Patching concrete

[Kevin54]

Heres the poop....When I tore a wall out I also tore the foundation out underneath (1 course of block) which leaves me with a 4" wide and 4"-6" depth x 17' long trench. If I get bags of Sakrete to mix and fill it, should I use some kind of a bonding agent on the old concrete to get it to stick, or would I be okay by just dampening it down and filling it.

If it needs to use a bonding agent, what it the stuff called and does Lowes carry it?

 

[babzog]

I busted out a section of my garage floor a couple of years ago to repair the leaking electrical service entrance to the basement (builder's idea of sealing the hole was to jam a stick in and then backfill. ) At the same time, I was pouring a base for a tower I was putting up so I just called in the redi-mix concrete truck to pour the right mixes for each. When we did the garage, I'd already (like, a night or two before) hosed off the concrete edges to get the dust off and then we just poured, so the edges would have been dry. Still holding fast today.

Now, at the time, it never occured to me to saw clean edges and then bust out the 'crete. I just rented the jackhammer and went to town, following a line I'd layed down. So the hole was roughly square-ish but ragged... I guess the upside is lots of gripping surface, but not the cleanest finish (though it actually came out looking pretty good, all things considered, concrete can be feathered in quite well.)

 

[p_mori7]

i would drill some alternating holes every 12" on either side to partially drive in some long Tapcon screws, that way the new concrete strip will have something to "grip" to and not wanna move up/down independantly of the existing halves.

 

[mdbeck1]

i would drill some alternating holes every 12" on either side to partially drive in some long Tapcon screws, that way the new concrete strip will have something to "grip" to and not wanna move up/down independantly of the existing halves.

According to my buddy the concrete guy you're not supposed to tie BOTH of those floors together like that. It will cause a crack somewhere in the middle (and ragged). Better to put a piece of expansion joint in on one side (or at least not put the tapcons in on one side).

 

[tncatadjuster]

Wet it down if its dry, place a rebar in the center and make you mix dead on. Work it in, strike it off and keep it from drying out. Shrinkage is going to be your problem. It will form two small cracks down the sides, and possibly some crosswise. There is not much mass to it, so it will want to dry out quickly. When you coat it wait at least 28 days.

You could do a fancy job, but it would be expensive, and you would still have one expansion joint.

Should be no problem.

 

[cyamaha2007]

I patch and quality control concrete for a living. I would do a expansion joint and fill it. For best results i would cut the slab and make the gap wider like 1 foot it would be stonger and hold up better.

 

[Kevin54]

I really hate to cut out the slab and go to the expense of pouring new at the moment. One thing I do have to my advantage is that there is still cement block under where it needs filled. I think I'll try wetting it down and go that route for the time being. If it doesn't work out then I'm out a few bags of cement, rebar, and labor.

 

[red]

Kevin54 they do sell a concrete bonding agent at Lowes and Home Depot. It's white in color and needs to dry for about an hour. I would wet down the area before the "pour" and keep it soaking wet for at least 72hrs. (longer the better concrete continues to bond and strengthen as along as there is moisture present) After a week I would use a diamond blade and cut a joint along one of the edges. Some guys actually chisel (like undercut) the side of the slab to give the concrete something to "grab" to. When mixing the concrete less water the better! Good Luck! -Ed

 

[rieferman]

My first thought seeing the picture was that you could put a nice drain along that entire length.. would fill the spot nicely and easily and provide a useful feature all in one. But that doesn't answer your question (and I don't know the answer, sorry!)

edit: but if it were me, I'd do exactly what you just wrote.. Really, worst that will happen is it'll crack at some point. Oh well, for how inexpensive the solution is, and how easy it is to mix a few bags, you won't lose sleep.

side note, seems like we should all own one of those little mini mixers.. the ones with the wheel barrow style handles.

 

[jct]

Why fill it only to tear it out when it cracks later? At the least you need an expansion joint; I'd consider keylock as well.