Compaction temperature is the temperature at which the binder reaches a kinematic viscosity of 280 ± 30 cSt.

• A. It is the ambient temperature
• B. The temperature at which the binder reaches 280 ± 30 cSt
• C. It is the temperature at which the mixture begins to oxidize
• D. It is the temperature for the aggregate

Answer: (C)

Compaction temperature is defined by the binder’s flow characteristics. It is the temperature at which the asphalt binder reaches a viscosity of about 280 ± 30 cSt. This specific viscosity is chosen because it strikes the right balance: the binder is soft enough to allow the mix to be compacted easily with rollers, yet not so fluid that the mix becomes prone to drainage or excessive aging. If the temperature is too low, compaction becomes difficult and the pavement may are prone to poor density and segregation. If the temperature is too high, the binder can age more quickly and the mixture can become unstable. Ambient air temperature or oxidation aren’t the criteria used to set compaction temperature, and the aggregate temperature alone doesn’t determine the proper viscosity needed for proper compaction.