This brings the sample to temperature quickly, which can vary anywhere from 100oF (38oC) to 500oF (260oC), depending on the specific test.

The jacketed container into which the chamber is placed for testing has built-in temperature control. Both are now available as disposable items, which saves the operator time by avoiding the messy cleanup after the test. As mentioned above, common choice of spindle is Brookfield number 27, in which case the sample size is slightly over 10mL. The 13R chamber is traditionally used and requires 16mL of sample or less, depending on the spindle that is immersed in the binder. It is important to set viscosity limits based on desired flow behavior properties that have been gained from field experience.Ī potential improvement in the equipment to expedite testing is choice of disposable chambers. When the viscosity exceeds the target value, the consequence may be difficulty with pumping and subsequent problems with placement of finished product. Manufacturers have defined target values for viscosity based on experience with different formulations. This test evaluates the pumpability of the asphalt. The rotational speed is either 10 or 20 rpm and the viscosity reading is recorded in units of centipoise. D-4402 defines the methodology for placing the sample in a chamber, which is then heated and measured for viscosity using a rotating spindle-normally Brookfield number 27-immersed in the binder. The American Society of Testing and Materials recommends method D-4402 for testing asphalt binder in the lab: “Standard Test Method for Viscosity Determinations of Unfilled Asphalts Using the Brookfield Thermosel Apparatus.” Figure 1 shows the Brookfield thermosel system. For example, in automatic blending control systems, viscosity measurement can be used as the process feedback variable to regulate temperature, mixing and heating times, and addition of performance enhancing additives. Measurement of binder viscosity in pipes or tanks during manufacturing can assure that the binder satisfies established QC parameters and that the production plant is performing to spec. Inline process viscometers have been in existence since the 1980s, and offer this alternative. While the benchtop viscometer is a popular instrument of choice for testing, there is another way to obtain viscosity data in a timely fashion. Highway departments in each country have practiced this method of testing even before the Strategic Highway Research Program in the United States began the practice more than 25 years ago. Asphalt labs around the world use rotational viscosity to measure binder viscosity.

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