Specification Corner

Colorado DOT
We have developed Project Special Provisions for cape seal and double chip seal as statewide specifications options for our low volume roads. We have also developed a polyphosphoric acid (PPA) Pilot Project Special Provision to be used at the discretion of the Regional Materials Engineer.

Florida DOT
Effective with projects bid starting January 2017, PG 76-22 (PMA) and PG 76-22 (ARB) are considered equivalents, and it is the contractor’s choice as to which binder to use. Both binders must meet the same testing requirements with the addition of the separation test for the ARB binder. Effective July 2017, PG 82-22 (PMA) will be replaced by PG 76-22 (HP) binder, often referred to as HiMa binder. This will be our premium binder and will be used in locations with the potential for severe rutting or cracking. We will now refer to the binder as “HP” binder.

We are now allowing cellulose fibers to be used in OGFC mixtures with the same binder content as required for mineral fibers. Previously, the OGFC designs with cellulose fibers had higher AC contents than those designs with mineral fibers. Cantabro testing confirmed that the mixtures are equally as durable with the same AC content and different fiber types. Contractors using cellulose fibers are experiencing better laydown without any draindown, cleaner trucks, and better conditions for asphalt plant workers who handle the fibers.

Minnesota DOT
Effective 2017, all projects are using the MSCR specification for binders.

Montana DOT
We have moved to limits on binder replacement rather than limits on RAP as a percent by weight of mix. We are also using the Hamburg wheel tracking test more often for field acceptance when there are volumetric issues. For example, if a sample fails volumetric test criteria, Hamburg testing is performed to determine if the material should be left in place. We have also instituted a longitudinal joint specification.

Ohio DOT
We are looking to fine up the gradations of our 19 mm mixtures to help resolve segregation issues and to add more virgin PG binder. Numerous lab mixes were made by ODOT and contractors to determine minimum virgin and total AC %. We are also planning on revising our micro-surfacing specification to increase contractor QC testing and controls and to update to the current ISSA and AASHTO requirements.

South Carolina DOT
We have revised our SC-M-402 specification to get back to a finer surface mixture for use beneath our OGFC. We now specify a 9.5mm mix with 75 gyrations versus the 12.5mm mix with 100 gyrations used previously. We are also getting more binder to be added to RAP/RAS mixtures by using a 75% availability ratio for the percentage of aged binder (similar to Georgia DOT).

Tennessee DOT
We now allow 10% RAP regardless of processing/fractionation for all of our AS-mix (open-graded base mix) as long as the final gradation meets the master gradation range. This had previously ranged from 0 -15% depending on processing/fractionation and had restricted RAP particle size. We also require all AS-mix to be covered prior to winter or refrain from paving with AS-mix until spring.

The minimum placement temperature for OGFC mixes has been lowered to 280° F.

We now require the use of 75% skid-resistant aggregate in our ‘scratch’ mixes when used as a riding surface.

Our MSCR specification has been modified as follows:

  1. % Difference (Jnr 3.2 - Jnr 0.1) is not applicable for PG 76-22 and will be waived for PG 70-22 if the Jnr (3.2) is less than 0.5.
  2. Minimum % Recovery for PG 70-22 is now a flat 29%. The recovery curve in AASHTO M332 Appendix X1 still applies to PG 76-22 and PG 82-22.