Filling garage pit need concrete advice

[Bucklagrim]

I bought a new home a few months back and to my surprise it came with a garage pit. At first I thought I would use it, but after some consideration I realized that it would only be usefull for oil changes and greasing suspension components. All other services would be complicated by its existence. So I had it filled with #73 stone and started to get estimates for capping the pit with concrete. According to one guy who gave me a bid I should have had the pit compacted as it was being filled and compaction now would do little other than compacting the top foot or so. So what do I do now???????

According to the two guys I've talked to I can either...

1. Soak pit slowly with water to allow it to settle

2. Compact and don't worry about it because 4" of crete tied into the existing
slab should be fine spanning any voids and due to the fact that the stone was slung into the hole its already compacted.

I have no idea what to do. I would appreciate any help those in the know might provide.

Pics to follow

 

[Chris705]

Not familiar with #73 stone. Is it a graded mixture of fines and stone? Not sure adding water at this point would be helpful, is there drain at the bottom. If #73 is a graded mixture of stone and fines it will need to be compacted. Is it possible to remove half the depth of the fill, rent a plate compactor, compact half the fill for an extended time and then add lifts of the removed fill 8" at a time and compact each layer... That is how I'd tackle it.

 

[Tink]

You could leave several access holes through the slab to add filler if it settles.

 

[matt_i]

Its not that deep. Get out a shovel and dig out the stone. Rent a jumping jack and not a plate compactor. That's a tool designed to work in a narrow trench, not a wide floor-area. Fill in 6" lifts and compact it. One day rental if you do the dig prep first.

In my opinion the slab needs to be edge-drilled for #4 = 1/2" rebar to keep the new patch aligned with the old slab.

 

[Strouty]

For future people in a situation like this, you should use flowable fill, it is much better and gets you very close to 100% compaction without any manual compaction. The local concrete company would deliver it and pour it in. It fills voids nicely and when it is hard, you can still dig it with a shovel. It is essentially sand with a bit of cement.

In your current situation, you could dig down a ways, add water as they said and then compact it as best you can in 4" lifts. Most likely 4" will be fine with voids under it, but that hollow sound would drive me crazy. As Tink said, you could always pump grout in through holes when (or if) it gets a void under it. I would drill them afterwards instead of leaving access holes. Just make a designated area that you know there won't be rebar to hit with the drill.

 

[Bucklagrim]

Here's some pics of the process thus far.

 

[404]

Bring the stone up to the top flush and just walk on that. If fancy is needed, cap with plywood.

 

[404]

Stone looks like crusher run.

 

[yyc_ranger_4x4]

From filling in my grandfathers old pit....
-fill in stages about 1' at a time,
-compact with a jumping jack (or plate ******** if thats all you have),
-drill and pin existing concrete with 1/2" rebar on 18"-24" centers
-rebar your new concrete and tie to pins
-prep edges with adhesion promoter,
-pour your concrete.

 

[Strouty]

So the bottom was dirt?

I would dig out about a third of that stone, just put it on a tarp near the hole, then compact as best you can, spray water on it (think sprinkler not stream) and then compact the rest in four inch lifts. Then drill the sides for #4 bar and pour 6" of concrete, you are going to be into a minimum charge anyways, might as well use all the concrete you can.

 

[Wanna Ride]

Maybe you have a perfectly good reason, but I have to ask... why did you fill it instead of just buying some steel plate that you could slide off, and take advantage of the pit when necessary?

 

[Bucklagrim]

Thanks for all the replies. The reason I didn't leave it and improvise a cover is due to possible liability concerns as this place may or not become a rental. I also didn't want the added hasle of having to drag jacks over grip strut or plate. I really want to move into this place as its on 2 acres, but the better half is undecided. The house needs some work.

So it seems like the consensus is remove stone and compact. Not what I wanted to hear, especially after paying the extra charge to have the stone directly slung into the pit.

 

[Rookie2]

That's what we call 'dust' , if you level it , it will settle very little , just walk away for a month or tamp it down if you are in a rush. Find someone pouring near by and set up with them for a 1/3 yard and to finish it.

Don't add water, it would take years to evaporate. place a sheet of plastic under the new pour.

 

[Bucklagrim]

That's what we call 'dust' , if you level it , it will settle very little , just walk away for a month or tamp it down if you are in a rush. Find someone pouring near by and set up with them for a 1/3 yard and to finish it.

Don't add water, it would take years to evaporate. place a sheet of plastic under the new pour.

I think I will do that, level and let it sit for the winter, tamp and pour come spring. I guess there is no need to rush and cap it. Driving on it for a couple of months will probably aid in it settling.

I also thought that adding water was a bad idea. Especially since I didn't notice a drain before filling. Thanks guys for all the help and additional perspectives.

 

[mrvm]

Maybe you have a perfectly good reason, but I have to ask... why did you fill it instead of just buying some steel plate that you could slide off, and take advantage of the pit when necessary?

+1....wish I had a service pit because I would bolt the steel plate down when not in use

 

[NUTTSGT]

I would have compacted it as I filled the hole and would still do that after shoveling some of it back out.

One thing that would worry me is the edges. I'd guess they will only be 1 1/2" thick as I would also have to guess that there would have been 2x planking that was placed over it when not in use.

If they are only 1 1/2" thick, I would cut the concrete edge (under where the plank would sit) and knock it off with a sledge.

 

[andersen24]

I had a pit at my rental and filled it for the exact same reason you did. I had everyone tell me about the same things.......all I did was fill it up with broken cinder blocks and filled it with concrete. That was 16 years ago and it is still perfect.

 

[Daniel Dudley]

I would rent a jumping jack tamper, and tamp it as it lays. A jumping jack is a very powerful tool, and you can tamp it for 30 or 40 minutes. There is often what is ideal, and what will work. tamping the **** out of that will work.

Pinning it with rebar would be a good idea.