What does the second number -22 in the PG standard 64-22 represent?

In the context of the PG standard 64-22, the second number, -22, indicates the low temperature performance grade of the asphalt binder. This designation reflects the ability of the binder to withstand low temperatures without becoming too brittle or failing to perform adequately.

Asphalt binders are classified based on their performance at various temperatures, which helps in selecting the right material for specific climate conditions and applications. The negative value signifies that the binder is designed for use in regions that can experience low-temperature conditions, ensuring that the asphalt remains flexible enough to handle thermal contraction and other stresses without cracking. This is critical for maintaining road integrity and safety in colder climates.

The other options do not accurately reflect what the second number signifies:

• High temperature relates to the first number in the grading system.

• Average temperature is not a standard term used in the context of PG grading.

• Maximum density is unrelated to the performance grades specified by the PG standards.