• This is a journal article. It was published in the journal, Transportation Fleming, Frost, and Lambert 2 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. This paper reviews the LWD as a field evaluation tool, discusses the test variables and data quality and concludes both on its usefulness and also its limitations for a variety of earthwork and road assessment scenarios. The paper aims to provide a state of the art reference document for LWD users, consultants, material specifiers, contractors and clients. It reviews data from road foundations (subgrades, granular capping and sub-base) and fully constructed in-service (thinly surfaced) roads, to demonstrate the flexibility of the LWD but also show that its determination of 'stiffness modulus' may differ from that of the conventional Falling Weight Deflectometer (FWD) to a varying extent. A series of laboratory investigations are presented that demonstrate the sensitivity to uniformity of plate/surface contact, and also limitations in the interpretation of peak displacement from the device. In conclusion, a good understanding of the device workings and careful specification of the test variables are required to both analyse the data correctly and permit comparison between data sets. The device is concluded to be a useful and versatile field quality control and pavement investigation tool, if an understanding of the device issues is considered by data users.
INTRODUCTIONThis paper reviews the use of portable falling weight deflectometers (PFWDS) and the behaviour of the Lightweight Deflectometer (LWD) in detail. In this paper the term PFWD means any portable device for measuring a stiffness of material insitu, and the term LWD refers to the specific type of PFWD commonly known in Europe as the Prima, manufactured by Carl Bro (previously manufactured by Keros). The LWD is increasingly used for investigations of road construction materials and quality control. A background to the LWD development, a review of field data with a focus on correlation with the Falling Weight Deflectometer (FWD), and then specific laboratory investigations are presented. This paper is intended for reference by LWD users, consultants, material specifiers, contractors and clients.
Combinations of the broad spectrum, demand-type quaternary ammonium resin-polyiodide bactericide and virucide were prepared in the triiodide, pentaiodide, and heptaiodide forms by fluidized bed method in a closed aqueous system at elevated temperatures. The resin-triiodide combination is now in use as a disinfectant for water. The triiodide disinfectant prepared by this method is equal to the product obtained by a room temperature batch contact process and can be prepared in a considerably shorter time. Analyses of the supernatant solutions revealed increasingly higher iodine concentrations with higher polyiodide species in the resin combination. A long run elution study of one resin-pentaiodide combination is reported. All combinations, from triiodide to heptaiodide, were in the form of black, shiny beads, with increasing contraction of the beads observed with increasing iodine content. A significant fraction of the resin-heptaiodide beads were fractured due to internal stresses which caused the contraction.
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