Proper compacting techniques for sand
Tennessee
| Posted in Construction Techniques on
I am replacing the concrete floor in my 80 year old barn. I removed the old concrete and then removed the clay below it. In some places I removed 3′-4′ of clay.
I then put sand back in to replace the clay. I did not compact the sand as I put it in.
Our two horses have been compacting the sand for about 4 weeks, one foot (hoof) at a time.
Is this sufficient compacting, or do I have to remove some of it and compact it in 1′-2′ layers before I put the new concrete in?
Thank you in advance for your assistance.
Replies
Ideally it should have been compacted in lifts, but to dig out 3-4' of sand and start over is probably not what you want to hear. Try flooding it with water. Wait a day or two and then run a compactor over it.
Remove all organic matter before proceeding.
Any barn cats assisting with the compacting?
Joe H
Ditto on removing any "organic material" that your horses may have added. ;-) Really though I think sand would be mostly self compacting - although admittedly we don't use sand under concrete around here so I don't really know. Ask brownbag - he knows. I think he said something about flooding the sand with water to get it to compact - although I guess you would then have to let it dry out at least partially, and if it is sitting in a "pan of clay" that could take a while... I'm sure it also depends on the type of sand - some sand is "sharper" than others.
Tennessee,
The horses, unfortunately, have not been trained to do a quality job. They just won't walk every square foot the same amount.
Fisrt, as several people have advised, remove all organic material.
Second, allow all horsey liquids to dry completely.
Third, on this very dry sand base, run a 'Jumping Jack' type compactor over the entire area. This will compact the top few inches and give you a start to work from.
Fourth, using the same JJ compactor, start over, but this time hold the JJ in one spot until that spot is as hard as it gets. The foot of the compactor will probably be buried 3"-6" by the time that spot is done. Move the compactor out of that footprint and deep compact the next footprint. You should leave about 6"-8" between footprints.
Fifth, set up enough sprinklers to cover the entire floor and add 2"-3" water per foot of sand depth. You can use coffee cans to measure the water. You will have to measure in zones, adding more water where the sand is deeper.
Sixth, this is probably the second day. After you have no standing water to a depth of 1', dig holes to make sure, run the JJ in a normal way over the floor.
Finally, scrape and fill the sand base until it is completely flat and level, then use a 'Vibrating Foot' compactor to finish.
'Point Compacting,' step 4, can compact dry sand to a depth of 24"-30", but it leaves the top foot or so loose. Normal compacting damp sand, step 6, can compact to a depth of 8"-14", but it leaves the top few inches loose and the surface uneven. The final compaction with a VF will compact the very top and leave a smooth and flat surface for the concrete.
The cost will be two man days labor plus 1 1/2 day rental on the JJ and 1/2 day rent on the VF.
Sand is NOT the best base to try and compact. Straight Crusher Run, a mix of very fine dust to about 1 1/2" diameter gravel is the best, IMHO.
Hoping this helps ya,
SamT
flood it with water. about a 1000 gallons and be done with it.
had this same situation in shop. i had a 4 wheel drive truck,got inside the building and drove,spun tires,turned in figure 8's for about a hour,then put water on it for maybe 6 hours total. floor has no cracks 9 yrs later. plus it's fun trying to get the truck stuck!larry
hand me the chainsaw, i need to trim the casing just a hair.
As if you needed one more opinion <G>,
The more granular a material is, the better it will respond to vibration during compaction.
At one end of the scale, you have soils with a high silt-clay content; these need to be kneaded or pounded, hence the jumping jack or sheepsfoot or rubber-tire roller (in thin lifts)
at the other end of the scale you have granular soils -- like sand.
These want to be vibrated, and all soils will respond differently to different frequencies.
Moisture content is essential, fortunately with sand you have a wide range because there is no plasticity.
How does this apply to you?
The easiest and fastest way to compact an area like this, (especially as large as a barn) is go to your local rental yard, pick up either a small single-drum vibratory roller or a big skid steer with a virbatory smooth-drum roller attachment. They can easily hit 8,500 pounds dynamic, and you can vary the frequency with the throttle.
That will give you more than enough compaction, and it's fun.
With all due respect to previous posters, I can't imagine working in a few feet of sand with a jumping jack. That's not what the tool was made for.
And forget about the 180 pound vibrating plates. As Brownbagg has often correctly pointed out, they are worthless for anything but patching asphalt.
Thank you for the informative response, and thank you to all of the others who so generously provided input. The wealth of experience and knowledge on this listserve is awesome.
I don't know just yet how I am going to proceed --- still sorting out all of the options provided here.
I do know one thing though, and that is that I will consult this list before I start down the road on another project like this.
You're welcome.That's pretty much all I do for a living is dig up dirt and put it back.Used to do a lot of concrete, too, no more of that for me.So I've got the same feeling for this place -- I'm very grateful for all that I have learned from all of the folks here. It's like an on-line construction college.Beer and all. <G>
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
r u a feckless dastard?
I had to look that up in the dictionary.I sure hope not.
heh heh
I'm wondering how many dictionaries got opened with that.
r u a feckless dastard?
Are you the guy I remember who does roadwork and such up in the mid west someplace? I remember someone here who was quite knowledgable about compaction and site preparation.
We routinely pour concrete on top of what we call #67 washed stone - uncompacted. #67 is, I think 3/4" - 1.5" peices of crushed blue stone - I think it is actually granite. It is quite iregular and jaged in shape, though I would say, not really sharp. What do you think of this practice?
I think that if it works it's probably a good idea. <G>I rarely argue with success. Reminds me of an engineer who didn't want me to do something because even though it worked in practice, it didn't work in theory.