Has anyone ever made their own Concrete?

[bandit67]

I am thinking about buying Portland Cement, but rather than buying tons of sand and gravel, using excavated dirt from my property. The dirt is sandy with decomposed granite and gravel, and I could buy a small amount of clean sand to supplement, if need be.

I'm no geologist, but it seems like it might be good enough to make concrete for dog kennels, patios, steps, maybe even parking pads, etc. I've used the fill to backfill holes for wood fence posts, and it compacts well, and the posts don't budge. I do know a former geologist that lives nearby, so I may bounce this off of him, but I don't know how well versed he is as far as concrete is concerned.

Has anyone done this before? If so, how did it turn out? Thoughts, ideas, comments?

 

[firefighter9208]

I'm not geologist, ect.... , but I don't think it will work. Concrete cures from a chemical reaction. Basically my understanding is the sand and gravel are binding agents. I have also heard to use clean water to make concrete. As in if you wouldn't drink it don't use it. Sand and gravel aren't that expensive anyway.

Chris

 

[EddieWalker]

It should work to a degree. The problem you will have is stregth. Since you are not using consitant materials, dirty sand with some amount of dirt mixed into it, you will end up with a much weaker mixture. Most people don't need 4,000 psi concrete for a pad to walk on, so if you are at 1,000 psi, it should be strong enough. If it fails, you will just have allot of cracks.

To add strength, you can add more Portland Cement to the mix. You can also add rebar and/or more rebar at a closer spacing. Instead of 2ft centers, you can put rebar in at 1 ft centers.

For what it's worth, I question the savings you will see from doing this, but then again, I don't know what your sand/gravel is like that you are planning on using.

First thing that you should do it seperate the rock from the sand with a screen. Then work on cleaning the sand to a clean as possible. When you have your seperate piles, then mix it in the proper ratio. This will at least give you some consistancy in your mix.

The Romans were doing this thousands of years ago, it hasn't changed allot since then. Especially if you are not going to build something on top of it. With out a load, you can mix Portland Cement with dirt and get a solid surface.

Eddie

 

[zeuspaul]

I have made non structural concrete with decomposed granite from my property. It works well but I don't know how strong it is.

Cement is the binding agent. The concrete won't be stronger than your aggregate (sand and rock).

If there are a lot of fines in your sand/DG mix you would need more cement in the mix as the cement gets *used up* quicker on the fines.

You may have impurities in the sand/DG mix which may adversely react with the cement over time.

Zeuspaul

Edit, Eddie is quick!!

 

[bandit67]

It may end up being more trouble than it's worth, and not so much as a savings, but it would be 'neat' to be able to say I made the non-structural concrete pads with some on-site materials.

I'd think there would be a smaller ratio of fines than your typical purchased mixes just because I don't think I'd want to spend too much time sifting, but aggregate is good, and I would probably bump up the portland cement ratio to increase strength to make up for the 'unknowns'.

I did find some info online on making your own "green" mixtures, which adds other aggregates into the mixes in smaller ratios, to cut down on 'consumables'. Fly ash, glass dust, recycled concrete, etc. Sounded interesting. https://www.concretecountertops.net...make-environmentally-friendlier-concrete.html

 

[dfkrug]

BANDIT:

Do a search for "rammed earth". This method of bldg construction uses
dirt, suplemented with portland cement and rebar. Not just any dirt, but
maybe yours is good enough.

A few things to remember about portland-based concrete: good concrete
is slightly alkaline, which protects the rebar from rusting. So acidic soil
would be bad. Also, sulphur compounds degrade concrete strength.

Good luck.

 

[bandit67]

Also, sulphur compounds degrade concrete strength.

This could be the straw that breaks the camel's back. I believe there is some amount of sulfur based on odors I encountered when digging through the decomposed granite pockets last fall.

A buddy in the area tried making his own concrete with on-site sand, and noticed that it was significantly weaker than the bagged stuff, but I don't know how much he bumped up the portland cement ratio.

Oh well, I guess I'll just go ahead and buy all the materials. By the time I'm done testing the soil, sifting, etc., I'll probably end up costing myself a bunch more money and time.

That's ok, because I should be able to recycle plenty of dead/dying/fallen trees off mine and my neighbors properties to get plenty of wood for trimwork, railings, mantles, etc for the house.

 

[zeuspaul]

Portland cement - Wikipedia, the free encyclopedia


Type V is used where sulfate resistance is important. Its typical compound composition is:
38% (C3S), 43% (C2S), 4% (C3A), 9% (C4AF), 1.9% MgO, 1.8% (SO3), 0.9% Ignition loss, and 0.8% free CaO.
This cement has a very low (C3A) composition which accounts for its high sulfate resistance. The maximum content of (C3A) allowed is five percent for Type V Portland cement. Another limitation is that the (C4AF) + 2(C3A) composition cannot exceed twenty percent. This type is used in concrete that is to be exposed to alkali soil and ground water sulfates which react with (C3A) causing disruptive expansion. It is unavailable in many places although its use is common in the western United States and Canada. As with Type IV, Type V Portland cement has mainly been supplanted by the use of ordinary cement with added ground granulated blast furnace slag or tertiary blended cements containing slag and fly ash.

 

[Egon]

Go to the Portland Cement Association site and get all the information you want plus more!

 

[PitbullMidwest]

I am thinking about buying Portland Cement, but rather than buying tons of sand and gravel, using excavated dirt from my property. The dirt is sandy with decomposed granite and gravel, and I could buy a small amount of clean sand to supplement, if need be.

I'm no geologist, but it seems like it might be good enough to make concrete for dog kennels, patios, steps, maybe even parking pads, etc. I've used the fill to backfill holes for wood fence posts, and it compacts well, and the posts don't budge. I do know a former geologist that lives nearby, so I may bounce this off of him, but I don't know how well versed he is as far as concrete is concerned.

Has anyone done this before? If so, how did it turn out? Thoughts, ideas, comments?

I've spoken to quite a few missionaries who build with "soilcrete" in other countries with great success. Do a Google search for soilcrete, earthcrete or dirtcrete.