Evaluation of Resilient Moduli of Pavement Layers at an Instrumented Section on I-35 in Oklahoma

ABSTRACT Resilient Modulus (Mr) is an important material property for pavement design and evaluation. The Mr values can be estimated in the laboratory by measuring material's response under simulated field loading conditions. It can also be determined from nondestructive tests such as the falling weight deflectometer. Some previous studies have shown, however, that the Mr values determined from laboratory testing can differ significantly from that determined from the backcalculated resilient moduli using FWD data. This paper presents the results of a site-specific comparison of the Mr values determined through laboratory testing and backcalculation of FWD data. Both laboratory and FWD data are related to an instrumented pavement section on I-35 in central Oklahoma. Unlike most previous studies that focused on FWD testing on the top of asphalt concrete, in the present study FWD tests are conducted on different layers namely, natural subgrade, stabilized subgrade, aggregate base and asphalt concrete. The study indicated increase in backcalculated Mr values due to the construction of overlying layers. For natural subgrade and aggregate base layer, backcalculated Mr values were found higher than corresponding laboratory determined Mr values. In addition, FWD tests were also performed on top of the asphalt strain gauges and earth pressure cells and strains and pressure data were collected simultaneously. A comparison of the pavement response between the predictions from a multilayer elastic program, KENPAVE, and the in-situ sensors was made.