In PG 58-22, what do the numbers 58 and -22 represent?

• A. 58 = high-temperature tolerance; -22 = low-temperature tolerance
• B. 58 = low-temperature tolerance; -22 = high-temperature tolerance
• C. 58 = viscosity value; -22 = penetration value
• D. 58 = road age; -22 = binder weight

Answer: (A)

Performance Grade (PG) binders are described by two numbers that show temperature performance in Celsius. The first number, 58, is the high-temperature grade: it indicates the temperature up to which the binder can withstand heat without losing too much stiffness or sagging into rutting. A higher value means better resistance to softening at hot pavement temperatures. The second number, -22, is the low-temperature grade: it marks the lowest temperature at which the binder should remain workable and resist cracking. The negative sign shows this value is below freezing, and a more negative number means better performance in very cold conditions. So PG 58-22 means it’s rated for about 58°C at high temperatures and about -22°C at low temperatures.