Both ASTM and AASHTO recognize the importance of proper sample handling to achieve valid test results. They recognize that all asphalt emulsions are made hot typically 180° to 200° F (82° to 93° C), some grades are stored hot typically 150° to 180° F (66° to 82° C), and that some of these hot stored grades are subsequently transported and applied at temperatures above 140° F (60° C). Hot samples collected in the field usually arrive at the laboratory at ambient temperature. How should these samples be handled? The language in ASTM D244 and AASHTO T-59 is significant and similar, with AASHTO stating:
All emulsions with viscosity requirements of 50° C (122° F) should be heated to 122 5° F (50° 3° C) in a 160° F (68° C) water bath or oven. The container should be vented to relieve pressure. After the sample reaches 122 5° F (50°3° C), stir the sample to achieve homogeneity.
The above statement recognizes that the viscous grades of emulsion, those tested for viscosity at 122° F (50° C), generally give low, false viscosity values if manipulated or handled in the laboratory at ambient temperatures. The key to this sample-conditioning step is that if the sample is NOT stirred or agitated prior to heating to 122° F (50° C), it will give a more realistic laboratory viscosity like that experienced at the jobsite. This recovery of the jobsite viscosity is quite independent of the duration of ambient temperature storage of the sample.