1. Warm Mix Asphalt & Recycled Asphalt Pavements
Cassandra Simpson | Greg Stephenson Robert Patience | Rick Hennig

2. WMA + RAP - Benefits Production (temperature)
Product (aggregate and binder)
Environmental (recycle, landfill, etc)
The main production benefit is the ability to run higher temperatures so that the exhaust gasses are at temperatures above their dew point (bag house).
Product benefits of WMA+RAP (which lead to improved performance) include:
Addressing the potential issue of the less aged WMA binder,
Increases the TSR of the resultant WMA+RAP blend
Ensures virgin aggregates are dry (due to super heating) prior to mixing with the virgin binder (and RAP)
Environmental benefits include:
Recycling reduces the dependence on natural resources (aggregates and crude oil)
Reduce “waste” to landfill

3. WMA + RAP - Concerns
Will RAP and New Binders Mix at WMA Process Temperatures?
Co-mixing (or interfacial mixing) of binders (virgin with RAP binder) is being investigated using an atomic force microscope. Additional work is also being undertaken to assess the resultant dynamic modulus of the WMA/RAP blend

4. WMA + RAP - US Practices
Texas DoT – 33%-50% of all WMA work contain RAP
North Carolina (Boggs) – only use WMA with RAP (15-20%)
South Carolina (Banks) – view RAP inclusion as insurance
California (Granite) – a means of achieving a similar binder to that of hotmix
Texas limits the amount of RAP in their specifications to 20% in wearing courses, 30% in the binder/intermediate courses and 40% in lower layers (greater than 100mm from the pavement surface). Also, if the RAP is not processed and fractionated, these maximum allowable limits are reduced by 10% i.e. 10%, 20% and 30% respectively.
North Carolina allows WMA only on secondary roads.
South Carolina limits the amount of RAP in their specifications to 10-20% in wearing courses, 10-25% in the binder/intermediate courses and 30% in base layers and is dependent on the mix type. Banks indicated that RAP eliminates stripping concerns and stiffens the binder to address tenderness/rutting concerns. RAP is also used to bump a PG grade rather than using an expensive intermediate grade (PG76 = PG70+RAP)

5. Specified Binder 58-28 25% RAP Original binder is PG58-28
Original binder (RTFOT Aged) is equivalent to the binder of hotmix after manufacture and placement
WMA (Post Plant) is the binder recovered from a WMA with 25% RAP
HMA (Post Plant) is the binder recovered from hotmix with 25% RAP
This basically indicates that the WMA (Post Plant) binder (containing 25% RAP) and the original binder (RTFOT Aged) are equivalent i.e. the addition of RAP stiffens the (WMA) binder to a level equivalent of the virgin binder in hotmix – addressing concerns that may exist with the tenderness of WMA.

6. Superpave Guidelines
Guidelines for hotmix and potential guidelines for WMA + RAP
Tier 1: Up to 15% RAP (25% for WMA)
use specified binder grade
Tier 2: 15%-25% RAP (25% - 35% for WMA)
use one full binder grade lower
Tier 3: Over 25% RAP (>35% for WMA)
use blending charts to determine required binder grade
Superpave guidelines exist for RAP% in hotmix but not currently for WMA. The values in red are currently being proposed by various industry personnel.

7. Processed coarse RAP (nominal +#4 - 1/2” i.e. 12.7mm – 6.35mm)

8. Processed coarse RAP (nominal +#4 - 1/2” i.e. 12.7mm – 6.35mm)

9. Fine RAP - #4 sieve i.e. – 6.35mm

10. Fine RAP stockpile

11. Fine RAP - #4 sieve i.e. – 6.35mm. Note some agglomerations exist.

12. Questions?