When the percentage of available RAS or RAS + RAP binder in the total binder exceeds 15%, AASHTO recommends a PG adjustment (one grade softer) for the base asphalt binder.

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Multiple Choice

When the percentage of available RAS or RAS + RAP binder in the total binder exceeds 15%, AASHTO recommends a PG adjustment (one grade softer) for the base asphalt binder.

Explanation:
When recycled materials contribute a portion of the binder, the aged asphalt in RAP or RAS is stiffer than new binder. To offset that stiffening and maintain proper performance across temperatures, AASHTO guidance calls for adjusting the base binder to be one PG grade softer if the available RAS or RAS+RAP binder in the total binder exceeds 15%. This single-step softening helps keep workability and rutting resistance balanced without overshooting and making the mix too soft. It’s not about mixing with RAP only or using two grades softer; the standard specifies one grade softer to adequately compensate the aging effect.

When recycled materials contribute a portion of the binder, the aged asphalt in RAP or RAS is stiffer than new binder. To offset that stiffening and maintain proper performance across temperatures, AASHTO guidance calls for adjusting the base binder to be one PG grade softer if the available RAS or RAS+RAP binder in the total binder exceeds 15%. This single-step softening helps keep workability and rutting resistance balanced without overshooting and making the mix too soft. It’s not about mixing with RAP only or using two grades softer; the standard specifies one grade softer to adequately compensate the aging effect.

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