Asphalt Forum

NCAT invites your comments and questions, which may be submitted to Christine Hall. Questions and responses are published with editing for consistency and space limitations.

Randy West, NCAT
What method does your DOT require for determining RAP aggregate specific gravity?

Asphalt Forum Responses

The following responses have been received to questions shared in the previous issue.

Are any other agencies having difficulties with trackless tack materials? -Greg Sholar, Florida DOT

Michael Stanford, Colorado DOT
Not at this time, although we rarely see it used.

Bryan Engstrom, Massachusetts DOT
We are using RS-1h as our standard tack coat hoping that it will track less than RS-1.

Charlie Pan, Nevada DOT
Not in Nevada.

Eric Biehl, Ohio DOT
From a performance standpoint of being non-tracking, we have not had this issue except on high temperature days with or without humidity. We would see some tracking, but not as much as we would with our normal (SS-1h) tack. From an asphalt emulsion standpoint, we have seen the material not be stable and wanting to break in the emulsion bottle or the tank (we have not figured that out yet) prior to testing for acceptance or approval. This typically results in low percent residue and/or low viscosity with or without a failing sieve test. We believe it’s the nature of the material as designed to not only be non-tracking but also break fast. We do not currently perform a bond test on tack coats.

Howard Anderson, Utah DOT
I have not seen it used much in Utah.

Joe DeVol, Washington State DOT
We do not currently use or specify trackless tack materials.