Stiffness Characterization With Falling Weight Deflectometer in Accelerated Pavement Testing

As part of a study that evaluates the reflective cracking performance of asphalt mixes used as overlays for rehabilitating cracked asphalt concrete pavement, 6 test sections were built and tested with heavy vehicle simulator (HVS) at Richmond Field Station of the University of California Pavement Research Center. The HVS testing lasted for about 6 years. This paper analyzes and summarizes the falling weight deflectometer (FWD) test conducted on the test sections during the whole period. The purpose of the paper is to characterize the HVS sections with FWD, compare trafficked and untrafficked stiffness change, detect aging and seasonal effects on mix stiffness, and compare the stiffness backcalculated from FWD test with that measured in the laboratory. CalBack, a backcalculation program developed for California Department of Transportation, was used. It was found that the modulus of aggregate base was generally positively correlated with the moduli of asphalt concrete and subgrade; aging of asphalt concrete was apparent in most sections. One to 3 years after HVS testing, the modulus of damaged asphalt concrete generally recovered to some extent on most sections. The moduli of asphalt concrete backcalculated from overlay sections match reasonably well with the moduli measured in the laboratory by the frequency sweep test on flexural beam specimens.