Concrete chunk fell off of entrance stairs

curls00

I stopped by Rona (Canadian home improvement store) today and they carried a product by "bomix" (Eastern/Central Canadian company). Here is the one I was recommended: http://www.bomix.ca/produits.php?id=...p&lang=en&p=20

It's a quick-setting, high-bond repair mortar. Sounds like what you linked to, but a different brand. My only concern is that it says maximum 3" thickness. I haven't looked at it thoroughly, but my repair, if I take out that bottom chunk (which I will do), will be about 12" high. But, the thickness from front to back wouldn't be much more than 3" though. Which measurement do I take? The picture for that product shows almost the exact area where my step broke... so I'm thinking it'll be OK.

I'll pick up some anchoring epoxy tomorrow, as well as the threaded rod.

Cheers,
Eric

curls00

Oh, here's the technical specs for the bomix stuff:

Compressive strength ASTM C-109
3 hours -- 6.3 MPa (913 psi)
1 day -- 12.2 MPa (1770 psi)
7 days -- 16.0 MPa (2320 psi)
28 days -- 20.0 MPa (2900 psi)


versus the specs for your Quikrete commercial grade:

Compressive strength, ASTM C109 Modified
3 hrs -- 2000 psi (13.8 MPa)
24 hrs -- 4000 psi (27.6 MPa)
28 days -- 6000 psi (41.4 MPa)


Is the BIG difference (basically 2x stronger) going to matter for this application? Or, with pins, will the stuff I am thinking about work just fine?

Maintenance 6

You're not going to drive a truck up and down the steps, so compressive strength isn't such a big deal. It looks like what you plan to use should work fine

kgphoto

Cement-All will work very well there. High strength, quick set.

Your patch will always show as a patch as the color will not match. The high priced mason was giving you a very good product if you read the specs. He was going to take out the wood and pour a whole step. It would have looked better than a patch. You get what you pay for.

curls00

If it ends up looking horrible, I was planning at some point to paint the steps with the textured concrete paint in a colour other than concrete grey. Maybe that will be done sooner than later. Either way, that corner of the step is not noticeable from the street and 90% of the time, not even noticeable when walking up to the door since it's on an inside corner that people walk away from (partially).

curls00

Ok, we're finished the repair! I forgot to take pics of the threaded rods/pins we epoxied in place, but we did definitely do that (x4 of them, 3" into the existing concrete, 2"+ each for the new concrete). The piece of wood was perpendicular to the front of the step (the face), so we chiseled it out completely (it was sopping wet!), and then put some dense styrofoam panels loosely placed in the void left by the removed wood piece. This was because it would have been hard to get a good pack of the new concrete back in that area, so the styrofoam will fill the area without expanding much, and since it's got a tiny bit of room to play with, it shouldn't put any force on the concrete. We also put a small plastic tube (thick, strong) for drainage from that area, down below grade to the gravel below the paving stones.

Here's the top view of the mold (we used the same dense styrofoam for the kickplate area (?) and then a lightly-oiled 2x board for the end of the nose.


Here's the finished product:






I will probably grout or caulk the very edges of the vertical patch to give it a bit better look, but overall it should be plenty strong, and isn't too noticeable (and once it's a bit dirty it should blend right in, hahaha!).

Oh, and I plan to cut the expansion joints next time I have a few moments.

Thanks everyone for your insight and help with this... saved me a lot of money!