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My garage floor is cracked & heaving near the asphalt apron. I will need to cut out the apron and get it properly replaced, but my immediate concern is the cement with the cold weather coming.

Can I simply remove the heaving cement, clean, se something like Sika bonding agent, and pour new concrete? I've seen backer rods and don't know if they're appropriate for this job... I pulled out a chunk and can see the broken peices will be quite deep. Also, what should I use to create the new joint at the asphalt?

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    Welcome to DIYSE. It's not really clear what you're asking. Is your question about cold weather, bonding something to something, sealing joints, or what? Please revise to clarify. Frankly, resolving the reason for the heave would be my first priority. – isherwood Sep 13 '19 at 15:10
  • So far as backer rod is concerned: it's really just a filler. Good caulks and sealants are expensive; it's costly to fill a large gap with those products. They also may not cure properly if they're applied too thickly. Backer rod exists to take up part of the volume so that less caulk/sealant is required and so that its thickness remains within manufacturer spec (while reading the product directions look for language like "use for gaps up to 1/4," or similar). – Greg Hill Sep 13 '19 at 15:47
  • By "backer rods" do you mean re-bar embedded in the concrete by chance? – Greg Nickoloff Sep 13 '19 at 20:21
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At this stage you can only try to keep it from getting worse. heaving is caused by the freeze thaw cycle. You can either keep the area warm or keep it dry. Often neither is practical.

Keeping it dry requires figuring out how water gets to the area below the concrete and stopping that flow. Water is very clever, and may be moving in after getting in elsewhere, but my first guess is the crack between the curb and the garage slab, and the one between the asphalt and the kerb. Backer rod and silicon grout come to mind.

At the core you have a bad installation. The curb has heaved, but not the slab. Fixing it is going to be expensive. Unless there are signs of problems elsewhere, I'd be tempted to live with it. Check the entire garage foundation to see if there are gaps opening anywhere else.

You can do a cosmetic repair. Rent a jack hammer to take off the protruding bits and about 1/2 to 3/4" more, do surface prep, and use a concrete patching compound to make it flush again. Finish by sealing the cracks with a combination of backer rod. A grout seal will accommodate something like half its width in moving. E.g., if you have 1/4" wide bead of grout, the two surfaces can shift something like 1/8" before the seal breaks. So a wide seal will help you here. Take this into account when you do the patch. You may want so preserve space for this.

Also, save a bunch of chips you removed from the prep. You can use that on top of the ground to partially colour match the floor.

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