In the Performance Grade (PG) standard 64-22, what does the first number 64 represent?

In the Performance Grade (PG) standard, the first number in the designation, such as 64 in 64-22, specifically indicates the high temperature grade of the asphalt binder. This number corresponds to the maximum temperature at which the asphalt is expected to perform well without experiencing significant deformation or failure.

The PG grading system is designed to help engineers select the right asphalt binder for specific environmental conditions and loading scenarios. A PG 64-22 binder can handle high temperatures up to 64 degrees Celsius while still maintaining its structural integrity. This is crucial for ensuring durability and longevity of the pavement under the operating conditions it will face.

Understanding the high temperature grade is essential for predicting how the asphalt will behave during hot weather and heavy traffic, ensuring safety and performance in roadway applications.