Viscosity Grading For Asphalt Cements: Fid-Bau Portal

Viscosity Grading For Asphalt Cements

J. Skog / G. Sherman

The development of tests for measuring consistency of paving grade asphalts in the range of 40*F to 325*F has led to the development of specifications for specifying grade requirements at 140*F. The purpose of these requirements is to provide uniformity in asphalt viscosity during placement and rolling operations and in service resistance to rutting. It is well known that paving grade asphalts change in viscosity during mixing operations, and that asphalts from different sources change at different rates under the same conditions. Results are presented which show that a series of asphalts having original viscosities at 140*F within a narrow band had a very wide range in viscosity after a test which simulates hot mix hardening. Studies on the relation between asphalt consistency and field 'setting' properties of the paving mixture are presented. These studies involved the use of six paving grade asphalts on one contract. The field 'setting' properties showed a good correlation with the recovered asphalt viscosity at 140*F. The best correlation coefficient with the recovered asphalt viscosity is the viscosity at 140*F after tests simulating mixing, namely the Standard Thin Film or the Rolling Thin Film Tests.