An alternative to scarifying. 2

[WARose]

I’ve got a job where the detail I am using asks the contractor to scarify the top 1” of a concrete pad (before the application of an epoxy grout). I was wondering: rather than the labor involved with doing that, why not [as an alternative] use some type of embedded form that would achieve the same thing? It seems like (some years back) I saw something like this. It was sort of like a plastic grid deal that had an edge sort of like a saw tooth or something……except that the “teeth” were kind of square.
Has anyone seen something like that or can recommend a good alternative?

 

[Ron]

WARose...scarifying is not necessarily labor intensive. Why do you have to go so deep? Most surface scarification or grit blasting are only carried to 1/4 or 1/2".

BlastTrac works very well for this. It is easy to use, relatively clean and provides a good profile for epoxy toppings.

 

[WARose]

The detail I am following wants scarifying that deep so to insure a good bond between the epoxy grout and the [scared] surface.

I always thought BlastTrac produced a smooth surface.....will look into it more.

 

[JLNJ]

I believe ACI specifically calls for 1/4" amplitude for items such as shear friction. More seems un-necessary.

 

[WARose]

Sitting on this will be a compressor with some significant out of balance forces [i.e. dynamic loads]. I.e. it is desired that we insure there is good bond (thus the high amplitude). Everywhere I’ve worked that did compressor bases this was a fairly common detail.

One thing that concerns me with that amplitude is: you are going to have chips/debris lying around everywhere.......and if the contractor doesn’t clean/sweep it off good, your grout will bond to debris (which is obviously not desired). So that’s what prompted my question (i.e. a non-destructive way to get that).

 

[hokie66]

Scarifying to 1" depth takes a big hammer, with a lot of compressive effort. It does more damage than good, as it causes microcracking in the concrete. All you really need is a clean and slightly roughened surface. As Ron indicated, this can best be achieved by grit blasting.

 

[JedClampett]

I'd save the labor, microcracking and the general mess. Dowel the foundation using epoxy. Use shear friction to carry the shear loads and the dowels to carry any moments. I'd rather have quantifiable materials like dowels than worry how much scarification can fit on the head of a pin.