ASTM D2493 Standard Viscosity-Temperature Chart for Asphalts
5. Procedure
5.1 If the viscosities are not known they should be determined in accordance with Test Methods D2170, D2171, D3205, D4402, or D4957. Viscosities determined at temperatures other than the temperatures specified in each of these test methods may be used.

5.2 For temperatures above 60°C [140°F], plot two viscosity-temperature points and carefully draw a straight line through the points. Plot at least three viscosity-temperature points if the included temperature range is below 60°C [140°F]. Carefully draw a straight line or curve through the points. A point on this line, within the temperature range of the points plotted, shows the viscosity at the corresponding desired temperature.

NOTE 1 - These charts are appropriate for use at higher temperatures, where asphalts are primarily viscous. At lower temperatures most asphalts become viscoelastic. When this occurs, viscosity alone is insufficient to describe an asphalt's flow properties. Most asphalts are primarily viscous at temperatures above 60°C [140°F]. Caution should be used when applying this standard below that temperature.

NOTE 2 - Some asphalts have viscosity-temperature relationships too complex to be represented by only three points, as shown in Fig. 1. In this case determine the viscosity at sufficient temperatures to produce a curve adequate for the purpose intended.

NOTE 3 - Viscosities determined by extrapolation of data may be unreliable

5.3 The viscosity values represented by the data points may have been obtained at different shear rates. This chart does not reflect the shear rate at which the viscosities were determined.

6. Keywords
6.1 asphalt; rheology; viscosity; viscosity-temperature chart