ASTM D6373-16

1.1 This specification2 covers asphalt binders graded by performance. Grading designations are related to the average seven-day maximum pavement design temperature, and minimum pavement design temperature. This specification contains Table 1 and Table 2. Table 2 incorporates Practice D6816 for determining the critical low cracking temperature using a combination of Test Method D6648 and Test Method D6723 test procedures. If no table is specified, the default is Table 1.

(A) Pavement temperatures are estimated from air temperatures using an algorithm contained in the LTPP Bind software program, or are provided by the specifying agency.

(B) The referee method shall be D4402 using a #21 spindle at 20RPM, however alternate methods may be used for routine testing and quality assurance. If the binder is too stiff to test with the No. 21 Spindle, the No. 27 spindle shall be used. The spindle size and shear rate shall be reported. This requirement may be waived at the discretion of the specifying agency if the supplier warrants that the asphalt binder can be adequately pumped and mixed at temperatures that meet all applicable safety standards.

(C) For quality control of unmodified asphalt cement production, measurement of the viscosity of the original asphalt cement may be substituted for dynamic shear measurements of G*/sinδ at test temperatures where the asphalt is a Newtonian fluid. Any suitable standard means of viscosity measurement may be used, including capillary viscometry (Test Methods D2170 or D2171) or rotational viscometry.

(D) The PAV aging temperature is based on simulated climatic conditions and is one of three temperatures 90°C, 100°C or 110°C. Normally the PAV aging temperature is 100°C for PG 58–xx and above. However, in desert climates, the PAV aging temperature for PG 70–xx and above may be specified as 110°C

(E) If the creep stiffness is below 300 MPa, the direct tension test is not required. If the creep stiffness is between 300 and 600 MPa the direct tension failure strain requirement can be used in lieu of the creep stiffness requirement. The m-value requirement must be satisfied in both cases. If the creep stiffness and m-value data are unobtainable because the binder is too soft at the test temperature, the asphalt binder will be deemed to pass at that grade temperature if it meets the creep stiffness and m-value requirements at the test temperature minus 6°C.

(A) Pavement temperatures are estimated from air temperatures using an algorithm contained in the LTPP Bind software program, or are provided by the specifying agency.

(E) For verification of grade, at a minimum perform D6648 at the test temperature and at the test temperature minus 6°C, and D6723 at the test temperature. Testing at additional temperatures for D6648 may be necessary if 300 MPa is not bracketed at the initial two test temperatures. Compare the failure stress from D6723 to the calculated induced thermal stress as per D6816. If the failure stress exceeds the induced thermal stress, the asphalt binder is deemed a “PASS” at the specification temperature. If the creep stiffness and m-value data are unobtainable because the binder is too soft at the test temperature, the asphalt binder will be deemed to pass at that grade temperature if it meets the critical low cracking temperature requirements at the test temperature minus 6°C.

Note 1: For asphalt cements graded by penetration at 25°C, see Specification D946. For asphalt cements graded by viscosity at 60°C see Specification D3381.

Note 2: AASHTO R 29 provides non-mandatory information for determining the performance grade of an asphalt binder.