW) were used for the on-site pavement test and measurement. The combination of these devices not only gave accurate measurements, but also provided confirmation of the results because two test devices were used for each measured parameter. An experimental design method was used in planning and selecting pavement sections to guarantee the representative nature of the pavements and to rule out possible bias of the data source. Three back-calculation software systems, ELMOD, EVERCALC and MODULUS, were used to calculate the layer moduli of pavement structures. Cored samples from the same test points as those tested by NDT were analyzed in the laboratory under several temperatures, load levels and load frequencies. Statistical tools were used in deriving the conversion equations relating thickness and layer moduli from NDT to those from laboratory tests.;The study concludes that excellent agreement exists between the radar detected thickness and core thickness. The true thickness at a given point can be predicted from radar detection without significant effect on the accuracy of thickness analysis and back calculated modulus. There is very good linear relationship between the back-calculated asphalt concrete (AC) modulus and laboratory tested dynamic modulus. The agreement between the modulus from FWD and SASW is marginal. In terms of layer thickness and modulus back-calculation, the radar and FWD test can replace the coring and laboratory testing in pavement evaluation without significant negative effect on the accuracy of evaluation.