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Placing Gravel on Previously Compacted Material

Placing Gravel on Previously Compacted Material

(OP)
Hello all

Is there any standard on placing gravel (not frozen) onto clay that has been scarified and compacted previously (in warm conditions) while the air temperature is around -15C? Most of the responses have to do with placing frozen material down or on top of natural sub grade but I may have missed something so forgive me if that is this case.

I appreciate any help!

RE: Placing Gravel on Previously Compacted Material

Don't know of particular standards, but keep in mind your clayey substrate is falsely stable when frozen. Will thaw and allow gravel to mix when softened. You might consider a geotextile separation between the two.

RE: Placing Gravel on Previously Compacted Material

If the gravel material is not frozen you should be able to place it just like you normally would, the clay surface will be frozen and is not really the issue (right now). The bigger issue is at your temperatures you will struggle to apply moisture to the gravel material during placement so you may have some issues getting proper compaction. At a minimum anticipate some additional maintenance when everything thaws.

Will this road be paved with asphalt or remain a gravel road?

RE: Placing Gravel on Previously Compacted Material

(OP)
@Ron - There will be a layer of geotextile to separate the clay and gravel material.
@civilman72 - This will be a gravel road. As far as the moisture goes, we were thinking of spraying with hot/warm water in order to obtain compaction results before it freezes up. Is this a valid method?

RE: Placing Gravel on Previously Compacted Material

Placing any material,even if non-frost susceptible material, at an air temperature below about minus eleven C is asking for trouble. I have seen a lot of winter work done and it seems that below that temp, even if the fill is unfrozen when dug or loaded, just does not get compacted suitably. At minus six, C, they sometimes fail to meet specs. With strong wind blowing, the approx. limit temperature is even higher. At minus 15C it would not be expected that any spec for compaction will come out as passing, even if they rush to compact. Sorry.

RE: Placing Gravel on Previously Compacted Material

I knew a mine site - was there once - and they were using slurry sand to form a tailings dam . . . later they did an investigation (it is cold up there) and the samples were typically described as sandy ice - not sure what the road is for - but why not place a layer of fine rock fill to get through the winter and then do a proper job when the weather permits.

RE: Placing Gravel on Previously Compacted Material

Agree with OG. I would think at that temperature the thin layer of water you spray on the surface would freeze quickly and not properly soak the gravel material, thus offering little benefit during your compaction efforts. I would also think you would have issues with your water truck working properly for any extended period of time (i.e. nozzles freezing).

RE: Placing Gravel on Previously Compacted Material

agree on no water, i can't see any way this would not get messed up.

i will throw some devil's advocate stuff out there first

i don't know the contractual arrangements here, but the timing of the work will be a critical element. Contractors are notorious for going too fast except when perishable goods (concrete, asphalt, mortar) are present. you may find your specifications are inadequate because they haven't been tested by years of practice and there may be construction claims that haven't come up much. i can imagine a few.

it is dangerous to discuss "gravel" on the internet as this word means different things regionally.

how confident are you that the materials will come warm.... At -15C, i have to think you are preventing the top 5 feet of cut from being used at the bank, and where does that go.... then i wonder how long that excavation is open before next truck shows up... overnight.... Are trucks sleeping in garages... Once ice is made in the gravel, i doubt it can be converted back to water until spring in that environment.

all that said... if we are just talking about the gravel road surface that needs to be used this winter... i don't see any reason not to just have the soils guy periodically monitor temps coming in and just before compaction like it was asphalt testing. i would try to get the contract to include getting the road visited by a heavy roller and some truckloads of maintenance stone in the summer. i hope you proofrolled the finished clayey subgrade before the cold came and have stayed off it.

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