Question about using concrete

[Ed62]

Last January or February when we had a ton of snow melt, we had a water leak in the basement. The ground was frozen, except right next to the house. So the water couldn't go anywhere except where the ground was not frozen.

Our driveway is about 3 feet from the side of the house. There is about an 18" wide concrete walkway next to the driveway, and about 18" of ground between the walkway and the house, which is currently being used for flowers. I'm thinking about pouring concrete from the house, all the way to the driveway. This would mean the sidewalk would be covered with new concrete. My question is this. Would I have to treat the existing sidewalk with something, for the new concrete to bond to it, thereby creating a seal between the two? Or would just pouring concrete over the sidewalk do the trick? (Yes, I did seal the blocks in the basement, but I want to be safe).

Ed

[Uncle Cracker]

How thick will the new concrete be over the existing sidewalk?

Also, will this leave you with drainage issues? Impermeable surfaces should slope away from the house.

[chopnhack]

They do make a latex binder that you can paint on to the old concrete or mix into the new concrete. You may also want to clean or acid etch the old concrete, even scarify so the two will bond well. As Uncle C mentioned, alot will have to do with the thickness of the overcoat.

[Ed62]

We've been here for 19 years, and this is the only time we had been flooded like that. The whole neighborhood was flooded.

Everything slopes away from the house, but when you have 2" or 3" of water standing, that doesn't help much. The main problem is that the ground thaws quicker next to the house, and the rest is still frozen.

I thought I'd bring the concrete to the bottom edge of the basement windows, and slope it to the driveway. The thickest part would be about 3" thick, and the thinnest would be maybe 1" or so. Thanks for the replies.

Ed

[jking]

So, the thickness over the sidewalk would be 1"?

[gjat]

Ed,
Yes you can put a 1" to greater on-top of existing concrete. A few points to consider.
1- Order concrete with fiber. It will help hold everything together so you don't get random cracks.
2- Match perpendicular expansion joints and relief cuts to so upper layer will expand/contract with lower.
3- Acid etch the existing concrete for good bond.
4- Dampen the existing concrete right before you pour for good bond.
5- Put expansion joint material along side where you butt up against the house. Again, this is to match expansion/contraction with lower. You can seal this afterwards.
6- If possible, over-pour the outside width of sidewalk about 2" so you don't have an exposed joint at ground to minimize water between the layers.

[woodturner]

Would I have to treat the existing sidewalk with something, for the new concrete to bond to it, thereby creating a seal between the two? Or would just pouring concrete over the sidewalk do the trick?

As others have mentioned, you can bond new concrete to old. However, it often doesn't work well. If you can make the new concrete a little thicker, say 2" to 3", I would be more inclined to put pea gravel over the old concrete to keep the new concrete from bonding to it and so they can move differentially to each other.

That's the basic problem - the new concrete will move with temperature and moisture at a different rate than the old concrete, so pretty much whatever you do won't hold.

One alternative that might work for you would be to use the concrete overlay material to cover the old concrete. It's applied in a thin layer and is purportedly strong enough to use for driveways.

[L. D. Jeffries]

That binder you paint on concrete is called by most cement people; "Moose Milk"

[Ed62]

Thanks for all the replies. This is the place to get answers.

Ed

[newood2]

All new concrete 3" thick minimum. Remove the old stuff. A much better fix.
Howie