Factors Affecting Portable Falling Weight Deflectometer Measurements

Lower cost and better quality evaluations of pavement characteristics require precise quality assurance/control programs that relate test results to design practice. Rapid in situ stiffness testing enables transportation agencies to conduct reliable and defensible quality assurance programs. This study explores the feasibility of using a portable falling weight deflectometer (PFWD) to characterize pavement layer moduli. Efforts were made to investigate factors that may influence PFWD results. Field dynamic cone penetrometer as well as laboratory California bearing ratio tests were performed and compared with results obtained from PFWD. One of the most important factors concerning the PFWD modulus is the size of the PFWD loading plate. Our testing suggests that an appropriate plate size can be chosen from the measured modulus. The effects of drop height on PFWD moduli were found to be small as the moduli remained about the same regardless of the drop heights. Considering the personnel and skills required for data collection, result interpretation, speed of testing, and the quality of data produced, the PFWD is preferred. PFWD is an ideal device for quality control during compaction monitoring because it enables a rapid stiffness assessment of individual pavement layers.