Stone tamping

[Calhouncm]

Hello,

I built a 36x48 pole barn style garage last summer and am looking to pour the floor this summer. What I am trying to figure out is how much tamping or time I need to put in to the stone that I put in before pouring. On one end of the garage I have probably three feet of gravel to get to the height I need for the floor. The other end only needed about a foot or a little less. Reason I had to put so much there was the grade of the property. I did not tamp all the way through and still need to tamp. I plan on doing this but was also considering using a sprinkler to get the stone/gravel to sift more down through on it's own. As I said I did not tamp but I did have a skid steer leveling out at different heights as the stone worked it's way up which would have done some packing. I live in New York State so the stone did sit through a winter in the garage already which the freezing of the winter should have helped shift already. I am just trying to figure out the best way at this point to ensure I have a solid base before pouring the concrete.

Thanks for any input

 

[RivennHewn]

At 3' deep, even a jumping jack style compactor won't touch the lower stuff.

A hoe pac, a compactor on a backhoe/excavator, will be the only way to be sure you get 100%.

What type of stone did you use? Crushed w/ fines, or drain rock?

 

[Delta74]

I have to agree with the above, at 3 feet, you would need some pretty damn big compactors in there to get that down, for a garage floor I don't think it would be that bad, but I would expect it to shift and start cracking shortly after pouring.

I know at work for me ( huge Industrial sites ) 6 inches is the max allowed between compacting, and tested each level.

personally I would be a lot more comfortable digging out 2 feet, packing, and adding in 8-10 inches at a time between compacting it with a little Jumper or man sized Wack a pack thing.

this is out side my experience ( just a dumb electrician, this is the Civil department's area ) best bet, ask the concrete guys, they will tell you what they want if they are going to offer any kind of a warranty on work.

 

[Reitwagen]

I was in the same boat as you. I rented a plate compactor and one of these for 200.00 per day. That font roller vibrates like a compactor. I used it to do the center and the plate compactor for the edges. Well worth the money. There is about 2 1/2 feet of sand in there for fill plus about 8 inches of crushed gravel on top of it. It was all added in 1 foot increments.

 

[Bondo]

Ayuh,.... Bein' in the Blacktop biz, We compact every 2"/4" lift for full compaction,...

Even a 10 ton vibratory drum roller will only compact, Maybe 6" down,...

 

[ConCretin]

The answer to your question might vary depending on the nature of the material. You refer to it as stone and gravel interchangably. Those terms have different meanings in different part of the country.

Up here 'gravel' refers to a material having a wide gradation of materials from fines up through stone of 2" or greater. This material must be compacted in lifts at the proper moisture level to acheive maximum compaction.

If you placed a washed, crushed stone with no fines, that's different. This material can be placed with little or no compaction required.

 

[SunsetsAndFriends]

The answer to your question might vary depending on the nature of the material. You refer to it as stone and gravel interchangably. Those terms have different meanings in different part of the country.

Up here 'gravel' refers to a material having a wide gradation of materials from fines up through stone of 2" or greater. This material must be compacted in lifts at the proper moisture level to acheive maximum compaction.

If you placed a washed, crushed stone with no fines, that's different. This material can be placed with little or no compaction required.

LLWillysfan is correct about this. Stone, without fines, can be placed with little compaction. When compacting, you're really primarily locking the surface rock to make it more durable for driving/walking over. I'm in road construction. We often use stone in places where the earth is too soft to support the loads that roadways and road traffic, including other natural forces, place on the subsoil. In those cases we dig out the subsoil to the engineered depth and place stone, often 3" select. The 3" select locks agains each other with little tamping needed, creating a kind of matrix (lattice) that supports itself and the loads above. Keep in mind that we always tamp but the primary compaction point occurs where the stone meets the subgrade.

It really is kind of amazing how this works. I've been involved in roadwork in a city in WI where the earth under the roads is like a waterbed. The engineers have us use similar techniques as above or using potash. The results are startling effective.

Now, despite what I say above, if this were my project, I would still be inclined to place stone in layers and compact each layer, especially the first few layers because while the stone may not compact, if at all, the subsoil below may be a different story. The subsoil may compact in varying amounts depending on composition in any particular area. I believe one can never really go wrong by compacting.

Considering the cost of concrete, you may want to look at machine rental options for accomplishing compaction. This would involve removing some of the stone, compacting, and placing stone with compaction in layers. Or consult an engineer in your area. The engineer might only cost a couple of hundred dollars and be able to confirm the need for the extra work or not. Good insurance.

 

[Autorotica]

Did I miss someone responding to the OP's question if wetting the stone or fill material would help with getting it settled?

Chris

 

[ConCretin]

Chris, I think the question was answered albeit in a round about way. If the material is gravel (with fines), it will need to be excavated and re-placed in lifts using mechanical compaction. If its washed stone, he's probably OK although some additional compaction would be good insurance. No one, including myself would rely on simply watering the fill to achieve compaction.

 

[Autorotica]

Chris, I think the question was answered albeit in a round about way. If the material is gravel (with fines), it will need to be excavated and re-placed in lifts using mechanical compaction. If its washed stone, he's probably OK although some additional compaction would be good insurance. No one, including myself would rely on simply watering the fill to achieve compaction.

Thanks...

Chris