Monday, October 22, 2012

Superpave Pilot Project Changes IV

As the fourth post in our Superpave series, we'll be focusing on Mix Designs & Mix Verifications.  Our previous posts were as follows: The first post, Changes I, focused on changes to the paperwork and paving procedures.  The second post, Changes II, focused on changes that affect the operations group at hot mix asphalt plants.  The third post, Changes III, focused on the changes that will affect you if you produce RAP and add it to hot mix asphalt.

  • Caltrans is now concerned with the differences between asphalt binder suppliers and is regulating it in the Superpave specifications.  Changing binder suppliers, even if it is the same grade, will require you to submit a new jmf.  In addition, you can only change asphalt binder suppliers once per approved JMF without incurring a charge.  Additional binder supplier changes are $2000 per change.  
  • You can now only verify up to 2 JMFs per job per aggregate size and asphalt binder type.  After 2 it is $3000 each.  This includes reverifications! In addition, Caltrans does not have to turn it around to you in any specific time period.   You will go to the bottom of the priority list and they will work on your JMF when they have time.
Mix Designs
  • I hope you already know this since it is the biggest difference between Caltrans' previous mix design methods and Superpave but Superpave will no longer use the Kneading Compactor in the mix design process.  Instead, Superpave uses a gyratory compactor.  Caltrans has purchased their gyratory compactors from Pine Instrument (  If you plan on purchasing a Pine gyratory compactor there is a several month waiting period so make sure that you are aware of when you need to order to be ready for the Superpave launch. 
  • Caltrans is trying to move away from designing open graded mix designs and estimates that in approximately a year this responsibility may be turned over to the contractor just as the other mix designs are.
  • Superpave will still test for TSR for moisture susceptibility but will also use the Hamburg test to determine its susceptibility to rutting.  You will now have to meet both specifications (minimum dry strength of 120psi and minimum TSR of 70%).  Again, there is a several month waiting period on the Hamburg Wheel Tracking Device and at least one brand has a 15 month waiting list.  Take a look at your budgets now and get one ordered before its too late!
  • The crushed faces test is changing.  Currently a particle is considered crushed if 25% of the face is fractured.  The new procedure will require 50% of the face to be fractured which means that your particles must be 2x more fractured than they were before.  This may cause an an issue at natural deposits and you may have to adjust crushing operations to make sure that you're material is being fractured enough.

We've started a forum for discussing the upcoming changes here: Superpave Discussion Forum.  Please feel free to post any of your questions, opinions, and concerns.  Utilize this area to discuss your findings and work with other companies to make the changes you feel are needed. 

Our next Superpave post will focus on the changes that are coming to your laboratories.  Stay tuned!

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