ASTM D2171 Test Method for Viscosity of Asphalts by Vacuum Capillary Viscometer
8. Procedure
8.1 The specific details of operation vary somewhat for the various types of viscometers. See the detailed descriptions of viscometers in Appendix X1-Appendix X3 for instructions for using the type of viscometer selected. In all cases, however, follow the general procedure described in 8.1.1-8.1.9.
8.1.1 Maintain the bath at the test temperature within more or less 0.03°C (0.05°F). Apply the necessary corrections, if any, to all thermometer readings.
8.1.2 Select a clean, dry viscometer that will give a flow time greater than 60 s, and preheat to 135 more or less 5.5°C (275 more or less 10°F).
8.1.3 Charge the viscometer by pouring the prepared sample to within more or less 2 mm of fill line E (Fig. 2, Fig. 3, and Fig. 4).
8.1.4 Place the charged viscometer in an oven or bath maintained at 135 more or less 5.5°C (275 more or less 10°F) for a period of 10 more or less 2 min, to allow large air bubbles to escape.
8.1.5 Remove the viscometer from the oven or bath and, within 5 min, insert the viscometer in a holder, and position the viscometer vertically in the bath so that the upper most timing mark is at least 20 mm below the surface of the bath liquid.
8.1.6 Establish a 40.0 more or less 0.07 kPa (300 more or less 0.5 mm Hg) vacuum below atmospheric pressure in the vacuum system and connect the vacuum system to the viscometer with the toggle valve or stopcock closed in the line leading to the viscometer.
8.1.7 After the viscometer has been in the bath for 30 more or less 5 min, start the flow of asphalt in the viscometer by opening the toggle valve or stopcock in the line leading to the vacuum system.
8.1.8 Measure to within 0.1 s the time required for the leading edge of the meniscus to pass between successive pairs of timing marks. Report the first flow time which exceeds 60 s between a pair of timing marks, noting the identification of the pair of timing marks.
8.1.9 Upon completion of the test, clean the viscometer thoroughly by several rinsings with an appropriate solvent completely miscible with the sample, followed by a completely volatile solvent. Dry the tube by passing a slow stream of filtered dry air through the capillary for 2 min, or until the last trace of solvent is removed. Alternatively, the viscometer may be cleaned in a glass-cleaning oven, at a temperature not to exceed 500°C (932°F), followed by rinses with distilled or deionized water, residue-free acetone, and filtered dry air. Periodically clean the instrument with a strong acid cleaning solution to remove organic deposits, rinse thoroughly with distilled water and residue-free acetone, and dry with filtered dry air.
8.1.9.1 Chromic acid cleaning solution may be prepared by adding, with the usual precautions, 800 mL of concentrated sulphuric acid to a solution of 92 g of sodium dichromate in 458 mL of water. The use of similar commercially available sulphuric acid cleaning solutions is acceptable. Nonchromium-containing, strongly oxidizing acid cleaning solutions may be substituted so as to avoid the disposal problems of chromium-containing solutions.
8.1.9.2 Use of alkaline glass cleaning solutions may result in a change of viscometer calibration, and is not recommended.
9. Calculation
9.1 Select the calibration factor that corresponds to the pair of timing marks used for the determination, as prescribed in 8.1.8. Calculate and report the viscosity to three significant figures using the following equation:
Viscosity, Pa•s = (Kt)
where:
K = selected calibration factor, Pa•s/s, and
t = flow time, s.
NOTE 5 - If the viscometer constant or calibration factor (Kcgs) is known in cgs units (Poise/s) calculate the calibration factor (Ksi) in SI units (pascal•seconds/second) as follows:
Ksi = (Pa•s/s) = Kcgs/10 or (P/s)/10
