Review of Lightweight Deflectometer for Routine in Situ Assessment of Pavement Material Stiffness

Abstract

The use of a portable lightweight deflectometer (LWD) for construction quality control or material investigation for earthworks and road construction is increasing around the world. LWD is reviewed as a field evaluation tool, the test variables and data quality are discussed, and the usefulness and limitations for a variety of earthwork and road assessment scenarios are described. A state-of-the-art reference document is provided for LWD users, consultants, material specifiers, contractors, and clients. Data from road foundations (subgrades, granular capping, and subbase) and fully constructed in-service (thinly surfaced) roads were reviewed to demonstrate the flexibility of the LWD and to show that its determination of stiffness modulus may differ from that of the conventional falling weight deflectometer to a varying extent. A series of laboratory investigations was undertaken to demonstrate the sensitivity to uniformity of plate-surface contact and the limitations in the interpretation of peak displacement from the device. A good understanding of the device workings and careful specification of the test variables are required both to analyze the data correctly and to permit comparison between data sets. It is concluded that the device is a useful and versatile field quality control and pavement investigation tool if an understanding of the device issues is considered by data users.