New to Old Concrete Bond

[dcarr82775]

I can't find it, but I would swear in one of the many shear friction discussions someone mentioned that one of the Codes (not ACI) had a bond stress value or a way to calculate it. Am I remembering wrong, or does this exist? IF so what Code was it?

Thanks

 

[structSU10]

In ACI the section on composite flexural members has a calc for the horizontal shear strength, which can give some idea on the bond stress assumed.

 

[KootK]

There was some discussion of this in a recent AJK thread I think. 5 MPa pull-off tests etc.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

Are looking at delamination repair or a second pour kind of thing?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[dcarr82775]

No actual project or instance in mind. I got to thinking (because apparently I think about this stuff when not at work) about joints between existing and new concrete and the bond we all know exists. I thought somebody mentioned there was a code that accounted for it in their version of shear friction. Curiosity on what that value is or how it is quantified is my reason for asking. Might be my memory is wrong and it doesn't exist in a codified manner anywhere

 

[KootK]

Oh my. Have you taken the blue pill and fallen down the infinite rabbit hole that is shear friction obsession? Showers taking too long? Dropping dumbbells on your feet at the gym? Carving weird pumpkins?

In the Canadian code, we separate the two shear friction mechanisms (cohesion & particle interlock). As a result, you can use cohesion on its own if you've good the stomach for it. For roughened concrete, you get 0.25 MPa; for non-roughened, you get 0.5 MPa.

The attached paper may be of interest to you.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[dcarr82775]

Nope not shear friction for once. I saw a fracture in some shotcrete, where the shotcrete fractured and moved with a PT slab. The bond of the shotcrete to the slab (no surface prep at all) was sufficient to fracture the shotcrete. Got me pondering things. So I guess I did have a project in mind, but it isn't a design condition I was looking into

 

[KootK]

That would be a cohesion bond combined with some shear friction clamping force due to gravity loads then, right?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.