Washing sand?

[zmoz]

I have a big pile of 3/4 minus crushed gravel that I want to mix into concrete. Problem is it's REALLY dirty - has a lot of clay mixed in. The larger rocks are easy to clean - I throw them on top of a 1/2" metal screen to seperate the big from small, and rinse the larger peices of gravel.

I also want the big pile of sand that's left under my screen. I would guess it's at least 10% clay. I can't mix that into concrete.

How do I go about cleaning sand? I've tried small batches in a 5 gallon bucket, with maybe 1 gallon of sand, trying to rinse it with the hose. That would take FOREVER and thousands of gallons of water.

There has to be a better way. Anyone?

 

[jbooth]

You didn't say if you had a cement mixer. If you do, run the mixer with the sand and water and keep dumping the water until it is reasonably clean. Would work for your gravel too. I believe I would opt to buy clean sand and gravel if your location does not make it cost prohibitive.

 

[zmoz]

I believe I would opt to buy clean sand and gravel if your location does not make it cost prohibitive.

LOL. You have no idea how pissed I was when I went and found 2 dump truck loads of gravel so thick with mud it sticks together like concrete! I was not expecting SO much dirt, but, I already have many tons of it at this point and it was only $11/yard.

I don't have one yet, but I do plan on buying a mixer, so I'll give that a try.

 

[CurlyDave]

I am not convinced that the fines from 3/4 minus is equal to sand for the purpose of mixing concrete. A much wider range of sizes, more very fine material, and more angular form means it will require more portland cement in the mix.

Instead of becoming the concrete experimental station for your area just buy good clean sand and use the 3/4 minus for a gravel road somewhere. That application can take the 10% clay with no problem.

The investment of time and energy you will make in trying to clean this up is just not worth the price of fresh sand.

While you can probably screen out & wash the larger sizes, which will make good aggregate, the 3/4 minus is a product all by itself, generally used for the top surface of a gravel road, and it can also be used as a hard packing, relatively free draining, fill, although I think the clay you have would prevent this use.

Save the 3/4 minus for its intended purpose and get some new, clean aggregate.

 

[zmoz]

I am not convinced that the fines from 3/4 minus is equal to sand for the purpose of mixing concrete. A much wider range of sizes, more very fine material, and more angular form means it will require more portland cement in the mix.

Hmmm...why is that exactly? Mostly I'm harvesting the larger rocks, maybe 50% of the pile, for the floor in my barn, the sand, and some larger stuff is what's piling up around me.

I may further screen it to seperate any "rocks" from "sand". Maybe I'll use the sand for something else and the larger peices as small aggregate. I'm not building a foundation or anything, so my concrete doesn't need to be perfect - I need to make a couple hundred stepping stones for my yard, pour a pad in a small compressor shed, and fill some post holes.

The sand might still be good for adding to the floor in my barn, especially since it's angular, but I still don't want to bring that much dirt in. I got it from a guy who mines it about a mile away, aparently he just takes a chunk of his hillside and dumps it in a crusher - rocks, dirt, and all...

 

[CurlyDave]

The reason is that fines from 3/4 minus will have much more surface area than the same weight of sand. It will take more cement to coat that surface area.

Most of the sand I see and use is quite a bit coarser than the fines from 3/4 minus.