small slab opening infill

[structSU10]

I have to infill 18" square openings down to 6" square opening in a concrete slab. I typically have the edges tapered to create a wedge on all sides that is wider at the top. for such a small opening, I cant really dowel the infill into the existing concrete. Along the tapered edges, the force can be resolved as a direct shear and an axial compression. I want to keep the taper fairly shallow, so I don't get enough compression to resist the shear on its own, but the main question is, is the aggregate interlock across this surface going to be enough that I shouldn't worry about it? we are only talking maybe 300# per face max.

 

[KootK]

I see what you mean. That's just small enough to be it kind of awkward to deal with. Some ideas:

1) With the taper, I'd not be at all worried about downward vertical. What little concern I'd have would probably be to do with the thing popping out upwards under some, hard to predict, straining in the structure.

2) This will sound kind of amateur but could you get a handful of partially installed Tapcons into you slab edges to get a nominal connection?

3) If you wanted to get serious about it, you could probably saw cut and grout a pair of 4' bars into the slab across the opening in one direction. If the original opening was a planned part of the original slab, then you might be cutting trim bars by doing this. And I'd prefer not to have that happen.

 

[hokie66]

You should be able to drill down at an angle to insert some small dowels.