Specification Corner

Alabama DOT
Alabama has a possible cold central plant recycling specification in the works, we are updating our milling specification, and we are updating tack and joint sealant specifications to match the latest research.

One balanced mix design trial project is complete and another has been scheduled.

Colorado DOT
Colorado DOT is looking at developing a pilot project specification for alternative binders on cold in-place recycling projects.

Delaware DOT
Delaware DOT is currently looking into creating a trackless tack specification.

Florida DOT
Florida DOT has one substantial change for the January 2021 asphalt specifications regarding the amount of allowable RAP in a mixture. The change came after the University of Florida completed a funded research project for FDOT. The amount of RAP will now be based on its gradation (% passing the No. 16 sieve and high temperature recovered binder grade). These changes apply to all mixtures that contain a PG 76-22 PMA binder and are placed below the surface layer. Criteria are established for coarse RAP, intermediate RAP and fine RAP. The coarser the RAP and the lower its PG grade, the more of it can be used.

Michigan DOT
We are reducing the number of Superpave mixes to align with AASHTO guidelines and national best practices with implementation corresponding with new standard specifications that will be implemented starting with the August 2021 letting.

Montana DOT
We have implemented a longitudinal joint compaction specification on most paving projects of 91% minimum in most situations and 90% minimum on thin lifts. A 1.05 pay factor is applied to lots with 92% to 95% compaction using $4.50/foot of joint as a unit cost. The special provision can be downloaded at mdt.mt.gov/other/webdata/external/const/specifications/special-provisions/401-02-LONGITUDINAL-JOINT.docx.

We have also added an option to accept mix on a tiered scale in certain situations when it performs poorly in the Hamburg, found in Section 400 of our standards at mdt.mt.gov/business/contracting/standard_specs.shtml.

Oklahoma DOT
Oklahoma DOT is currently moving from PI to IRI, implementing balanced mix design and limiting the use of REOB, PPA and establishing Delta Tc limits.

Utah DOT
We continue to have good success with our Delta Tc binder specification as it has replaced our direct tension specification.

Vermont AOT
We have instituted a requirement to have Hamburg and I-FIT results be submitted for mix designs on mainline paving operations. These results are for informational purposes only, but project-specific pass/fail criteria has been piloted on three agency projects. We have begun looking at the IDEAL suite of rutting/cracking tests as "surrogate" tests during QA production.

We have dropped the minimum 0.5% dosage rate requirement for anti-stripping additives in mix designs containing granite and/or quartzite aggregates. Instead, we will start requiring ASTM D 3625 (boil test) results to be submitted with each mix design, with weekly testing conducted during production of each approved mix design to verify that no change in stripping potential has occurred.

We are planning on switching to AASHTO M 332 MSCR grading for our PG binders in the near future. A firm switchover date has not yet been established due to COVID-19 and other internal challenges.

We have been hard at work developing a new tiered approach to our HMA specifications, which would see almost all mixture acceptance testing fall under QA testing protocols and allow for sampling of mixtures using other methods allowed under AASHTO R 97. We expect to have these revisions finalized for the next edition of our Standard Specifications for Construction to be tentatively published for the 2023 construction season.

West Virginia DOT
West Virginia tentatively plans to eliminate Marshall mix design and introduce balanced mix design.