Mill AC On AC Overly

8 days ago by
I had a DOT Agent send me a comment to my Design or the Approach to using the program. I am doing a typical resurfacing, I.e Mill 2" & Place 2". His comment was "We recommend using existing HMA layers Thickness as is, without deducting milling depth manually and input milling depth in AC Layer Properties’ section" When specifying a milling thickness, will the program not remove the existing and place the thickness of the Overlay specified as a separate layer in the program? Hence maintaining the same grade elevation. Is there another way to do this in the program?
Thanks for your prompt response. So if I have to enter the adjusted existing layer thickness of 5-1.5= 3.5 inches and the new overlay of 1.5 inches then what would be the purpose of the AC Layer Property specifying 1.5 inches of milling? I thought the reasoning behind that aspect of the AC Layer Property was to allow the program to AUTOMATICALLY remove the required existing layer thickness from the existing since I chose the option of AC on AC Overlay.?
written 8 days ago by Christopher Bacchus  
I would recommend that you submit a request to to create a link that automatically removes the thickness if the surface is to be milled.
written 5 days ago by Jay Goldbaum - CDOT  

1 Answer

8 days ago by
The program does not automatically deduct the milled thickness.

We get this question quite often and here is what we recommend.

If milling the existing HMA layer is planned, the designer needs to subtract the milled thickness from the existing pavement structure. For example, if the existing HMA layer is 5 inches and 1.5 inches of milling is planned, then the thickness entered should be 3.5 inches. The milled thickness should also be placed in the "AC Layer Properties" tab under the "Rehabilitation" tab.
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