Walking On Air

Except I'm supposed to be walking on concrete.

This here is a section of the concrete walkway beside my house, right in front of my brand new and expertly installed car hole door.

I'm really not sure why it's a separate piece, although it's possible that the landing for the car hole door was poured first, and the concrete walkway was added afterwards. The two different slabs of concrete do look slightly different.

Anyway, it's unfortunately sitting at this jaunty angle, which just happens to be the perfect slope for twisting unsuspecting ankles.

Now I had initially considered the idea that I might just skim over the top of this with some fresh concrete, but that would require doing some form work to keep the edges nice and neat, and then I'd have to finish the new concrete surface to make it look pretty, and so on. Instead, I decided to try just pulling this slab out so I could backfill underneath it to bring it back up to level.

So step one: dig out the pea gravel around it.

Well, not just the pea gravel, but also the fossilized layer of dryer lint and other debris and detritus.

There's even some full on dryer sheets in there, which really makes me wonder how this house didn't burn down decades ago from a dryer lint fire.

Oh, and there was also this peculiar D6.

Apparently it's from backgammon, which surged to a peak of recent popularity in the mid 1960s through the 1970s before fading back into relative obscurity over the course of the 1980s.

But enough about the recent history of backgammon, back to the task at hand. The slab in question is just barely small enough to be lifted out by hand, which is what I did next.

And this of course revealed the cause of the slumping: moles. It's no surprise that they've been digging under these sidewalk slabs, and for the most part to no ill effect. But this slab was small enough to be able to sink into the undercut over time, after which the moles no doubt would dig their tunnel a little bit deeper, and so on and so on.

So something tells me this might not be the last time I need to jack up this slab.

But before I worry about jacking up the slab sometime in the future, I need to get on with jacking up the slab in the present, so let's mix up some concrete.

I'm going with a sand-mix again since I only need an inch or two of depth here, and I have a bag of sand and a bag of cement left over from skimming the sidewalk on the other side of the house a while back.

Pro-tip: don't keep bags of cement laying around. Even in a dry climate they'll pick up moisture from the air and start to go off. Luckily I don't need any particular strength from this pour; I really only need it to be "fill that I don't need to worry about compacting" so this will still do the job just nicely.

I needed about 1/2 a cubic foot of concrete to bring the slab back up to roughly level, so I started with a gallon of water in my bucket and used my amazing paddle mixer in my rotary hammer to mix. This time I went with 3 scoops of sand for every 1 scoop of cement until I got a nice consistency, though it wasn't feeling as sticky as I wanted so I splashed in a bit more water at the end and added another scoop or two of cement.

Well it certainly looks the part. I sprayed down the dirt before dumping this mix in to keep it from sucking away all the moisture, then I spread it out and cut some peaks and valleys into it with my hoe.

This helps the concrete spread out evenly under the slab without trapping too many huge air pockets.

Then all I needed to do was tip the slab back into place.

And pack it with pea gravel to keep it from moving.

It's already pretty much fine to walk on right away, but I'll give it a good 24 hours to set up nice and stiff before putting too much weight on it. The good news is that I calculated the concrete volume pretty much spot on, so the slab is back up to basically level again.

Or at least as level as any of these slab sections are.