Which PG is commonly used as a base grade for asphalt?

• A. PG 76-22
• B. PG 58-34
• C. PG 64-22
• D. PG 82-22

Answer: (C)

Selecting a base PG grade for asphalt binder is about balancing performance in heat with performance in cold. The base grade needs enough stiffness to resist rutting when pavement gets hot, but enough flexibility to avoid cracking in cold weather and to remain workable during mixing and placement.

PG 64-22 is commonly used as the base grade because it sits in the middle of the performance spectrum. It provides solid high-temperature stiffness to handle typical summer temperatures and heavy traffic, while its low-temperature limit of -22°C offers reasonable resistance to cracking in many climates. It also tends to be versatile and workable for standard paving operations, making it a reliable default in many projects.

Other options reflect special needs: very high high-temperature grades like 76-22 or 82-22 are chosen for extremely hot climates or very heavy loads but can be overly stiff for general base use and may complicate mixing and compaction. A softer high-temperature grade like 58-34 trades some high-temp stiffness for potentially better cold-weather flexibility, but that reduced stiffness can increase rutting risk in hot climates.