What the Low-Temperature Number on a PG Grade Means

The number after the minus on a PG grade is the low temperature, in Celsius, the binder was graded to resist cracking. Minus 22 and minus 28 are different winter grades. The grade is a material spec, not the air temperature on paving day.

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The minus number is a cracking grade

The number after the minus sign on a performance grade is the low temperature, in Celsius, that the binder was graded to resist cracking. On a PG 64-22 binder, that number is minus 22. It describes how the binder behaves in cold pavement, not how cold the air feels at noon on paving day. A binder can meet a winter grade and still be impossible to compact if you try to pave into a deep freeze. Read the minus number as a material spec you can compare between quotes. Write it next to the high number so you do not treat 64-22 and 64-28 as the same product with a typo.

Minus 22 and minus 28 are different winters

A minus 22 and a minus 28 are not the same winter grade. The lower number is the colder grade. Colder regions use a lower number because their pavement reaches colder temperatures. If your plant quotes minus 22 and a neighbor's road spec shows minus 28, ask why before you decide one quote is incomplete. The state specification picks grades for public roads. A driveway plant ships what it produces for local work. Ask them which low temperature number is in the surface mix they will load, and ask them to say it as a temperature grade rather than as a vague winter mix. The scale ticket should show the full grade, high number and low number together.

The grade is not a paving forecast

Nothing in the minus number gives you permission to pave in deep winter, and nothing in it is the morning air temperature. Crews still need mix that is hot enough to compact, a base that is dry and firm, and air that is not pulling heat out of the mat faster than the roller can work. The grade tells you what the binder was designed to survive after it is in service. Thickness and base still carry the loads. For a planning estimate, compacted hot mix is about 145 pounds per cubic foot, and the plant ticket is the real weight. Changing from minus 22 to minus 28 does not change that density unless the plant says the mix itself is different. Keep the winter grade and the tonnage on separate lines.

A practical sequence

Read the number after the minus as a low temperature in Celsius.
Treat minus 22 and minus 28 as different winter grades.
Ask the plant which low number is in the mix they will ship.
Keep paving-day weather separate from the binder grade on the ticket.

The mistake to skip

Reading the minus number as the air temperature required on paving day.

Questions people ask

Does minus 22 mean I can pave at 22 degrees?

The minus 22 is a Celsius low temperature grade for cracking resistance in the binder. It is not the air temperature on paving day, and it does not mean winter paving is appropriate. Ask the plant which grade they ship. Compaction still depends on hot mix, a firm base, and weather the crew can work in.

Is a lower minus number always better?

A lower number is a colder winter grade, and colder regions specify it for a reason. It is not an automatic upgrade for every driveway. Ask the plant what they ship locally and why a quote names a different low number. The high temperature number is a separate part of the grade. The ticket should show both.

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