What does a PG binder with a grade of 70-28 indicate?

A PG binder graded as 70-28 indicates its temperature performance characteristics based on the Performance Grade (PG) system used in hot mix asphalt design. The first number, 70, represents the high-temperature performance rating, which signifies that the binder is expected to perform well in temperatures up to 70 degrees Celsius (approximately 158 degrees Fahrenheit). This suggests that it is suitable for warmer climates where higher temperatures can be reached.

The second number, -28, indicates the low-temperature performance capability, which shows how the binder will perform in colder conditions, with the negative indicating that it is effective down to -28 degrees Celsius (approximately -18 degrees Fahrenheit). However, the primary message here is about its suitability for warm climates due to the high-temperature rating.

This understanding of the PG grading system helps in selecting appropriate binders for specific environmental factors, ensuring that the roadway will withstand the traffic and weather conditions typical of warmer regions without excessive deformation or failure.