Tuesday, October 9, 2012

Superpave Pilot Project Changes II

In my last post here I addressed upcoming changes to the paperwork and changes that paving crews should look out for as we progress into Superpave with the pilot projects in 2012 and 2013.  This post will address the changes that the operations groups at hot mix asphalt plants will have to be prepared for.


Asphalt Plants

  • Caltrans will be watching and enforcing the plant's asphalt binder set points now.  Your plant's setting MUST match the optimum binder content that is shown on your JMF when you verify your mix.  If you fail the first verification you will be allowed to adjust the binder set point ± 0.2% from the optimum binder content.  During production, you can only change the set point with written consent by the RE.  This means that you will no longer be able to adjust your plant up or down with changes in your test results but will need to ensure that all of your plant components are operating correctly at all times.  Joe did mention that if you know for a fact that your plant is always set high, for example 0.3% higher than you are actually putting in, you can have this difference approved by your RE prior to starting the job. 
  • There are now tighter HMA production specifications.  For example: air voids are now ±1.5% as opposed to ±2.0% &  Binder Content is ±0.3% in HMA. and ±0.4% for RHMA as opposed as ±0.5% in previous specifications.  The change in binder content specifications is one particular area that industry is extremely worried about.  Caltrans has already heard a plethora of complaints about this change in specification and Joe made sure to mention that these specifications are currently ONLY for the pilot projects and have not been set in stone for the full implementation in 2014.  He fully anticipates changes to these specifications to occur but pointed out that he cannot make a change unless he has the data to back it up.  He encouraged all industry companies to keep careful track of their data over the next couple of years and compile a logical analysis that can prove their contention that the specification will not work.  He is completely open to making a change to the specifications if he has the data to back it up.
  • You will now be told to stop production if you have two out of specification test results in a day.  Unlike before when it would have to be two of the same test results in a row, if you have two of ANY test results out of specification in one day you will need to shut down.  AKA if your sublot 3 is out of specification in binder and sublot 6 is out of specification in SE, you will need to shut down until you can prove that you've made a change that will fix the problems. 
  • The minimum binder content in RHMA is increasing.  The new minimum will be 7.5% TWA and it will probably be moving to 8.0% soon after.  Currently the minimum binder content is 7.0% TWA. 
  • Superpave will produce even bonier mixes!  Most cities will want to move from ¾” to ½” in their design phase.  Due to the bonier nature of the new mixes you will likely be using less SAND and in some cases less dust.  You may need to adjust your aggregate and/or hot plants to account for this.

These specification changes will be the most influential on your future operations and deserve to be examined starting now.  Some plants will need to dial in their binder issues, some will need to alter their aggregate supply's shape, and others will need to hire more staff to be able to test quickly enough to catch problems as they arise.  I know I mentioned it already but I think it's worth a second shout out:

If you feel that your plant will NOT be able to meet some of these specifications start recording data to prove it NOW.  Caltrans is open to adjusting these specifications but industry will have to prove its case.  Step up and do so instead of complaining about the changes.  There are several industry associations such as CalAPA and CalCIMA that are working on these initiatives and the more information and data they have the more likely that they will be successful.

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 RAP.  Stay tuned!

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