Specification Corner
INDIANA DOT
Indiana is switching all binders to MSCR (AASHTO M332) specifications for construction in 2025. At the same time, we changed our base grade from 64-22 to 58S-28. Although the latest version of LTTPBind supports this, the change in base grade also dealt with the fact that all mixes now contain RAP. RAP and the final in-situ grade was never considered in the original decision to be a 64-22 state.
MONTANA DOT
The plan in Montana is to complete our move to MSCR grading for all our binders. We took "baby steps" by switching out our workhorse binder of PG 64-28 for MSCR PG 58V-34 for the past two seasons and we've had good success. We also included a recovery of 55% minimum and with this requirement, we now feel that we can drop down to a 58H-34 for our 'workhorse' binder and leave 58V-34 for our interstates and other higher traffic/load facilities. This has the added benefit of standardizing the MSCR binder grade for our region as North Dakota, South Dakota, Wyoming, and Minnesota are all using 58H-34 now.
NEW JERSEY DOT
NJDOT is increasing the responsible use of RAP by implementing IDT and IDEAL-CT testing. These tests are quicker, simpler, and can be used for QC at the plant. Right now, we are using these tests on pilot projects throughout the state. If things go well, we may increase the number of projects using High RAP specifications with IDT and IDEAL-CT testing.
NORTH DAKOTA DOT
NDDOT has a planned change to include implementing Balanced Mix Design parameters. No significant current changes. NDDOT constructed a field validation test section project in September 2024 with eight test sections totaling 16 lane miles in partnership with NCAT.
OKLAHOMA DOT
Will modify OHDL 26 to remove the ignition chamber dimensions restrictions and possibly change to AASHTO T308. We have been working on our BMD implementation process with eight pilot projects this year, where we are field-testing IDEAL-CT for QC with a shadow spec; we will also run a round-robin in the state with up to 30 registered laboratories that have IDEAL-CT testing capacity.
UTAH DOT
We have changed our asphalt pavement program from SMA and HMA to mostly a UDOT high density HiMod mix. This new mix has proven to be economical and is being fully used, no longer considered in implementation, and is more durable and stronger than any asphalt mix we have used before.
To get the value out of highly modified binders you need to use more of it and close down the voids with it.
Vermont Agency of Transportation
We are transitioning from the 2018 Specifications to the 2024 Specifications. Key changes include adding MSCR to binder grading, requiring 58E-28 for mainline paving, expanding QA to cover all mix quantities, implementing QA for bonded wearing courses, increasing allowable RAP in 19mm NMAS mixes to 25%, and introducing HWT requirements for mix design approval. IDEAL-CT is also under development.
Asphalt Forum
OHIO DOT
Has anyone seen an uptick in pavement debonding/slippage with the use of non-tracking tack emulsions versus a standard M 140 or M 208 (e.g., SS-1h)?
If so, what have you done to work on resolving this issue and do you have any thoughts on the cause of the issue?
MONTANA DOT
Are there any agencies out there who started down the IDEAL-CT path in the name of BMD, but decided to switch to another cracking test such as the DCT for cold weather cracking? Like many, we are not seeing strong trends with the IDEAL-CT, but our benchmarking is just getting started.
NEW JERSEY DOT
We would like feedback from other states about the increased use of RAP and whether they are incorporating balanced mix design with the increased use of RAP.