FWD Testing as a Construction Control Tool

Abstract

Construction control is an important link in the construction process chain. It serves as a quality control means, but also assures that the builder fulfills the contract. Various ways of performing control have evolved over time, many employing statistical methods. Apart from taking samples to be analyzed in the laboratory, field tests are done to check for compaction or density and properties like elastic modulus. The latter could also be utilized in the mechanistic design process to either test, or suggest alterations to, the initial design. In comparing derived moduli from e.g. plate loading tests with Falling Weight Deflectometer (FWD), results have been inconclusive. For one thing the time domain is different, but also the magnitude of the load. The present paper presents some comparative tests with static plate tests with light and heavy FWD data. The latter can produce a similar load to the one exerted by traffic, so that appropriate moduli can be used in the design model. For testing compaction, repeated loading and stress sensitivity analyses can be used, which are described in the paper. For testing on subgrade materials there are some practical problems like accessibility and uneven surfaces that must be coped with if heavier equipment is being used. However, as the data can indeed be used for active design, it is viable to do the testing in spite of the higher costs and loss of data. The active design method could save use of expensive materials.