Specification Corner

Florida DOT

We will allow 9.5 mm NMAS mixtures to be used in FDOT's highest traffic loading roadways, provided the layer is a minimum of 1.5" thick. This is based on sponsored research.

Indiana DOT

Indiana is planning to make significant changes to binder specs by 2025. We are currently a PG 64-22 base grade state, and specify AASHTO M 320. We are concurrently moving towards being a PG 58-28 base grade state, and implementing AASHTO M 332 specs for projects starting in 2025. This change was due to a number of factors, including a recently completed research project, recommendations of an outside expert hired by APAI, and observations on performance on pilot projects using -28 grade binder.

Minnesota DOT

We are requesting for each of our districts to build 2 Superpave5 projects, or approximately 10 total projects for 2023. 

Mississippi DOT

Last year we switched from external angle calibration requirements of the gyratory compactor to internal angle. We saw that only two or three mix designs needed to be redesigned because of the change in angle. We allow contractors to pick which brand gyratory they would like to use. Some choose to use Troxler. The older Model 4140 is getting phased out for the Model 5850 which cannot be externally calibrated. This is the major reason we decided to change our specification.

Montana DOT

We are implementing one grade of MSCR binder this season. Montana is a 58-34 PG state from LTPPBind data but we've been paving with -28 grades for some time so we're bumping down to -34 along with implementing MSCR. We found that 58V matches our current PG 64 binders so we're going with 58V-34 as a replacement for 64-28. That may be overkill, with a 58H being more appropriate for our traffic level, but that's what we need to investigate. We're also going to test our mixtures in the Hamburg at two temperatures, 44 C and 50 C, as part of our efforts to tier our Hamburg criteria in relation to traffic level. We varied test temperature based on PG temp before, but now that our PG temp will stay constant, we must determine the appropriate test temp so we can focus on varying number of passes in the Hamburg for different traffic levels.

North Carolina DOT

We are in the final stages of revising and updating our Standards and Specifications Book for 2024. We are also conducting research in friction and macrotexture to evaluate any current issues related to friction and texture.

Virginia DOT

Planned changes to our specifications for 2024 include 92.5% min. density for ALL asphalt layers, allowing lift thicknesses up to 5x NMAS. In the balanced mix design area: All SM-9.5 and 12.5 A and D mixes on maintenance schedules will be designed using our BMD criteria. D mixes will be performance tested during production to meet required thresholds.