Quantification of Water in Asphalt by Karl Fischer Titration and Its Application to Emulsion Recovery

Abstract

In this study, the Karl Fischer (KF) titration method for quantification of water was successfully applied to asphalt binder. Previously, observed side reactions between the titration solvent and certain functional groups present in asphalt prevented accurate KF-type titration. However, recent advances in KF solvent formulation have allowed for rapid titration of water in asphalt with minimal interference reactions. Repeatable results were obtained with moisture-sensitive techniques such as drying glassware, using only anhydrous solvents, and performing all sample preparation in a dry atmosphere. The developed KF titration method was implemented in the evaluation of three competing laboratory asphalt emulsion residue recovery procedures. All three methods showed sufficient removal of water for rheologic testing of the eight recovered residues. Measuring the water content in recovered residues by the mass lost at 135°C was not suitable for some emulsion residues because of the evaporation of nonwater solvent or distillate at the elevated temperature.