Superpave Wearing Course

[cnstengineer]

I’m working on a project that has a paving spec of 4” BCBC and 2” of wearing. The wearing course is specified as 12.5mm superpave. It has been requested to substitute the 12.5mm superpave with a 9.5mm superpave mix. What are the advantages/disadvantages to using a mix with a finer aggregate? I know that it is preferable to have a minimum paving thickness of 2-3 times the largest aggregate size, but is there any concern with a maximum paving thickness? This project is a new parking area in Pennsylvania that will be subject to freeze/thaw.

 

[HuntPA]

2" is about the thickest that I have seen 9.5 used successfully. It does seal a little better than the 12.5, but with that thickness, there may be more issues with rutting. I personally would stick with the 12.5 if it is going to be a 2" lift. If they want to do a 12.5 scratch with 9.5 surface, that would be fine, but they probably wouldn't want the extra labor associated with another pass.