The AASHTO Subcommittee on Materials met in South Lake Tahoe, Nev. from August 4-8. “Technical Session 2B, Asphalt” held a discussion on the status of a few ballot item to allow the use of recycled tire rubber as an asphalt modifier. Some clarifications were added to the ballot items from the spring meeting. A basic summary of the clarifications is that recycled tire rubber will be allowed as a specific particulate modifier, and when it is used, the DSR will be used at a 2 mm gap.
- M320 – PG Asphalts, allow tire rubber modifier as a particulate with a limit at 600 microns in size (30 mesh)
- T44 – Solubility Test, a waiver may be provided if the insoluble material is identified as recycled tire rubber
- T315 – The DSR, a 2 mm gap will be used when particulate RTR is identified as the modifier
- MP19 – PG asphalt using MSCR, the 2mm gap will be used when RTR is the modifier
The revised ballots will go to the voting members in November and the balloting will close in December. If the rubber items pass, then the revisions will take effect in 2014.