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Publication Number:  FHWA-HRT-15-056    Date:  July 2017
Publication Number: FHWA-HRT-15-056
Date: July 2017


Analytical Method to Measure Water in Asphalt and Its Application to Emulsion Residue Recovery

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FHWA Publication No.: FHWA-HRT-15-056
FHWA Contact: Jack Youtcheff, HRDI-10, (202) 493-3090,



Excess water in asphalt binders and pavement mixes can have a deleterious effect on pavement performance.(1) The addition of water to binders through the use of warm and cold mix technologies highlights the need for accurately measuring water in asphalt. Further, increased water content of biologically derived binders and oils may be responsible for compatibility issues with petroleum-based products. Several analytical techniques have been developed for quantifying water in bituminous material, including the use of Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC), nuclear magnetic resonance (NMR), and others that vary in accuracy, cost, sensitivity, specificity, and ease of operation.

Application of these methods to asphalt has proven difficult for a variety of reasons. Subsequent to evaluation of GC, FTIR, and NMR techniques, the Karl Fischer (KF) method, which is the “gold standard” for measuring the water content in lubricating oils, was considered. KF titration was not considered appropriate for measuring the water in asphalt because of interference reactions with mercaptans, sulfides, and ketones. With innovations in KF reaction solutions such as Hydranal® and Aquastar®, there was new hope that KF titration could be applied to bituminous material. In preliminary studies, samples of asphalt were sent to a commercial laboratory for KF analysis. Inconsistent results suggested that atmospheric water may have contaminated the samples. New laboratory techniques—including storing samples, solvents, and glassware in a dry atmosphere and performing all sample preparation in a dry environment—were employed, and these techniques subsequently improved repeatability to ±20parts per million (ppm)/sample.

FHWA-HRT-15-056 PDF Cover Image



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